AN ABSTRACT OF THE THESIS OF
Roald N. Leif for the degree of Doctor of Philosophy in Oceanography presented on
July 23, 1993.
Title: Laboratory Simulated Hydrothermal Alteration of Sedimentary Organic Matter
from Guaymas Basin, Gulf of California
Redacted for Privacy
Abstract approved:
Bernd R. T. Simoneit
High temperature alteration of sedimentary organic matter associated with
marine hydrothermal systems involves complex physical and chemical processes that
are not easily measured in most natural systems. Many of these processes can be
evaluated indirectly by examining the geochemistry of the hydrothermal system in the
laboratory. In this investigation, an experimental organic geochemical approach to
studying pyrolysis of sedimentary organic matter is applied to the hydrothermal
system in the Guaymas Basin, Gulf of California.
A general survey of hydrothermal oils and extractable organic matter
(bitumen) in hydrothermally altered sediments identified several homologous series of
alkanones associated with a high temperature hydrothermal origin. The alkanones
range in carbon number from C11 to C30 with no carbon number preference. Alkan-2ones are in highest concentrations, with lower amounts of 3-, 4-, 5- (and higher)
homologs. The alkanones appear to be pyrolysis products synthesized under extreme
hydrothermal conditions.
Hydrous pyrolysis and confinement pyrolysis experiments were performed to
simulate thermally enhanced diagenetic and catagenetic changes in the immature
sedimentary organic matter. The extent of alteration was measured by monitoring the
n-alkanes, acyclic isoprenoids, steroid and triterpenoid biomarkers, polycyclic
aromatic hydrocarbons and alkanones. The results were compared to bitumen extracts
from sediments which have been naturally altered by a sill intrusion and accompanied
hydrothermal fluid flow. These pyrolysis experiments duplicated many of the organic
matter transformations observed in the natural system. Full hopane and sterane
maturation occurred after 48 hr in experiments at 330°C with low water/rock mass
ratios (0.29).
A variety of radical and ionic reactions are responsible for the organic
compound conversions which occur under extreme hydrothermal conditions. Short
duration pyrolysis experiments revealed that a portion of the hydrocarbons generated
from kerogen was observed to go through alkene intermediates, and the rate of alkene
isomerization was influenced by the ionic strength and catalytic mineral phases.
Confinement of the organic pyrolysate to the bulk sediment accelerated the rates of
the biomarker epimerization reactions, suggesting that these reactions are influenced
strongly by the association of the inorganic matrix, and that the relative rates of some
ionic and radical reactions can be influenced by the water/rock ratio during the
pyrolysis experiments.
©Copyright by Roald N. Leif
July 23, 1993
All Rights Reserved
LABORATORY SIMULATED HYDROTHERMAL ALTERATION OF
SEDIMENTARY ORGANIC MATTER FROM GUAYMAS BASIN, GULF OF
CALIFORNIA
by
Roald N. Leif
A THESIS
submitted to
Oregon State University
in partial fulfillment of
the requirement for the
degree of
Doctor of Philosophy
Completed July 23, 1993
Commencement June 1994
APPROVED:
Redacted for Privacy
Professor of Oceanic and Atmospheric Sciences in charge of major
Redacted for Privacy
Head of Departihent of Oceanic and Atmospheric Sciences
Redacted for Privacy
Dean of Graduate
Date thesis is presented
July 23. 1993
Typed by researcher for
Roald N. Leif
To my parents
and
Yen-Wen
ACKNOWLEDGMENTS
I would like to thank the individuals and organizations contributing to my
dissertation research. I thank Bernd Simoneit, my thesis advisor, for his guidance,
support and encouragement during my graduate career. I thank Fred Prahi for the
many useful discussions we had on this research. The suggestions to the thesis text by
Bob Collier, Jack Dymond, Chih-An Huh and Dave Mclntire is appreciated.
Special thanks go to Keith Kvenvolden, of the U. S. Geological Survey, for the
use of his Parr reaction vessel for our pyrolysis experiments. His interest and
enthusiasm in this research is gratefully acknowledged. Louis Gordon was very kind
and generous to allow me open use of his tools and laboratory equipment. I also have
special thanks to the many past and present members of the organic geochemistry lab
who I have worked with, especially Orest Kawka for teaching me the techniques of
good laboratory practice and the ways of the Finnigan GC-MS. My life was enriched
by all of the friends I have made in the department. I thank my parents for their love
and support through the years.
This work was supported by the National Science Foundation, Division of
Ocean Sciences (OCE-8601 316 and OCE-9002366), the National Aeronautics and
Space Administration (NAGW-2833), and the Donors of the Petroleum Research
Fund administered by the American Chemical Society.
TABLE OF CONTENTS
CHAPTER1 Introduction ....................................................................................
Survey of hydrothermal oils and sediment extracts from the Guaymas
Basin hydrothermal system ...........................................................
Simulated hydrothermal alteration of sedimentary organic matter by
laboratory hydrous pyrolysis ........................................................
CHAPTER 2 Survey of the Polar (NSO) Fraction of Seabed Oils and
SedimentExtracts .........................................................................
Abstract .....................................................................................................
Introduction ...............................................................................................
Experimental .............................................................................................
Samples .........................................................................................
Extraction and fractionation ..........................................................
Gas chromatography .....................................................................
Gas chromatography-mass spectrometry ......................................
Results and Discussion ..............................................................................
Seabedoils ....................................................................................
Downcore sediment extracts from DSDP Site 477 .......................
Downcore sediment extracts from DSDP Site 481A ....................
Conclusions ...............................................................................................
CHAPTER 3 Radical and Ionic Reactions During Hydrothermal Pyrolysis
of Organic Matter: Implications for the Simulation of
Geochemical Processes .................................................................
Abstract .....................................................................................................
Introduction ...............................................................................................
Experimental .............................................................................................
Chemicals and samples .................................................................
Hydrous pyrolysis experiments .....................................................
Extraction and fractionation .........................................................
Gaschromatography .....................................................................
Gas chromatography-mass spectrometry ......................................
Results and Discussion .............................................................................
11-C32H66 pyrolysis experiments ...................................................
Pyrolysis of 1,1 3-tetradecadiene, 1 -hexadecene and eicosane
inD2O ...............................................................................
Low density polyethylene pyrolysis .............................................
Pyrolysis of 1,1 3-tetradecadiene polymerization product ............
Messel shale H20 pyrolysis - repeat of Hoering (1984)
experiment .........................................................................
Messel shale H20 pyrolyses composition of aliphatic
molecularprobes ...............................................................
Messel shale D20 pyrolyses - composition of aliphatic
molecular probes ................................................................
Messel shale H2O and D2O pyrolyses composition of
aliphatic hydrocarbons released from kerogen ..................
Guaymas Basin sediment D20 pyrolysis - composition of
aliphatic molecular probes .................................................
I
3
4
10
11
12
13
13
13
14
14
15
15
17
18
22
58
59
60
63
63
63
63
64
64
65
65
66
66
67
67
68
68
68
69
Elemental sulfur D20 pyrolysis - composition of aliphatic
molecular probes ...............................................................
Conclusions ...............................................................................................
CHAPTER 4. Simulation of Thermally-Enhanced Diagenetic and
Catagenetic Transformations of Organic Matter in Surface
Sediments from the Southern Trough of Guaymas Basin .............
Abstract.....................................................................................................
Introduction ...............................................................................................
Experimental.............................................................................................
Samples .........................................................................................
Hydrous pyrolysis experiments .....................................................
Extraction and fractionation ..........................................................
Gas chromatography .....................................................................
Gas chromatography-mass spectrometry ......................................
Results and Discussion ..............................................................................
Volatile hydrocarbons ...................................................................
n-Alkanes ......................................................................................
Triterpenoid hydrocarbons ............................................................
Polycyclic aromatic hydrocarbons ................................................
Diels' hydrocarbon ........................................................................
Ketones.........................................................................................
Conclusions ...............................................................................................
70
74
124
125
126
127
127
127
127
128
128
129
129
129
129
130
130
131
133
CHAPTER 5. Simulation of Hydrothermal Catagenetic Transformations of
Organic Matter in Surface and Downcore Sediments from the
Northern Trough of Guaymas Basin ..............................................145
Abstract ..................................................................................................... 146
Introduction ............................................................................................... 147
150
Experimental .............................................................................................
150
Samples .........................................................................................
Hydrous pyrolysis experiments ..................................................... 150
Extraction and fractionation .......................................................... 150
Gaschromatography ..................................................................... 150
Gas chromatography-mass spectrometry ...................................... 151
Results and Discussion .............................................................................. 152
AII-112-29PC-5 ...........................................................................
481 A-8-7 (top of pipe) ..................................................................
481A-22-7 (top of pipe) ................................................................
Effects of time on the pyrolysates .................................................
Effects of depth on the pyrolysates ...............................................
Conclusions ...............................................................................................
CHAPTER 6. A Proposed Chemical Pathway for the Origin of Ketones
in Oils and Sediment Extracts from the Guaymas Basin
Hydrothermal System....................................................................
Abstract .....................................................................................................
Introduction ...............................................................................................
Experimental .............................................................................................
Sample ..........................................................................................
Hydrous pyrolysis experiments ....................................................
Extraction and fractionation .........................................................
152
153
154
155
156
158
181
182
183
184
184
184
184
Gas chromatography
Gas chromatography-mass spectrometry ......................................
Results and Discussion .............................................................................
Chromatographic behavior of aliphatic ketones ...........................
Ketones in hydrothermal oils........................................................
Ketones from the hydrous pyrolysis of -C32H66 .........................
Ketones from the pyrolysis of aliphatic molecular probes
with Messel shale..............................................................
Proposed origin of ketones under natural and simulated
hydrothermal conditions ....................................................
Conclusions...............................................................................................
185
185
186
186
186
186
CHAPTER7. Conclusions ...................................................................................
198
REFERENCES .....................................................................................................
201
APPENDICES ......................................................................................................
The gas chromatograms for the seabed oils from the
Appendix 1
hydrothermal vents of Guaymas Basin, Gulf of
California..........................................................................
Appendix 2 The gas chromatograms for the downcore sediment
extracts from DSDP Site 477 of Guaymas Basin, Gulf
ofCalifornia ......................................................................
Appendix 3 The gas chromatograms for the downcore sediment
extracts from DSDP Site 481A of Guaymas Basin,
Gulf of California..............................................................
Appendix 4 The gas chromatograms from the pyrolysis
experiments on the North Rift surface sediment and
downcore sediments of DSDP Site 481 A, Guaymas
Basin, Gulf of California ...................................................
212
187
187
188
213
222
238
255
LIST OF FIGURES
Page
Figure
1.1.
Map of discovered submarine hydrothermal systems of the Eastern
Pacific (Von Damm, 1991) ........................................................................
1.2.
Map of the Guaymas Basin hydrothermal system, Gulf of California
(Gieskes et al., 1991) .................................................................................. 7
1.3.
Diagram showing the hydrothermal convection of seawater in a
sediment-covered spreading center (adapted from Scott, 1983;
Simoneit, 1985) .......................................................................................... 8
1.4.
Schematic version of hydrothermal systems in Guaymas Basin,
Gulf of California. C cold water advected down through fault zones.
H = hot water advected through sediments and fault zones. (Adapted
from Gieskes et al., 1982b) ........................................................................
6
9
2.1.
(a) Map of Gulf of California showing geographic location of the
sampling area, and
(b) Map of Guaymas Basin showing its two rifts, with locations of
DSDP Sites (Simoneit, 1991) ..................................................................... 29
2.2.
Bathymetric chart of the southern rift of Guaymas Basin with general
study area of Alvin dives during March, 1988. The transponder array
with its x,y coordinates is also indicated (Simoneit, unpublished
report, 1988) ...............................................................................................
30
2.3a.
Lithologic colunm for site DSDP Site 477, lowercase letters refer to
sample locations listed in Table 2.2a (Curray et al., 1982) ........................ 31
2.3b.
Lithologic column for site DSDP Site 481A, lowercase letters refer to
sample locations listed in Table 2.2b (Curray et al., 1982) ........................ 32
2.4.
Histograms of bulk class percentages for chimney samples
(a) 1 972-CH 1 and
(b) 1983-CHI ..............................................................................................
33
2.4.
Histograms of bulk class percentages for chimney samples
(c) 1984-CH1 and
(d) l984-CH2 .............................................................................................. 34
2.5.
Ternary diagram of the bulk compositions for seabed hydrothermal
oils. (adapted from Kawka and Simoneit, 1987) ....................................... 35
2.6.
2.7.
2.8.
2.9.
Gas chromatograms of 1972-CH1 Interior:
(a) aliphatic fraction;
(b) aromatic fraction;
(c) NSO fraction.
Numbers refer to carbon chain length of the -alkanes and ketones,
Pr = pristane, Ph = phytane, A = isoprenoid phenol (MW = 388),
B = isoprenoid phenol (MW = 402) ...........................................................
36
Gas chromatograms of 1972-CH1 Exterior:
(a) aliphatic fraction;
(b) aromatic fraction;
(c) NSO fraction.
Numbers refer to carbon chain length of the n-alkanes and ketones,
Pr = pristane, Ph = phytane, A isoprenoid phenol (MW = 388),
B = isoprenoid phenol (MW = 402) ...........................................................
37
NSO fraction of hydrothermal oil from the interior of vent I 972-CHI:
(a) reconstructed ion chromatogram (RIC);
(b) representative mass fragmentograms for ketones
(mlz 57 + 58 + 71 + 72) of oil covering the same scan range;
(c) expanded scale identifying resolved ketone isomers.
Numbers refer to carbon chain length ........................................................
38
NSO fraction of hydrothermal oil from the interior of vent 1 972-CH 1:
(a) representative mass fragmentogram for the isoprenoid phenol
compound A (mlz 122);
(b) representative mass fragmentogram for the isoprenoid phenol
compound B (mlz 136);
(c) representative mass fragmentogram for the isoprenoid phenol
compound C (m/z 150) ...............................................................................
39
2.10.
Mass spectra and proposed structures of isoprenoid phenols present in
NSO fraction of hydrothermal oil from the interior of vent 1 972-CH 1:
(a) compound A;
(b) compound B;
(c) compound C.
Mass spectra correspond to the peaks labeled in Fig. 2.9 ........................... 40
2.11.
Silylated NSO fraction of hydrothermal oil from the interior of vent
1972-CH1:
(a) representative mass fragmentogram for the isoprenoid phenol
compound N (nVz 194);
(b) representative mass fragmentogram for the isoprenoid phenol
compound B' (mlz 208);
(c) representative mass fragmentogram for the isoprenoid phenol
compound C' (mlz 222) ............................................................................... 41
2.12.
Mass spectra of silylated isoprenoid phenols present in NSO
fraction of hydrothermal oil from the interior of vent I 972-CH1:
(a) compound A';
(b) compound B';
(c) compound C'.
Mass spectra correspond to the peaks labeled in Fig. 2.11 ......................... 42
2.13.
Representative mass fragmentograms (Mt) for the silylated derivatives
of the extended C19 to C34 n-alkylphenols present in the NSO fraction
of hydrothermal oil 1972-CH1 Interior. Compounds A! and B' refer to
the isoprenoid phenols ................................................................................ 43
2.14.
Representative mass fragmentograms (M) for the silylated derivatives
of the extended C27 to C29 n-alkylphenols present in the NSO fraction
of hydrothermal oil 1 972-CH I Interior. Labeled in the figure are series
C,DandE ..................................................................................................
44
2.15.
Mass spectra of silylated -alkylpheno1s present in NSO fraction
of hydrothermal oil from the interior of vent 1 972-CH 1:
(a) compound Cl;
(b) compound C2;
(c) compound C3.
Mass spectra correspond to the peaks labeled in Fig. 2.14 ......................... 45
2.15.
Mass spectra of silylated n-alkylphenols present in NSO fraction
of hydrothermal oil from the interior of vent I 972-CH 1:
(d) compound Dl;
(e) compound D2;
(f) compound D3.
Mass spectra correspond to the peaks labeled in Fig. 2.14 ......................... 46
2.15.
Mass spectra of silylated -alky1phenols present in NSO fraction
of hydrothermal oil from the interior of vent 1 972-CH 1:
(g) compound El;
(h) compound E2;
(i) compound E3.
Mass spectra correspond to the peaks labeled in Fig. 2.14 ......................... 47
2.16.
Plots of molecular parameters versus depth in DSDP Leg 64 Hole 481 A:
(a) CPI vs. Depth, meters below sea floor (mbsf) and
(b) Pr/Ph vs. Depth (mbsf) .......................................................................... 48
2.17.
Representative mass fragmentograms m!z 191 for the
triterpenoid hydrocarbons in the bitumen of DSDP Leg 64 sediments:
(a) 481A-4-2 (93-98);
(b) 481A-8-7 (top of pipe);
(c) 48lA-12-4 (55-65);
(d) 481A-l3-2 (18-27) ................................................................................
49
2.17.
Representative mass fragmentograms mlz 191 for the
triterpenoid hydrocarbons in the bitumen of DSDP Leg 64 sediments:
(e) 481A-18-1 (30-32);
(f)481A-20-1 (110-115);
(g) 481A-22-7 (top of pipe);
(h) 481A-26-CC .......................................................................................... 50
2.18.
Representative mass fragmentograms (mlz 215, 217, 218, 257, 259) for
the steroid hydrocarbons in the bitumen of DSDP Leg 64 sediments:
(a) 481A-4--2 (93-98);
(b) 481A-8-7 (top of pipe);
(c) 481A-12-4 (55-65);
(d) 481A-13-2 (18-27) ................................................................................ 51
2.18.
Representative mass fragmentograms (mlz 215, 217, 218, 257, 259) for
the steroid hydrocarbons in the bitumen of DSDP Leg 64 sediments:
(e) 481A-18-1 (30-32);
(f) 481A-20-1 (110-115);
(g) 481A-22-7 (top of pipe);
(h) 481A-26-CC .......................................................................................... 52
2.19.
Histograms of the major aromatic compounds present in the bitumen of
DSDP Leg 64 sediments:
(a) 481A-4-2 (93-98);
(b) 481A-8-7 (top of pipe);
(c) 481A-12-4 (55-65);
(d) 481A-13-2 (18-27) ................................................................................ 53
2.19.
Histograms of the major aromatic compounds present in the bitumen of
DSDP Leg 64 sediments:
(e) 481A-18-1 (30-32);
(f) 481A-20-1 (110-115);
(g) 481 A-22-7 (top of pipe);
(h) 481A-26-CC .......................................................................................... 54
2.20.
Representative mass fragmentograms (m/z 57, 58, 71, 72) for the ketones
in the bitumen of DSDP Leg 64 sediments:
(a) 481A-4-2 (93-98);
(b) 481A-8-7 (top of pipe);
(c) 481A-12-4 (55-65);
55
(d) 481A-13-2 (18-27) ............................................
2.20.
Representative mass fragmentograms (rnlz 57, 58, 71, 72) for the ketones
in the bitumen of DSDP Leg 64 sediments:
(e) 481A-18-1 (30-32);
(f) 481A-20-1 (110-115);
(g) 481A-22-7 (top of pipe);
56
(h) 481 A-26-CC ......................................................
2.21.
Representative mass fragmentograms (mlz 122 and mlz 136) for the
isoprenoid phenols in the bitumen of DSDP Leg 64 sediments:
(a) 481A-12-4 (55-65) and
(b) 481A-18-1 (30-32) ................................................................................ 57
3.1.
Overall average distribution of deuterium substitution in -alkanes
from C17 to C29 generated from the D20 pyrolysis of Messel shale
(after Hoering, 1984) .................................................................................
79
3.2.
Distribution of the relative abundances of C13 ion fragments from
pristane generated in the Messel shale D2O pyrolysis
(after Hoering, 1984) .................................................................................. 80
3.3.
The partial mass spectrum of deuterated 2-methyiheptadecane which
was generated in the Messel shale D20 pyrolysis (Hoering, 1984) ...........
81
Distribution of deuterium substitution in the products of the molecular
probe experiments, 330°C for 72 h:
(a) pyrolysis of docosane and D20 and
(b) pyrolysis of 1 -octadecene and D20 (after Hoering, 1984) ...................
82
3.4.
3.5.
Set of reactions proposed by Hoering (1984) to explain the deuterium
exchange process, includes only free radical chemistry ............................. 83
3.6.
Set of reactions proposed by Ross (1992a) to explain the deuterium
exchange process, includes ionic and free radical chemistry ..................... 84
3.7.
Gas chromatograms of the total extracts from the hydrous pyrolysis
experiments of fl-C32H66 at 350°C:
(a) H20
(b) H2O fl-C32H66 - NaC1;
(c) H20 n-C32H66 HCI;
(d) H2O - n-C32H66 - NaOH;
(e) H20 n-C32H66 - NH4CI;
(f) H20 n-C32H66- Na2SO4;
(g) H20 fl-C32H66- Sulfur;
(h) H20 n-C32H66- Sulfide.
Numbers refer to carbon chain lengths of-alkanes .................................. 85
3.8.
Gas chromatograms of the H20 fl-C32H66 system:
(a) nonpolar fraction before catalytic hydrogenation and
(b) nonpolar fraction after catalytic hydrogenation.
Numbers refer to carbon chain lengths of -alkanes .................................. 86
3.9.
Gas chromatograms of the H20 n-C32H66 NaOH system:
(a) nonpolar fraction before catalytic hydrogenation and
(b) nonpolar fraction after catalytic hydrogenation.
Numbers refer to carbon chain lengths of -a1kanes ..................................
87
3.10.
3.11.
Gas chromatograms of the D20 -C32H66 system:
(a) nonpolar fraction;
(b) alkane fraction;
(c) alkene fraction;
(d) alkene fraction after catalytic hydrogenation.
Numbers refer to carbon chain lengths of -a1kanes ..................................
88
Mass spectra of fl-C1 -jH36 from the D20 n-C32H66 system:
(a) alkane fraction and
(b) hydrogenated alkene fraction ................................................................
89
3.12.
Gas chromatograms of the D20 -C32H66 NaOD system:
(a) nonpolar fraction;
(b) alkane fraction;
(c) alkene fraction;
(d) alkene fraction after catalytic hydrogenation.
Numbers refer to chain lengths of -a1kanes .............................................. 90
3.13.
Mass spectra of fl-C17H36 from the D20 11-C32H66 -NaOD system:
(a) alkane fraction and
(b) hydrogenated alkene fraction ................................................................
91
Gas chromatograms of the aliphatic fraction from the pyrolyses of
1,1 3-tetradecadiene, I -hexadecene and eicosane with D20 at 330°C:
(a) 1 hr;
(b) 5 hr;
(c) lOhr;
(d) 36 hr;
(e) 72 hr.
I.S. = internal standard (C24D50) ................................................................
92
3.14.
3.15.
Gas chromatograms of the hydrogenated aliphatic fraction from the
pyrolyses of 1,1 3-tetradecadiene, 1 -hexadecene and eicosane with D20
at 330°C:
(a) 1 hr;
(b) 5 hr;
(c) lOhr;
(d)36hr;
(e) 72 hr ....................................................................................................... 93
3.16.
Histograms showing the extent of deuterium substitution after pyrolysis in
D2Oforl hrat330°C:
(a) 1,1 3-tetradecadiene;
(b) 1 -hexadecane;
(c) eicosane .................................................................................................
3.17.
94
Histograms showing the extent of deuterium substitution after pyrolysis in
D2Ofor5hrat33O°C:
(a) 1,1 3-tetradecadiene;
(b) 1 -hexadecane;
(c) eicosane .................................................................................................
95
3.18.
Histograms showing the extent of deuterium substitution after pyrolysis in
D20 for 10 hr at 330°C:
(a) 1,1 3-tetradecadiene;
(b) 1 -hexadecane;
(c) eicosane ................................................................................................. 96
3.19.
Histograms showing the extent of deuterium substitution after pyrolysis in
D20 for 36 hr at 330°C
(a) 1,13-tetradecadiene;
(b) 1 -hexadecane;
(c) eicosane ................................................................................................. 97
3.20.
Histograms showing the extent of deutenum substitution after pyrolysis in
D20 for 72 hr at 330°C:
(a) 1,1 3-tetradecadiene;
(b) 1 -hexadecane;
(c) eicosane ............................................................................................... 98
3.21.
Gas chromatograms from the pyrolysis of LDPE in H20 for 72 hr @ 330°C:
(a) aliphatic fraction and
(b) hydrogenated aliphatic fraction.
Numbers refer to carbon chain lengths of 11-alkanes ................................ 99
3.22.
Mass fragmentogram mlz 99, representative of -a1kanes, for the
pyrolysis of the C14 polymer. Numbers refer to carbon chain
lengthsof -alkanes ...................................................................................
100
Overall average distribution of deuterium substitution in -a1kanes
from C17 to C29 generated from the D20 pyrolysis of Messel shale
(this research) ............................................................................................
101
Gas chromatograms of the aliphatic fraction from the pyrolyses of
1,1 3-tetradecadiene, I -hexadecene and eicosane spiked on Messel
shale in H20 at 330°C:
(a) 1 hr;
(b) 5 hr;
(c) lOhr;
(d) 36 hr;
(e) 72 hr.
I.S. = internal standard (C24D50) ..............................................................
102
Gas chromatograms of the hydrogenated aliphatic fraction from the
pyrolyses of 1,1 3-tetradecadiene, 1 -hexadecene and eicosane spiked
on Messel shale in H20 at 330°C:
(a) 1 hr;
(b) 5 hr;
(c) lOhr;
(d) 36 hr;
(e) 72 hr.
I.S. = internal standard (C24D50) ..............................................................
103
3.23.
3.24.
3.25.
3.26.
Gas chromatograms of the aliphatic fraction from the pyrolyses of
1,1 3-tetradecadiene, 1 -hexadecene and eicosane spiked on Messel
shale in D20 at 330°C:
(a) 1 hr;
(b) 5 hr;
(c) lOhr;
(d)36hr;
3.27.
3.28.
3.29.
3.30.
3.31.
3.32.
(e) 72 hr.
I.S. = internal standard (C24D50) ..............................................................
104
Gas chromatograms of the hydrogenated aliphatic fraction from the
pyrolyses of 1,1 3-tetradecadiene, 1-hex adecene and eicosane spiked
on Messel shale in D20 at 330 C:
(a) 1 hr;
(b) 5 hr;
(c) lOhr;
(d) 36 hr;
(e) 72 hr.
I.S. = internal standard (C24D50) ..............................................................
105
Histograms showing the extent of deuterium substitution after
pyrolysis on Messel shale in D20 for 1 hr at 330°C:
(a) 1,1 3-tetradecadiene;
(b) 1 -hexadecane;
(c) eicosane .................................................................................................
106
Histograms showing the extent of deuterium substitution after
pyrolysis on Messel shale in D20 for 5 hr at 330°C:
(a) 1,1 3-tetradecadiene;
(b) I -hexadecane;
(c) eicosane .................................................................................................
107
Histograms showing the extent of deuterium substitution after
pyrolysis on Messel shale in D20 for 10 hr at 330°C:
(a) 1,1 3-tetradecadiene;
(b) 1-hexadecane;
(c) eicosane .................................................................................................
108
Histograms showing the extent of deutenum substitution after
pyrolysis on Messel shale in D20 for 36 hr at 330°C:
(a) 1,1 3-tetradecadiene;
(b) l-hexadecane;
(c) eicosane .................................................................................................
109
Histograms showing the extent of deuterium substitution after
pyrolysis on Messel shale in D20 for 72 hr at 330°C:
(a) 1,1 3-tetradecadiene;
(b) 1-hexadecane;
(c) eicosane .................................................................................................
110
3.33.
Gas chromatograms for the pyrolysis products released from the Messel shale
kerogen during the pyrolyses in H20 at 330°C:
(a) 1 hr;
(b) 5 hr;
(c) lOhr;
(d) 36 hr;
(e) 72 hr.
Numbers refer to carbon chain lengths of -a1kanes. I.S. = internal
standard(-C32D66) ................................................................................... 111
3.34.
Gas chromatograms for the pyrolysis products released from the Messel shale
kerogen during the pyrolyses in H20 at 330°C:
(a) 1 hr;
(b) 5 hr;
(c) lOhr.
Same samples as in Fig. 3.33 but concentration increased to
show components in lower concentration. Numbers refer to carbon
chain lengths of -a1kanes. I.S. = internal standard (-C32D66) ................ 112
3.35.
Mass fragmentogram mlz 191 representing triterpenoid hydrocarbons
released from the Messel shale kerogen during the pyrolyses in H20 at
330°C:
(a) 1 hr;
(b) 5 hr;
(c) lOhr;
(d) 36 hr;
(e)72hr ....................................................................................................... 113
3.36.
Mass fragmentogram mlz 191 representing triterpenoid hydrocarbons
released from the Messel shale kerogen during the pyrolyses in D20
for72hrat33O°C ........................................................................................ 114
3.37.
Selected mass spectra of polydeuterated triterpenoid hydrocarbons
generated in the D20 pyrolysis of Messel shale for 72 hr at 330°C ............ 115
3.38.
Histograms showing the extent of deuterium substitution after
pyrolysis of molecular probes on Guaymas Basin sediment in D20
for lObr at 330°C:
(a) 1,1 3-tetradecadiene;
(b) 1 -hexadecane;
(c) eicosane .................................................................................................
116
Histograms showing the extent of deuterium substitution after
pyrolysis of molecular probes with 0.50 g elemental sulfur in D20
for 10 hr at 330°C:
(a) 1,1 3-tetradecadiene;
(b) I -hexadecane;
(c) eicosane .................................................................................................
117
3.39.
3.40.
3.41.
3.42.
Set of proposed reactions showing a simplified version of the major
primary and secondary reactions occurring during the pyrolysis of
n-C32H66 in H20 ........................................................................................
118
Set of proposed reactions showing a simplified version of the major
primary and secondary reactions occurring during the pyrolysis of
-C32H66 in D20 ........................................................................................
119
Set of proposed reactions showing a simplified version of the
deuterium exchange reactions occurring during the pyrolysis of
1,1 3-tetradecadiene in D20 ........................................................................
120
3.43.
Set of proposed reactions showing a simplified version of the
deuterium exchange reactions occurring during the pyrolysis of
1,13-tetradecadiene in D20 spiked on Guaymas Basin sediments ............. 121
3.44.
Set of proposed reactions showing a simplified version of the
thermal breakdown of LDPE under hydrous pyrolysis conditions .............
122
3.45.
Proposed reaction pathway for the thermal alteration and deuterium
exchange processes occurring during the D20 pyrolysis of Messel
shale ............................................................................................................. 123
4.1.
(a) Map of Gulf of California showing geographic location of the sampling
area, and
(b) Southern Trough of Guaymas Basin ..................................................... 136
4.2.
Gas chromatograms of volatile hydrocarbons:
a) 24 hr@ 200eC;
b) 24 hr @ 250°C;
c) 24 hr @ 300°C;
d)24hr@350°C ........................................................................................
4.3.
137
Gas chromatograms of the total extracts:
a) Unaltered;
b) 24 hr @ 200°C;
c)24hr@ 250°C;
d) 24 hr @ 300°C;
e) 24 hr @ 350°C.
Numbers refer to carbon chain lengths of -a1kanes ..................................
4.4.
138
Mass fragmentograms of mlz 99, characteristic of n-alkanes:
a) Unaltered;
b)24hr@ 200°C;
c) 24 hr @ 250°C;
d) 24 hr @ 300°C;
e)24hr@ 350°C.
Numbers refer to carbon chain lengths of -alkanes ..................................
139
4.5.
Mass fragmentograms of mlz 191, characteristic of triterpenoid
hydrocarbons:
a) Unaltered;
b)24hr@ 200°C;
c)24hr@ 250°C;
d)24hr@ 300°C;
e) 24 hr @ 350°C.
Concentrations of components are listed in Table 4.2................................
4.6.
140
Polycyclic aromatic hydrocarbon distributions for heating
experiments:
a) Unaltered;
b)24hr@ 200°C;
c)24hr@ 250°C;
d) 24hr@ 300°C;
e) 24 hr @ 350°C ........................................................................................
4.7.
141
Mass fragmentograms of two series of triaromatic steroid hydrocarbons
(m/z 217 and ni/z 231)
a) Unaltered;
b)24hr@ 200°C;
c)24hr@ 250°C;
d)24hr@ 300°C;
4.8.
4.9.
e) 24 hr @ 350°C.
Concentrations of Diels' hydrocarbon relative to polycyclic
aromatic hydrocarbons are shown in Fig. 4.6 .............................................
142
Mass fragmentogram (mlz 57, 58, 71, 72) representative of -ketones
present in the 350°C heating experiment ....................................................
143
Mass fragmentograms m/z 191 representative of triterpenoid
hydrocarbons:
a)PC-1,24hr@ 200°C;
b) PC-6, 392-397 cm below sea floor;
c) PC-i, 24 hr @ 350°C;
d) PC-6, 793-795 cm below sea floor.
Distributions for heating experiments and PC-6 showing parallel
transformations in the heating experiments and the naturally
alteredsediment ..........................................................................................
144
5.1.
Diagram showing expulsion of pyrolysates during conventional
hydrouspyrolysis ........................................................................................ 162
5.2.
Diagram showing the principle of confinement pyrolysis .......................... 163
5.3.
Lithologic column for DSDP Site 481A, location of samples for
pyrolysis are shown (Curray et al., 1982) ...................................................
164
5.4.
Representative mass fragmentograms mlz 191 for the triterpenoid
hydrocarbons in the extracts of sediment All- 112-29 PC 1:
a) Unaltered;
b) 24 hr @ 330°C;
c)48hr@ 330°C;
5.5.
5.5.
d)72hr@330°C ........................................................................................
165
Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment AII-112-29 PC-5:
a) 1 7a(H),2 1 (H)-29-hopane and 1 7(H),2 1 a(H)-29-hopane vs. time;
b) 17a(H),21 13(H)-30-hopane and i7(H),21a(H)-30-hopane vs. time ......
166
Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment All-i 12-29 PC-5:
c) I 7a(H),2 1 3(H)-3 1 -hopane (22S) and 1 73(H),2 I a(H)-3 1 -hopane(22R)
vs. time, and
d) 1 7a(H),2 1 (H)-32-hopane (22S) and I 7(H),2 I a(H)-32-hopane(22R)
vs. time ........................................................................................................ 167
5.6.
Representative mass fragmentograms (mlz 215, 217, 218, 257, 259) for
the steroid hydrocarbons in the extracts of sediment All- 112-29 PC 1:
a) Unaltered;
b) 24 hr @ 330°C;
c)48 hr@ 330°C;
d)72hr@330°C ......................................................................................... 168
5.7.
Histograms of the major aromatic compounds present in the extracts
of sediment All- 112-29 PC 1:
a) Unaltered;
b) 24 hr @ 330°C;
C) 48 hr@ 330°C;
d)72hr@330°C ........................................................................................
169
5.8.
Representative mass fragmentograms m/z 191 for the triterpenoid
hydrocarbons in the extracts of sediment 481A-8-7 (top):
a) Unaltered;
b) 24 hr @ 330°C;
C) 48 hr@ 330°C;
d)72hr@330°C ........................................................................................ 170
5.9.
Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment 481 A-8-7 (top):
a) I 7a(H),2 1 13(H)-29-hopane and 1 7(H),2 I a(H)-29-hopane vs. time;
b) 1 7a(H),2 1 (H)-30-hopane and I 7(H),2 I a(H)-30-hopane vs. time
5.9.
171
Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment 481 A-8-7 (top):
c) 1 7a(H),2 1 (H)-3 1 -hopane (22S) and I 7(H),2 1 a(H)-3 1 -hopane(22R)
vs. time;
d) 1 7a(H),2 1 3(H)-32-hopane (22S) and 1 7(H),2 1 a(H)-32-hopane(22R)
vs. time ........................................................................................................ 172
5.10.
5.11.
Representative mass fragmentograms (miz 215, 217, 218, 257, 259) for
the steroid hydrocarbons in the extracts of sediment 481 A-8-7 (top):
a) Unaltered;
b) 24 hr @ 330°C;
C) 48 hr@ 330°C;
d)72hr@330°C ........................................................................................
173
Histograms of the major aromatic compounds present in the extracts
of sediment 481 A-8-7 (top):
a) Unaltered;
b)24hr@ 330°C;
5.12.
c) 48 hr @ 330°C;
d)72hr@330°C ........................................................................................
174
Representative mass fragmentograms mlz 191 for the triterpenoid
hydrocarbons in the extracts of sediment 481 A-22-7 (top):
a) Unaltered;
b) 24 hr @ 330°C;
c) 48 hr@ 330°C;
d)72hr@330°C ........................................................................................
175
5.13.
Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment 481A-22-7 (top):
a) I 7a(H),2 1 f3(H)-29-hopane and 1 7(H),2 1 a(H)-29-hopane vs. time;
b) 1 7a(H),2 1 (H)-30-hopane and 1 713(H),2 I a(H)-30-hopane vs. time ....... 176
5.13.
Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment 481A-22-7 (top):
c) I 7a(H),2 1 (H)-3 1 -hopane (22S) and 1 73(H),2 1 a(H)-3 1 -hopane(22R)
vs. time;
d) 1 7a(H),2 1 (H)-32-hopane (22S) and 1 7(H),2 1 a(H)-32-hopane(22R)
vs. time ........................................................................................................ 177
5.14.
Representative mass fragmentograms (mlz 215, 217, 218, 257, 259) for
the steroid hydrocarbons in the extracts of sediment 481 A-22-7 (top):
a) Unaltered;
b) 24 hr @ 330°C;
c)48hr@ 330°C;
d)72hr@330°C ........................................................................................ 178
5.15.
Histograms of the major aromatic compounds present in the extracts
of sediment 481 A-22-7 (top):
a) Unaltered;
b) 24 hr @ 330°C;
c)48hr@ 330°C;
d)72hr@'330°C ........................................................................................
5.16.
179
Plot showing the yields of Diels' hydrocarbon in the heating
experiments for the three sediment samples ............................................... 180
6.1.
Portion of a gas chromatogram showing the elution order of six
C4 ketone isomers ...................................................................................... 189
6.2.
Mass spectra of standard aliphatic ketone standards:
a) Tetradecan-2-one;
b) Tetradecan-3-one;
c) Tetradecan-4-one;
d) Tetradecan-5-one;
e) Tetradecan-6-one;
f) Tetradecan-7-one ..................................................................................... 190
6.3.
Mass spectra corresponding to the peaks in Fig. 6.1 ...................................
6.4.
Gas chromatograms of the hydrothermal oil 1972-CHI Interior:
a) polar NSO fraction and
b) isolated ketone fraction of the NSO fraction .......................................... 192
6.5.
Gas chromatograms of the H20 -C32H66 Sulfide system
(72 hr @ 350°C):
a) nonpolar aliphatic fraction and
b) polar NSO fraction .................................................................................
6.6.
191
193
Gas chromatograms of the polar NSO fractions obtained by hydrous
pyrolysis of 1,1 3-tetradecadiene, I -hexadecene and eicosane on
Messel shale:
a) 1 hr@ 330°C;
b) 5 hr @ 330°C;
c) lOhr@ 330°C;
6.7.
6.8.
6.9.
d) 36 hr @ 330°C;
e) 72 hr @ 330°C. Internal standards: n-C24D50 and n-C32D66 ..............
194
Reconstructed ion chromatograms (RIC) representative of the
aliphatic ketones generated during the molecular probe experiments
pyrolyzed with Messel shale:
a) ketones from 1,1 3-tetradecadiene;
b) ketones from 1 -hexadecene;
c) ketones from eicosane ............................................................................
195
Mass fragmentogram (mlz 57, 58, 71; 72) representative of the aliphatic
ketones present in a hydrothermally-derived oil (1972-CH1 Interior) .......
196
Proposed reaction scheme for the generation of ketones during the
pyrolysis of aliphatic-rich organic matter ................................................... 197
LIST OF TABLES
Table
Page
2.1.
Location of oil covered hydrothermal vent samples ..................................
23
2.2a.
Sample summary for DSDP Site 477 .........................................................
24
2.2b.
Sample summary for DSDP Site 481A ......................................................
25
2.3.
Bulk characterization of seabed chimney oils ............................................
26
2.4.
Summary of molecular parameters for hydrothermal vent oils .................. 27
2.5.
Selected parameters for the aliphatic fractions of DSDP Leg 64
Hole481A ................................................................................................... 28
3.1.
Hydrous pyrolysis experiments performed at 330°C .................................
75
3.2.
Extent of deuterium substitution in normal hydrocarbons produced from
the pyrolysis of Messel shale at 330°C for 72 hr with D20 .......................
76
3.3.
Data from the pyrolysis of 1,1 3-tetradecadiene and 1 -hexadecene
molecular probes with Messel in H20 at 330°C ......................................... 77
3.4.
Data from the pyrolysis of 1,1 3-tetradecadiene and 1 -hexadecene
molecular probes with Messel in D20 at 330°C........................................
78
Analytical results of volatile hydrocarbon analyses for 24 hr
heating experiments ....................................................................................
134
Triterpenoid concentrations from the 24 hr heating experiments
(ng/g sed.) ...................................................................................................
135
5.1.
Selected parameters for the aliphatic fractions of All-i 12-29 PC-5 ..........
159
5.2.
Selected parameters for the aliphatic fractions of 481A-8-7
(top of pipe) ................................................................................................. 160
5.3.
Selected parameters for the aliphatic fractions of 481A-22-7
(top of pipe) ................................................................................................. 161
4.1.
4.2.
LABORATORY SIMULATED HYDROTHERMAL ALTERATION OF
SEDIMENTARY ORGANIC MATTER FROM GUAYMAS BASIN, GULF OF
CALIFORNIA
CHAPTER 1
Introduction
The process of convective cooling of ridge-crest systems, known as seafloor
hydrothermal circulation, was first proposed by Anderson and co-workers (1977) to
explain the deficiency of conductive heat loss observed at ridge axes in the Indian
Ocean. It was also in 1977 that the first observations were made of seafloor
hydrothermal venting at the Galapagos spreading center (Corliss et al., 1979). The
phenomenon of hydrothermal venting at seafloor spreading centers is now considered
a widespread and common process (Von Damm, 1990 and references therein).
Hydrothermal systems can be broadly classified as sedimented or
unsedimented. Fig. 1.1 shows the hydrothermal systems of the Eastern Pacific. Of
the hydrothermal areas documented so far on this tectonic system, Middle Valley,
Escanaba Trough and Guaymas Basin are classified as sedimented rift systems, with
the Guaymas Basin being the most thoroughly studied active, sediment-covered
hydrothermal vent system.
Guaymas Basin is the largest of the enclosed basins in the Gulf of California
with dimensions of approximately 240 x 60 km (Fig. 1.2). The two deepest areas are
the parallel spreading centers which are 3 to 5 km wide and approximately 100 m
deeper than the sunounding sea floor. These are the northern and southern axial rift
valleys (40 and 20 km long, respectively) that overlap at a non-transform offset
(Lonsdale and Becker, 1985).
The high sedimentation rate of 1 to 4 m I kyr (van Andel, 1964; Calvert, 1966;
Curray et al., 1982) is much higher than typical pelagic rates over other spreading
centers. The diatomaceous nanofossil ooze from the plankton blooms (Calvert, 1966)
and clastic rich turbidites that pour into the two troughs fill the basin with a sediment
cover (Einsele and Kelts, 1982) estimated at 500 m thick (Lonsdale and Lawyer,
2
1980). The reducing conditions in the sediments and low bottom water oxygen
concentrations contribute to a total organic carbon content of 3 to 4% (Goidhaber,
1974). Fig. 1.3 is a schematic of the hydrothermal convection of seawater through the
sediment cover.
The thick sediment cover prevents extrusion of fresh basalt onto the seafloor.
Instead the newly accreted material solidifies as intrusions intercalated within the
sediments (Moore, 1973; Williams et al., 1979; Einsele et al., 1980; Gieskes et al.,
1 982a,b). The results of this process are shown schematically in Fig. 1.4. Two
distinct types of hydrothermal systems are operating in Guaymas Basin (Kastner,
1982). A minor system consists of intrusions of hot sills into the highly porous cold
sediments (150-200°C), and a major hydrothermal circulation system consists of a
relatively shallow magma chamber driving large scale circulation (300±50°C). Both
of these processes heat and pyrolyze the sedimentary organic matter to produce
petroleum (Simoneit and Lonsdale, 1982). This process of hydrothermal petroleum
generation has been documented at other sedimented rift systems (Kvenvolden et al.,
1986, 1988; Kvenvolden and Simoneit, 1990; Simoneit et aL, 1992; Simoneit, 1990,
1993).
The hydrothermal fluids of the Guaymas Basin hydrothermal system transport
large amounts of hydrocarbons to the seafloor, primarily of thermogenic origin
(Simoneit and Lonsdale, 1982; Simoneit, 1985). Previous analyses have shown that
there is a large variation in the character of the hydrothermal oils. These oils can
differ in the amounts of saturated, branched, aromatic and polar components present
(Simoneit and Lonsdale, 1982; Kawka, 1990). But in general, the oils formed by this
hydrothermal alteration of sedimentary organic matter are characteristically more
polar, with a relatively high proportion of aromatic components (Simoneit, 1984;
Kawka and Simoneit, 1990).
This study was a continuation of the research into hydrothermal petroleum
generation at the Guaymas Basin hydrothermal system. It was conducted to elucidate
some of the chemical pathways that control the distributions of the major compounds
present in oils from the Guaymas Basin hydrothermal system. This research involved
an extension of the survey of oils and sediment extracts to include the polar nitrogen,
sulfur and oxygen-containing (NSO) fraction, identifying the major resolved
compounds in this fraction. In addition to the survey, laboratory heating experiments
by closed system pyrolysis on Guaymas Basin sediments were conducted, and the
changes in the content of the solvent extractable organic matter that is resolvable by
3
gas chromatography was monitored. Specifically, two primary objectives were
pursued:
(1) perform a survey of the poiar (NSO) fraction of hydrothermally derived
oils from Guaymas Basin and identify the major oxygen-containing
compounds; and
(2) duplicate some key aspects of oil generation by hydrothermal processes
using laboratory hydrous pyrolysis.
This research is motivated by the need to understand the factors that control
the transformation of sedimentary organic matter to petroleum. A more complete
characterization of the oils and sediment extracts, combined with laboratory pyrolysis
studies, should aid in elucidating some of the major chemical pathways by which
contemporary organic matter is transformed into oil. An understanding of high
temperature pyrolytic conversion is a prerequisite to continued research on this system
or other sedimented ridge systems, where different sources of organic matter and
inorganic mineral assemblages could influence the pyrolysis products. How the study
outlined above relates to hydrothermal conversion of marine sedimentary organic
matter conversion is discussed below.
Survey of hydrothermal oils and sediment extracts from the Guaymas Basin
hydrothermal system. The previous investigations into the compositions of
hydrothermal petroleum have also involved the search for organic compounds that are
characteristic of a hydrothermal mode of formation, and could therefore be used as
indicators of the quick, high temperature mode of organic matter maturation.
Correlations have been made between the high thermal stresses encountered in the
Guaymas Basin hydrothermal system and Dielst hydrocarbon (1,2-(3'methylcyclopenteno)phenanthrene), a triaromatic steroid hydrocarbon common in
Guaymas Basin oils. This compound has been used as an indicator of rapid
hydrothermal petroleum generation processes (Kawka, 1990; Simoneit et al., 1992),
although downcore investigations of sediments thermally altered by contact
metamorphism from sill intrusions have found lower amounts in these areas than what
is expected from the analyses of seabed oils (Kawka, 1990). These previous
investigations have focused primarily on the aliphatic and aromatic components, with
ri
only cursory mention of some poiar components of the hydrothermal oils (Gieskes et
al., 1988).
As the next step in characterizing petroleum generated by hydrothermal
processes, a survey was undertaken of the GC resolved components of the polar NSO
fractions in oils and thermally-altered sediment extracts. This survey identified some
major oxygenated compounds that appear to be uniquely associated with a high
temperature hydrothermal mode of formation. The analyses of the poiar NSO
fractions were correlated to the aliphatic and aromatic fractions. A description of the
samples used in the survey and a summary of the results are presented in Chapter 2.
A complete display of the gas chromatograms from this survey is presented in
Appendices 1 3.
Simulated hydrothermal alteration of sedimentary organic matter by laboratory
hydrous pyrolysis. Extensive laboratory research has been performed to further our
understanding of the chemical transformations which occur during the maturation of
sedimentary organic matter. In simulating the natural oil generation process, high
temperature experiments are performed to compensate for the lower temperatures and
longer durations during natural petroleum generation. The procedure of laboratory
hydrous pyrolysis is one method used to study the transformations of sedimentary
organic matter. This procedure is defined as the pyrolysis of a sample in contact with
liquid water (Lewan et al., 1979), with the water I sediment ratio adjusted to insure
that the sample is completely submerged in the liquid phase at the reaction
temperature (Lewan, 1992). Hydrous pyrolysis is commonly used to further our
understanding of the oil generation process by assessing the maturation level of
petroleum and sedimentary organic matter after different time I temperature intervals
(Lewan, 1993 and references therein).
Hydrous pyrolysis is well suited for simulating hydrothermal processes since
hydrothermal oils are the result of natural hydrous pyrolysis occurring at high
temperature over a relatively short time (Simoneit, 1992). A detailed investigation
was undertaken to study the major reactions occurring under simulated hydrothermal
conditions using pure organic compounds and an organic-rich shale. The results are
presented in Chapter 3. By combining these results with the knowledge of the actual
organic chemical reactions which occur on mineral surfaces (Solomon, 1968; Wilson
et al., 1986; Regtop et al., 1985; Kissin, 1987; Weres et al., 1988; Lao et al., 1989;
Smith et al., 1989) and under high temperature aqueous conditions (Blouri et al., 1981;
Breslow, 1991; Depeyre and Flicoteaux, 1991; Siskin and Katritzky, 1991 and
5
references therein), a more detailed model of organic conversions under hydrous
pyrolysis conditions was developed.
A series of hydrous pyrolysis experiments was performed on a surface
sediment from Guaymas Basin. The effects of temperature on the nature and
concentrations of selected components in the pyrolysates were documented. The
results of this study are presented in Chapter 4.
A modified pyrolysis technique was developed which was better suited
towards simulating the natural conditions during hydrothermal alteration of
sedimentary organic matter. Using this method, three Guaymas Basin sediment
samples which have undergone different amounts of diagenesis were pyrolyzed.
These heating experiments were compared to downcore sediment sequences that have
been thermally altered by a sill intrusion. The results are presented in Chapter 5.
Aliphatic ketones are highly correlated with high temperature pyrolysis
conditions, both natural and simulated. In addition to some selected results from the
previous pyrolysis experiments, the results from additional heating experiments are
summarized in Chapter 6. Simulation of the natural hydrothermal pyrolysis process
by laboratory hydrous pyrolysis techniques provides information regarding the mode
of alkanone formation.
A summary of the overall results is presented in Chapter 7. The insight gained
from the study of laboratory methods for simulating hydrothermal oil generation has
better defined the experimental design and conditions necessary which best suit the
simulation processes, and application of these results to the natural hydrous pyrolyses
broaden our understanding of the conditions which control the formation of oil by
high temperature hydrothermal processes.
The reader of this thesis should be aware that the chapters of this thesis are
written in manuscript format to facilitate submission of the chapters for publication.
As such, there is unavoidably some duplication of material from chapter to chapter.
MEDDLE VALLEY
SOUTHERN JUAN di FUCA
ESCANABA TROUGH
GUAYUAS BASfl4
(
\)
21°NEPR
13°N EPH u
GALAPAGOS
'9
Figure 1.1. Map of discovered submarine hydrothermal systems of the Eastern Pacific
(Von Damm, 1991).
t15°
3Q0
23°
tO 5°
Figure 1.2. Map of the Guaymas Basin hydrothermal system, Gulf of California
(Gieskes et al., 1991).
SEAWATER
GUAYMAS HYDROTHERMAL
FLUID DISCHARGE
COLD (3°C)
pH-8
TEMP. VAR., MAX. 315°C
OXIDIZING
pH-6
S0
REDUCING
RICH
METAL DEFICIENT
(eg. Fe 002 ppm
Mn 0.01 ppm
Zn O.005ppm
Cu O.Olppm)
MgRICH(I272ppm)
2000rn
H2S RICH
METALS 2-20% LESS
THAN END-MEMBER
NO Mg
. HYDROCARBONS, C1-C4
4
4
SEDIMENTS IN RIFT
\
WATER-ROCK
REACTION
300-500m
STOCKWORK ZONE IN
LOWER SEDIMENTS/ROCK
-
N(RECHARGE)
2000
HYDROTHERMAL FLUID
(END-MEMBER)
HOT (350°C)
pH-4
H2S RICH
REDUCING
AD.4PTED FROM
SCOTT (/983)
METAL RICH
(eg. Fe IOOppm
Mn 33 ppm
Zn
7ppm
Cu
2ppml
'NO Mg
Figure 1.3. Diagram showing the hydrothermal convection of seawater in a sedimentcovered spreading center (adapted from Scott, 1983; Simoneit, 1985).
9
_/ 7
UI
11
pL.4
---- _/7 t_)
_-q -,
,
.-
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t
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4tL.4.4141
____._.-.__._._._______x__._.___L,
1\1
tkt1
'
'
4.
'-.__
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tL>
i':"
\
11
-\
.3
'.4
r:I '-._L.
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c7m
1'Zi------I 1'
wv.
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I
7*
W
<,.La 7
dC
, < <
t'
qt
V
&,, C't
t7C.j'g <Vc< C
V1ttt.
, c.;:
'4.A
a1
p.A"f..tt3'A 4.4 t4
t'-4
r
'V
LA
Figure 1.4. Schematic version of hydrothermal systems in Guaymas Basin , Gulf of
California. C = cold water advected down through fault zones. H = hot water
advected through sediments and fault zones (Adapted from Gieskes et al., 1982b).
CHAPTER 2
Survey of the Polar (NSO) Fractions of Seabed Oils and Sediment Extracts
11
ABSTRACT
The aliphatic, aromatic and poiar (NSO) fractions of seabed oils and sediment
extracts from the Guaymas Basin hydrothermal system have been analyzed by gas
chromatography and gas chromatography
mass spectrometry. The oils were
collected from the interiors and exteriors of high temperature hydrothermal vents and
represent hydrothermal pyrolysates that have migrated to the seafloor by hydrothermal
fluid circulation. The downcore sediments are representative of both thermally
unaltered and thermally altered sediments. The survey has revealed the presence of
oxygenated compounds correlated with samples exhibiting a high degree of thermal
maturity. Several homologous series of related ketone isomers are enriched in the
interiors of the hydrothermal vent samples or in hydrothermally-altered sequences of
the downcore sediments The ketones range in carbon number from C11 to C31 with a
Cmax from C15 to C23, distributions that are similar to those of the n-alkanes. The
alkan-2-ones are usually in highest concentrations, with lower amounts of 3-, 4-, 5-,
6-, 7- (and higher) homologues. The alkanones possess no carbon number preference.
A second class of oxygenated compounds found in these same samples are the
phenols. A series of methyl-, dimethyl- and trimethyl-isoprenoid phenols are present
in all of the seabed NSO fractions, with the methyl- and dimethyl-isoprenoid phenols
present as major components, and a trimethyl-isoprenoid phenol as a minor
component. A homologous series of ll-alkylphenols have also been found in the
seabed oils. The alkanones and phenols are derived from the hydrothermal alteration
of sedimentary organic matter. The ketones and n.-alkylphenols are most likely
synthesized under hydrothermal conditions, but the isoprenoid phenols are probably
hydrothermal alteration products of natural product precursors. The suite of normal
ketones should be useful tracers of high temperature hydrothermal processes.
12
INTRODUCTION
Hydrothermal activity is common at tectonic spreading ridges throughout the
world. The Guaymas Basin, Gulf of California is a spreading center under a thick
cover of diatomaceous oozes and mud turbidites. The combination of plate accretion
by dike and sill intrusions into the sediments and accompanying high temperature
hydrothermal fluids pyrolyze the sedimentary organic matter to produce petroleum.
The petroleum can be transported to the seafloor by hydrothermal fluid migration.
14C ages for selected petroleum samples range from 4240 to 5705 years B. P.
indicating that a significant proportion of the hydrothermal petroleum is derived from
Recent organic detritus (Peter et al., 1991). Hydrothermal petroleum derived from
shallow sediments are characteristically enriched in polar constituents and have a high
polycyclic aromatic hydrocarbon content (Simoneit, 1983, 1984; Kawka and
Simoneit; 1990). Guaymas Basin is the most thoroughly studied sediment-covered
spreading center. Although extensive research has been performed on the
characterization of the aliphatic and aromatic fractions of these hydrothermal oils
(Simoneit and Lonsdale, 1982; Simoneit, 1985, 1990), little is known about the polar
nitrogen, sulfur and oxygen (NSO) fraction.
This chapter is an organic geochemical survey of the NSO fractions of
representative oils and sediment extracts from the Guaymas Basin hydrothermal
system. Comparisons are made to the aliphatic and aromatic fractions of the oils and
sediment extracts. Specifically, two types of samples were studied : (1) seabed oils
associated with high temperature seafloor hydrothermal vents that have been migrated
with the hydrothermal fluids and condensed in the vent spires; and (2) extractable
organic matter in downcore sediments representative of unaltered and hydrothermally
altered regions. The objective of this research is to characterize some of the
components in one of the major fractions of the oils, the polar (NSO) fraction.
13
EXPERIMENTAL
Samples. The seabed oils for this study were sampled from the interiors and
exteriors of hydrothermal vents collected during the dives of the Deep Submergence
Vessel (D.S.V.) Alvin in March, 1988. Figure 2.1 is a location map of the Guaymas
Basin hydrothermal system located in the Gulf of California. Figure 2.2 is a detailed
bathymetric chart of Guaymas Basin showing the general locations of Alvin dives
1981-1984. The transponder array with its x,y coordinates is also indicated (Simoneit,
1988). The x,y coordinates of the oil covered hydrothermal vents are listed in Table
2.1.
The subsurface sediment samples analyzed in this study were collected during
Leg 64 of the Deep Sea Drilling Project (DSDP) from December, 1978 to January,
1979.
The selected downcore samples were taken from Holes 477 and 481A.
Locations of the two drill sites are shown in Figure 2.1. The lithologic columns for
Sites 477 and 481A are shown in Figure 2.3. The sample listings, depths and
descriptions are summarized in Table 2.2.
Extraction and fractionation. The frozen hydrothermal vent samples were
brought to room temperature and oil samples were collected from the interiors and
exteriors of each specimen. They were diluted in chloroform and filtered to remove
any debris and passed through an activated copper column to remove the elemental
sulfur. The samples were reduced to 2 mL by rotary evaporation.
The DSDP samples have been freeze dried and stored at room temperature
until analysis. Powdered sediments ranging in size from 10 to 40 g were extracted for
72 hours with methanol / methylene chloride in a Soxhiet extractor. The extract was
combined with 100 mL water and the aqueous phase acidified with 6N HC1. The
organic phase was collected and the aqueous phase was extracted with two 50 mL
portions of methylene chloride. The three organic extracts were combined and solvent
removed to near dryness by rotary evaporation.
The whole oils and sediment extracts were deasphalted with 100 mL heptane.
The asphaltenes were allowed to precipitate for 24 hrs and removed by filtration. The
deasphalted fractions were reduced to 4 mL and fractionated by column
chromatography (30 cm x 1 cm) packed with 3.8 g alumina (fully active) over 3.8 g
silica gel (fully active). The samples were separated into three fractions by elution
with 50 mL heptane (aliphatic, Fl), 50 mL toluene (aromatic, F2) and 25 mL
methanol (polar NSO, F3).
14
Quantitation was by the addition of fl-C24D50 for aliphatic fractions and D10pyrene for aromatic and poiar fractions.
Gas chromatography. Gas chromatography (GC) of the oil fractions was
performed with a Hewlett Packard 5890A equipped with a 30 m x 0.25 mm i.d. DB-5
open tubular column (0.25 pm film thickness). The GC oven was heated using the
following program: isothermal for 2 mm. at 65°C, 4°/mm. to 310°C, and isothermal
for 30 mm., with the injector at 290°C, detector at 325°C, and helium as the carrier
gas.
Gas chromatography-mass spectrometry. The gas chromatography-mass
spectrometry (GC-MS) was performed on a Finnigan 9610 gas chromatograph
coupled to a Finnigan 4021 quadrupole mass spectrometer operated at 70 eV over the
mass range 50-650 dalton and a cycle time of 2.0 s. The GC oven temperature was
programmed at isothermal for 2 mm. at 65°C, 3°/mm. to 3 10°C, and isothermal for 30
mm., with the injector at 290°C, and helium as the carrier gas. The MS data were
processed with an on-line Finnigan-Incos 2300 computer data system.
15
RESULTS AND DISCUSSION
Seabed oils. The results of the bulk chromatographic separations into the
compound classes for the four hydrothermal vent samples are listed in Table 2.3 and
shown in Fig. 2.4 (a-d) . Samples 1972-CH1, 1983-CH1 and 1984-CH1 show a
consistent difference between their interior and exterior oils. The exterior oils all
show a decrease in the proportion of the aliphatic fractions with an accompanying
increase in the aromatic, polar and asphaltene fractions relative to the interior oils.
The interior and exterior samples from 1984-CH2 have essentially the same
proportions of the four fractions. These compositional differences between the
interior and exterior oils are more clearly shown in Fig. 2.5 which is a ternary diagram
of the gross oil compositions where the NSO and asphaltene fractions have been
combined into one compound class. Included on the ternary diagram are seabed oil
samples from Guaymas Basin collected during previous Alvin dives and dredge
sampling expeditions (Kawka and Simoneit, 1987).
The variations in the distribution of the oils from the interiors and the exteriors
of the high temperature hydrothermal vents reflect the process of biodegradation
occurring after migration to the seafloor (Kawka and Simoneit, 1987). With the
exception of oil 1984-CH2, whose interior and exterior oils are almost identical in
composition, the seabed oils have a significant decrease in the aliphatic portion of the
bulk composition. Water washing, the removal of water-soluble components, is
another likely factor working in combination with biodegradation to alter the bulk
compositions of the oils and thus enrich the NSO fractions (Tissot and Welte, 1984).
The aliphatic, aromatic and polar NSO fractions of the eight seabed oils have
been analyzed by gas chromatography. The complete set of gas chromatograms are
located in Appendix 1. The hydrothermal oils from 1972-CH1 were selected as
representative oils for discussing the major characteristics of the seabed samples. The
gas chromatograms of the aliphatic, aromatic and NSO fractions from the
hydrothermal oils of 1972-CH1 are presented in Fig. 2.6 and 2.7.
The hydrocarbon patterns of the aliphatic fractions are typical of other normal
hydrothermal seabed oils previously reported (Simoneit, 1984).
The aliphatic
fractions of these oils have smooth -a1kane distributions (carbon preference index,
CPI = 1) with the other major components being the isoprenoids, with the isoprenoids
pristane and phytane in highest concentrations. The -alkanes range in carbon number
from 11 to 25, with the l984-CH1 oils containing hydrocarbons up to C29. The
16
pristane /phytane ratios range from 1.1 to 1.7. However, there is a consistent trend of
the exterior oils having a decreased amount of normal hydrocarbons relative to the
isoprenoid hydrocarbons, characteristic of having undergone slight biodegradation
relative to the corresponding oil from the interior of the vent. This is most pronounced
in the oils from 1972-CH1 (Fig. 2.6a and 2.7a), where the pristane/n-C17 and
phytane/n-C 8 ratios of the exterior oil are 4.25 and 3.31 respectively, but the
and phytane/p-C 8 ratios of the interior oil are 0.79 and 0.51
pristane/n-C
respectively. The molecular parameters for these oils are summarized in Table 2.4. In
slightly and moderately biodegraded oils, the
-alkanes are the first class of
compounds to be removed, leaving the isoprenoid hydrocarbons relatively unaffected
(Connan et al., 1980; Tissot and Welte, 1984). Although the -alkanes are present in
all oils, there is a significant increase in the Pr/-C17 and Pr/n-C18, characteristic of
the very early stages of biodegradation.
The aromatic fractions contain polycyclic aromatic hydrocarbons and alkylated
polycyclic aromatic hydrocarbons common to other Guaymas Basin seabed oils
(Simoneit and Lonsdale, 1982, Kawka and Simoneit, 1990). The GC traces of the
aromatic fractions are characterized by a large unresolved complex mixture (UCM)
which results in a large hump in the chromatogram, with the resolved components on
this hump. Except for the oils from 1 984-CH2, where the interior and exterior oils are
very similar, the resolved component in highest concentrations in most of the aromatic
fractions from the chimney exteriors is Diels' hydrocarbon (1,2(3t
methylcyclopenteno)phenanthrene), a triaromatic steroid hydrocarbon common in
Guaymas Basin oils and an indicator of rapid hydrothermal petroleum generation
processes (Kawka, 1990; Simoneit et al., 1992a). Diels' hydrocarbon (DHC) and
some of the other major resolved polycyclic aromatic hydrocarbons (PAll) are
identified in the aromatic fractions of the 1972-CH1 oils (Fig. 2.6 and 2.7).
The polar NSO fractions, similar to the aromatic fractions, are dominated by a
large UCM, with the resolved components on this hump. Two classes of homologous
oxygenated compounds, alkanones and phenols, have been identified as the major
resolved components of the NSO fractions.
The alkanones occur as several homologous series which range in carbon
number from C11 to C31 with a Cmax from C15 to C23. These oils contain alkan-2ones in highest concentrations, with lower amounts of 3-, 4-, 5-, 6-, 7- (and higher)
alkanones. These compounds possess no carbon number preference and are enriched
in the interiors of the hydrothermal vent spires indicating the ketones have a pyrolytic
17
origin at depth or are formed by reaction with the hot hydrothermal fluids, and do not
originate from an external biogenic deposition. The relative decrease of the aliphatic
ketones of the poiar fractions of the exterior oils is likely due to preferential microbial
utilization of straight-chain aliphatic components. Fig. 2.8 shows the distribution of
ketones present in a representative oil, the interior oil from vent 1 972-CH1.
The second class of oxygenated compounds are the phenols. A series of
methyl-, dimethyl- and trimethyl-isoprenoid phenols were present in all of the NSO
fractions, with the methyl- and dimethyl-isoprenoid phenols present as major
components, and a trimethyl-isoprenoid phenol as a minor component. The tentative
structure assignments were made by interpretation of the mass spectra of the parents
and silylated derivatives and by the similarities to the mass spectra of the mono-, di-
and trimethylchromans (Sinninghe Damsté et al., 1987), structurally related
compounds possessing an isoprenoid side chain. The two compounds in highest
concentration exhibited characteristic mass spectra with ions at m!z 107, 122, 135, 161
and 388 (molecular ion, M) and m/z 121, 136, 149 and 402 (M). These compounds
are labeled A and B in Fig. 2.6 - 2.7. A third phenol, compound C, is found in trace
levels and has a characteristic mass spectrum of m/z 135, 150, 194, 374 and 416 (M).
Fig. 2.9 shows the mass fragmentograms of the characteristic ions of these
compounds. The mass spectra of compounds A, B and C, and the proposed structures
are shown in Fig. 2.10, which were present in interior oil of chimney 1972-CH1 F3, a
representative oil sample. Treating this oil with a silylating agent (BSTFA, Pierce
Chemical Co.) produced the trimethylsilane derivatives of compounds A, B and C
(labeled A', B' and C') with characteristic ions of 179, 194, 207 and 460 (M), 193,
208, 221 and 474 (Mt) and 193, 222, 266 and 488 (Mt), respectively. The mass
fragmentograms of the characteristic ions of these three derivatives are shown in Fig.
2.11, and mass spectra of the three derivatized phenols are shown in Fig. 2.12.
Present in much lower concentrations are homologous series of n-alkylphenols.
These series are shown in Fig. 2.13. Representative mass fragmentograms of the C27
to C29 -a1kylphenols is shown in Fig. 2.14, and mass spectra are shown in Fig. 2.15.
Downcore sediment extracts from DSDP Site 477. Site 477 is located in the
southern rift of Guaymas Basin. A total of 191 meters was cored. A massive dolerite
sill was encountered between 58 and 105.5 m below seafloor (mbsf). The sediments
above the sill consist primarily of olive-brown hemipelagic diatom oozes and mud
turbidites. Extensive hydrothermal alteration of the sediments has occurred below the
sill resulting in grey claystones and sandstones, with dolomite, pyrite and quartz
iI:
(Curray et al.,
Three sediment samples above the sill and twelve sediment
samples below the sill were extracted and analyzed by GC. A few samples were
selected for analysis by GC-MS. The complete set of the gas chromatograms for the
total cxtracts and the aliphatic, aromatic and NSO fractions are located in Appendix 2.
An extensive analysis of the aliphatic and aromatic fractions of sediments altered by
the emplacement of the dolorite sill has previously been reported (Kawka, 1990).
Therefore, only a brief discussion of some representative samples will be presented.
Sample 477-2-2 (145-150) is representative of a typical near-surface sediment,
dominated by long-chain -a1kanes with a CPI=3.9, characteristic of a terrigenous
source for these n-alkanes (Brassell et al., 1978). The major aromatic component is
perylene, a diagenetically-derived PAH (Louda and Baker, 1974). Both sample 4777-1 (88-90) and 477-7-1 (106-108) resemble other samples from Guaymas Basin that
have undergone thermally-enhanced diagenesis (Simoneit et al., 1984, 1992b), where
the total extract is dominated by pristane, phytane, the C25 isoprenoid thiophenes and
the steroid biomarkers. The polar fractions of both samples contain a large UCM with
few resolved components. Two samples near the sill contact zone, 477-16-2 (140145) and 477-16-2 (145-150), are fully mature organic extracts. The CPI=1 for the
alkanes and the aromatic fractions contain the full suite of PAH and alkylated-PAH.
Of interest is the presence of the alkyl ketones. The alkanones occur as several
homologous series which range in carbon number from C11 to C33. As with the
seabed oils, these sediment extracts contain 2-, 3-, 4-, 5-, 6-, 7- (and higher) alkanones.
There is no carbon number preference and their correlation with the oil zone suggests
that the ketones have a high temperature pyrolytic origin. Deeper in the sediment
column the alteration is extensive, resulting in low yields in the extractable organic
matter from the sediments. The total extracts are dominated by the aromatic
components. The ketones are not present or are in lower concentrations in these
sediments. It is interesting to note that samples 477-16-4 (135-140) and 477-17-1
(145-150) have a bimodal n-alkane distribution with maxima at C10 and
C23.
The low
molecular weight component is from a condensate and contains the diamondoid
hydrocarbons adamantane, diadamantane, triadamantane and their alkylated
derivatives, analogous to petroleum condensates (Wingert, 1992). This portion of the
sediment column was apparently an active flow channel for the condensate.
Downcore sediment extracts from DSDP Site 481 A. Site 481 A is located in
the northern rift of Guaymas Basin. A total of 384 meters was cored. A massive chert
and dolerite sill complex was encountered between 169.5 and 200 mbsf. The
19
sediments above the sill consist primarily of olive-brown diatomaceous muds with
intercalations of grey, muddy sands (Curray et al., 1982). Hydrothermal alteration of
the sediments has occurred in contact zones above and below the sill. Seven sediment
samples above the sill and nine sediment samples below the sill were extracted and
analyzed by GC. The complete set of the gas chromatograms for the total extracts and
the aliphatic, aromatic and NSO fractions are located in Appendix 3. From this set of
samples, eight were chosen for analysis by GC-MS. They are representative of
sediments that are unaltered, partially altered and extensively altered by the sill
intrusion.
A listing of the samples along with various parameters of the aliphatic
fractions is given in Table 2.5. The -a1kane CPI, a measure of the maturation, ranges
from approximately 5.5 in the sediments furthest away from the sill to 1 in the
sediments nearest to the contact zone. The ratio of pristane to phytane (Pr/Ph) is
usually around 0.5 in unaltered sediments, but becomes inverted in the oils and
thermally altered sequences. Therefore, these two molecular parameters are useful in
distinguishing the unaltered sequences from the altered sequences. The CPI and Pr/Ph
are plotted versus depth in Fig. 2.1 6a and 2.1 6b, respectively.
The mass fragmentograms m/z 191, representative of the triterpenoid
hydrocarbons, are presented in Fig. 2.1 7a 2.1 7h for the eight samples. The samples
away from the sill are dominated by triterpenes and
-hopanes, products of
diagenesis. The samples close to the sill have undergone thermal maturation, but a
(S/(S+R)) parameter of the C-22 carbon for the samples closest to
the sill range from 0.37 to 0.49. These ratios are not at the equilibrium ratio of 0.6
(Ensminger et al., 1974, 1977; Seifert and Moldowan, 1978) and indicate that full
thermal maturation has not been achieved.
Fragmentograms representative of the steroid hydrocarbons are presented in
Fig. 2.18a 2.18h. As with the triterpenoids, the steroids away from the sill are
measure of the
C31
diagenetic products, primarily sterenes. The steroid distributions near the sill are
dominated by C27 to C29 steranes, primarily the 5a(H),l4a(H),l7a(H)-20R isomers,
with lower amounts of the less stable 5(H),l4a(H),l7a(H)-20R isomers, a
distribution commonly found in hydrothermal oils (Kawka and Simoneit, 1987). A
dominance of the C29(20R) isomer in sample 481 A- 12-4 (55-65) suggests greater
contribution of a terrestrial steroid component (Huang and Meinschein, 1979).
Histograms of concentrations of the major PAH for the eight sediment samples
are shown in Fig. 2.19a 2.19h. These distributions range from perylene dominated in
20
the unaltered sequences to phenanthrene dominated in the altered sequences. Perylene
is primarily a diagenetically formed PAl-I (Louda and Baker, 1984) which is not stable
under hydrothermal conditions and is destroyed in the altered zones. The other PAH
in the histograms are derived pyrolytically and therefore the change from perylenerich to phenanthrene rich is another useful thermal maturity indicator. Diels'
hydrocarbon, a triaromatic steroid hydrocarbon used as a tracer of hydrothermal
alteration of organic matter, was detected in the altered zones, but the concentrations
were low compared to the concentrations found in seabed oils (Kawka, 1990).
The survey of the NSO fraction focused on the search for the ketones and the
isoprenoid phenols, the major components of the polar fractions of the seabed oils.
The fragmentograms representative of the alkanones are given in Fig. 2.20a 2.20h.
Alkanone distributions resembling those in the oils were found only in samples 481A12-4 (55-65) and 481A-13-2 (118-127). As with the seabed oils, the ketones in these
two altered sequences are present as several homologous series of 2-, 3-, 4-, 5-, 6-, 7(and higher) alkanones. They have no carbon number preference and the correlation
of their presence with the oil zone suggests that these ketones were formed during the
hydrothermal alteration of the sedimentary organic matter.
The isoprenoid phenols were found in samples 48lA-12-4 (55-65) and 48lA-
18-1 (30-32) but not in the altered sediment of 48lA-l3-2 (118-127). The mass
fragmentograms of m/z 122 and mlz 136, representative of the methyl and dimethyl
isoprenoid phenols, are presented in Fig. 2.21.
Downcore variations in the aliphatic and aromatic compositions in Hole 481 A
show a direct relationship to the thermal alteration of the sedimentary organic matter
from sill emplacement. The alkanones and isoprenoid phenols present in the seabed
oils were found only in the altered zones. Ketones are absent or occur in trace
amounts in oils (Tissot and Welte, 1984), although the homologous series of alkan-2ones are common constituents of recent and older marine sediments, they are generally
present with an odd-carbon number predominance (Brassell et al., 1980; Cranwell,
1977; Simoneit, 1978, 1979; Volkman et al., 1983). The ketones in the seabed oils
and thermally altered zones of the downcore sections are unique in that they are major
resolved components of the polar fractions exhibiting a smooth distribution, analogous
to the smooth -alkane distributions of the oils. Aliphatic ketones are commonly
found in oil shale pyrolysates (Regtop et al, 1982; Rovere et al., 1983), but only
recently have ketones been detected in sedimentary rocks exhibiting a CPI = 1
(George and Jardine, 199). In that study the ketones have been found in the
21
thennally altered sediments adjacent to a Proterozoic sill, indicating that there is a link
between the high temperature igneous alteration of sedimentary organic matter and
ketone formation.
The -alkylpheno1s present in the seabed oils in several homologous series also
exhibit a smooth distribution (CPI = 1) characteristic of a pyrolytic origin. But the
isoprenoid phenols present in the oils and altered sedimentary sequences occur only as
a few discrete isomers, structurally related to the tocopherols and sedimentary
chromans (Sinninghe Damsté et al., 1987). This suggests that these compounds or
related precursors could lead to the isoprenoid phenols. Of these two classes of
compounds, the chromans are more likely to be converted directly to the isoprenoid
phenols since they lack the additional phenolic hydroxyl groups present in the
tocopherols. Chromans have been identified in Guaymas Basin sediments (Kawka,
1990). A survey of the aromatic fractions of sediment extracts of Hole 481 A has also
identified these compounds, but in only trace amounts in the thermally-unaltered
zones. The most abundant isomer of the chroman series has three methyls on the
aromatic ring structure, but the most abundant isomer of the isoprenoid phenolic series
has only one methyl on the aromatic ring. These results argue against sedimentary
chromans being precursors to the isoprenoid phenols. One possible mode of origin is
that the isoprenoid phenols are bound to the kerogen matrix and preferentially released
under high temperature hydrothermal conditions. Thus, the presence of these phenolic
compounds is probably highly dependent on the organic source material and they are
therefore not good candidates as universal indicators of high temperature
hydrothermal processes.
However, if tocopherol or chroman related compounds are found to be
precursors of the isoprenoid phenols, it does indicate the preferential cleavage of the
ether bridge of the precursor structure, an indication that an acid-catalyzed reaction
under relatively extreme conditions is necessary (Siskin et al., 1990) for the reaction to
proceed. This is important because it identifies a type of ionic reaction, as opposed to
radical cracking reactions, as operating in the breakdown of the kerogen structure, a
class of chemical reactions often overlooked and only recently being emphasized as
possibly significant to the petroleum generation process (Siskin and Katritzky, 1991).
22
CONCLUSIONS
A survey of the poiar fractions of the seabed oils and sediment extracts of
hydrothermally-altered sequences has revealed that there are two major classes of
oxygenated compounds present, the ketones and the phenols. The smooth
distributions of the -alkylphenols and the alkanones (CPI = I) indicate a pyrolytic
source, analogous to the origin of jj-alkanes from the pyrolysis of sedimentary organic
matter. Their presence in the thermally-altered downcore sediments suggests that they
are formed by the sill intrusions and transported to the seabed by hydrothermal fluid
circulation. The isoprenoid phenols, occurring as a few isomers, are likely
hydrothermal alteration products of natural product precursors in the sediments. The
proposed structures of the isoprenoid phenols suggest that the precursors are
structurally related to the sedimentary chromans or tocopherols present in these
sediments.
23
Table 2.1. Location of oil covered hydrothermal vent samples.
Vent a
Location b
1972-CH1
not available
1983-CH1
4935, 4712
1984-CH1
4929, 4687
1984-CH2
4009, 3578
a Number refers to Alvin dive number, CH chimney sample
b Locations are given in transponder coordinates within the 1988 transponder array
24
Table 2.2a. Sample summary for DSDP Site 477.
Description b
Sample
Depth a
(mbsf)
a) 477-2-2 (145-150)
3.97
Olive brown diatomaceous ooze
b) 477-7-1 (88-90)
49.39
Diatomaceous ooze
c) 477-7-1(106-108)
49.57
Diatomaceous ooze
d) 477-16-2 (140-145)
117.93
Hydrothermally-altered clay siltstone
e) 477-16-2 (145-150)
117.98
Hydrothermally-altered clay siltstone
477-16-4 (130-135)
120.83
Hydrothermally-altered clay siltstone
g) 477-16-4 (135-140)
120.88
h) 477-17-1(145-150)
125.98
Hydrothermally-altered clay siltstone
Hydrothermally-altered silty siltstone
1)
i)
j)
k)
1)
m)
n)
o)
477-19-1(130-135)
477-19-1(135-140)
477-20-1 (135-140)
477-21-1 (52-57 + 91-96)
477-22-1 (110-115)
477-23-1 (90-95)
477-23-1 (CC)
144.83
144.88
154.37
163.25
173.12
182.47
182.80
Hydrothermally-altered siltstone
Hydrotherrnally-altered siltstone
Hydrothermally-altered claystone
Hydrotherrnally-altered silty clay
Hydrothermally-altered silty clay
Hydrothermally-altered silty clay
Hydrothermally-altered silty clay
a Depth (meters below seafloor) calculated according to DSDP convention (Curray et
al., 1982)
b Sample descriptions are from Curray et al. (1982)
25
Table 2.2b. Sample summary for DSDP Site 481A.
Description b
Sample a
Depth a
(mbsf)
a) 481A-4-2 (93-98)
73.0
Olive-brown Diatomaceous ooze
b) 481 A-6-5 (118-120)
98.2
c) 481A-6-5 (124-135)
98.3
Grayish-olive diatomaceous mud
Grayish-olive diatomaceous mud
d) 481A-7-6 (71-80)
107.3
Muddy diatomaceous ooze
e) 481A-8-7 (top of pipe)
108.5
Grayish-olive diatomaceous mud
f) 481 A- 12-4 (55-65)
151.6
Olive- to brownish-black silty clay
g) 481A-13-2 (118-127)
158.7
h) 481A-1 8-1 (30-32)
203.8
Brownish-black clay- and sandstone
Brownish-grey sandy clay
204.1
Brownish-grey sandy clay
223.6
Diatomaceous mudstone
Diatomaceous mudstone
i)
481 A- 18-1 (CC)
j) 481A-20-1 (110-115)
k) 481A-22-1 (65-70)
1) 481 A-22-7 (top of pipe)
m) 481A-22-7 (97-101)
n) 481A-24-CC
o) 481A-25-CC
p) 481A-26-CC
242.2
250.5
251.5
269.9
279.4
288.9
Mudstone
Mudstone
Silty claystone
Olive grey silty claystone
Claystone to silty claystone
a Depth (meters below seafloor) calculated according to DSDP convention (Curray et
al., 1982)
b Sample descriptions are from Curray et al. (1982)
26
Table 2.3. Bulk characterization of seabed chimney oils.
Sample
Fl (%)
F2 (%)
F3 (%)
Asphaltenes (%)
1972-CH1 Interior
63.8
4.8
15.8
15.6
1972-CH1 Exterior
39.9
12.3
20.0
27.8
1983-CH1 Interior
68.5
5.8
20.5
5.2
1983-CH1 Exterior
54.6
10.2
25.3
9.9
1984-CH1 Interior
71.0
3.4
20.3
5.3
1984-CH1 Exterior
36.1
15.2
29.3
19.4
1984-CH2 Interior
31.1
15.8
31.5
21.6
1984-CH2 Exterior
29.8
16.3
32.7
21.2
27
Table 2.4. Summary of molecular parameters for hydrothermal vent oils.
Hydrocarbons
Ketones
Sample
-Alkane Cmax Pr/Ph Pr/-C17
range
1972-CH1 Interior
12-27
18
1.3
0.79
1972-CHI Exterior
1983-CH1 Interior
12-25
18
1.3
12-25
18
1 983-CH 1 Exterior
12-24
1984-CH1 Interior
Ketone
range
Cmax
0.51
12-29
22
4.25
3.31
15-25
20
1.4
0.87
0.65
12-28
21
16
1.6
1.27
0.93
12-26
19
12-29
20
1.1
0.94
0.70
12-31
23
1984-CH1 Exterior
12-28
19
1.4
1.37
0.87
12-30
21
1984-CH2lntenor
12-25
16
1.5
0.85
0.66
11-25
15
1984-CH2 Exterior
11-25
15
1.7
1.03
0.82
11-25
15
Ph/n-C18
Table 2.5. Selected parameters for the aliphatic fractions of DSDP Leg 64 Hole 481 A.
Samples (Leg 64, Hole 481A)
Parameter
4-2
8-7
(93-98) (top)
12-4
13-2
20-1
18-1
22-7
26-CC
(55-65) (118-127) (30-32) (110-115) (top)
n-alkane
range
12-33
12-32
12-35
12-38
12-38
12-31
13-31
13-33
CPI
4.09
3.60
1.87
1.20
1.60
n.d.
4.13
5.46
Cm
29
29
29
15
15
15,29
29
29
Pr/Ph
n.d.
0.47
1.51
1.75
2.09
0.34
0.45
0.50
Pr/n-C17
n.d.
0.31
2.16
0.54
2.14
5.96
1.17
1.54
Phin-C18
n.d.
1.04
1.79
0.34
1.21
14.85
4.43
4.8
0.37
0.49
.048
0.42
.048
1.79
2.89
2.16
0.74
2.01
1.08
1.73
2.09
1.61
2.35
1.57
0.35
1.24
0.46
1.10
S/(SR)
C31
S/(S+R)
C32
29.30.31H
29,30,31M
-
27R129R
-
27R128R
28R/29R
-
n.d. = not determined
S/(SR) = C-22 S and R epimer ratios for C31 and C32 a-homohopanes
C31 ct-hopanes
29,30.31 H
C29 + C30
29,30,3 1 M
C29 + C30 + C31 moretanes
27R
29R
C27 20 R aaa-sterane
C29 20 R actct-sterane
27R
28R
C27 20 R actct-sterane
28R
29R
C28 20 R aaa-sterane
C28 20 R aaa-sterane
C29 20 R ctctc-sterane
-
29
112°W
IIIw
Z758 N r
30°N
105°W
Figure 2.1. (a) Map of Gulf of California showing geographic location of the sampling
area, and (b) Map of Guaymas Basin showing its two rifts, with locations of DSDP
Sites (Simoneit, 1991).
30
//
/
/
South
//
(i_
/ West Hill
270 02'
,41
y//flfEast
-1
.I///J'-iiii
j4774 /j/9
Orn
J
.7
...........
7..
(2741,3556)..
/
...
7
1982 ..fRegion
of
/
I,
Buried Mounds
/
270 01'
ij/
/
/'?'
/
\
17
:
Angel Rock
/7
J
/i
1'
7
(\;r
/
I
)
"11981
/
/
I
/
/
/
/ç
\I983I
/\
/ /
// /
"B
(4111,0)
/
I984'
Mounds
Hily
/
1/
/
(
Buried
I /
I
//
/
I! /
270 N
y//////
\;%"$/
/ // 7
/1//I
/J //\
'/1Y/// /
/ A /// / 7/
/ / // /
/ / / 'A /
,...."PHydrothermal Mound
Systems
/ / /o,0)/
1110 25' W
1110
260 59
Fault Scar p
.'
24'
Extent of Shallow Sill
111023'
Figure 2.2. Bathymetric chart of the southern rift of Guaymas Basin with general
study area of Alvin dives during March, 1988. The transponder array with its x,y
coordinates is also indicated (Simoneit, unpublished report, 1988).
31
HOLE 477A
HOLE 477
Water depth - 2003 m
-;
-2IZ-:.: * 03
UNIT I
o
0l,ve brown diatom
ooze and turbidites
1
__/
'.
1
2
3
_
Coarse-grained
dolerite sill
<
(
-'
-
-
_____________
UNIT II
-
iI
11
13
100-
15
h
U-
?
>< -:
-
/
100p
I
Hydrothermally
altered terrigenous
turbidites and mud
Hi
17
18
21
-
-
7
:::::
4
200
A
=
Anhydrite
P
=
=
=
Pyrite
Epidote
Hydrothermal
sediment
E
6
7
8
-9
10
I--
E
11
Figure 2.3a. Lithologic column for site DSDP Site 477, lowercase letters refer to
sample locations listed in Table 2.2a (Curray et al., 1982).
32
HOLE 421
Water depth
HOLE 481A
*
1998 m
UNIT I
0111
-.
-'rt
- - .z_
turbidites
I
1
6
e-
8
-::_____
5
hcd-
ooze and
Megaturbidite
-
i[!I.1
::---
Olive brown
muddy diatom
2
6
4
1
Megaturbudite
7
10
5>..
a
a
E 2000
0
0
iii-
17
L
J-
C,,
Sandstone
p
-
Chert and
dolente sills
complex
'
'
_::::
-
UNIT II
21
23
-
z-:=:
19
.0
.0
----.
I
-_i-=
j
15
c
I
ILaminated
-.__-
diatom mud
j
Mudflow II
4
300-
026 27
Mudflow Ill
!
Dolerite
32
33
Dolerite
35
36
37
Figure 2.3b. Lithologic column for site DSDP Site 481 A, lowercase letters refer to
sample locations listed in Table 2.2b (Curray et al., 1982).
33
D Aliphatic Fraction
0
Aromatic Fraction
NSO Fraction
Asphaltenes
o
Aliphatic Fraction
Aromatic Fraction
NSO Fraction
Asphaltenes
1972-CH1 Interior 1972-CHI Exterior
100
75
0
50
25
0
1983-CH1 Interior 1983-CH1 Exterior
Figure 2.4. Histograms of bulk class percentages for chimney samples (a) 1972-CH1
and (b) 1 983-CH 1.
34
100
o
Aliphatic Fraction
E] Aromatic Fraction
E NSO Fraction
Asphaltenes
'1.)
U
50
25
[II
1984-CH1 Interior 1984-CH1 Exterior
100
0 Aliphatic Fraction
0 Aromatic Fraction
fl NSO Fraction
50
C-)
Asphaltenes
25
n
1984-CH2 Interior 1984-CH2 Exterior
Figure 2.4. Histograms of bulk class percentages for chimney samples (c) 1984-CH1
and (d) 1984-CH2.
35
100% AROMATIC 1-IC
70-28
((72-I
((77-20
172-IA
((77-2C__________1 703
11738
.1(72-3
((72-2
aq.
((7
70-4A8
ll77-48
(
70-5A
aS'4C..#a
___..Ij-Ca4Z
r
((68-1-2
-.l1V4-C.al.
I ,.I 1
1
1173-3
-3B
- C4
I 00%
ALIPHATIC HC
IN 1
a
100%
NSO*ASPHALTENE
COMPOUNDS
Figure 2.5. Ternary diagram of the bulk compositions for seabed hydrothermal oils.
(adapted from Kawka and Simoneit, 1987).
36
1972-CH1 Interior
I
Aliphatic Fraction
I
H
I
ij
I
I
I
12
I
1
ft
2'
______
21.
Aromatic Fraction
NSO Fraction
A
ic
20
21
22 23
.
Time
Figure 2.6. Gas chromatograms of 1972-CHI Interior: (a) aliphatic fraction; (b)
aromatic fraction; (c) NSO fraction. Numbers refer to carbon chain length of the nalkanes and ketones, Pr = pristane, Ph = phytane, A = isoprenoid phenol (MW = 388),
B = isoprenoid phenol (MW = 402).
37
1972-CH1 Exterior
&
Aliphatic Fraction
Aromatic Fraction
NSO Fraction
202'
fl
A
I
Time
Figure 2.7. Gas chromatograms of 1972-CHI Exterior: (a) aliphatic fraction; (b)
aromatic fraction; (c) NSO fraction. Numbers refer to carbon chain length of the nalkanes and ketones, Pr = pristane, Ph = phytane, A = isoprenoid phenol (MW = 388),
B = isoprenoid phenol (MW =1102).
RIC
2500
83:20
2808
56:40
1500
50:88
1808
33:28
508
16:40
27..
7.3
108.8-
2c
sql
I
TOThL.
Id
t
Iit 26
U.
'3
52
I
1tL
rjJi VM
I
2508
83:20
2080
66:48
isee
50:88
ieee
33:20
508
16:48
100.8
I4LLLJ kJIL lit
J1
21
VI
23
c)
20
TOTj
2c
k
.1
1408
46:40
1508
1600
58:88
53:20
1788
56:48
1800
1900
60:80
63:20
Figure 2.8. NSO fraction of hydrothermal oil from the interior of vent 1972-CHI: (a)
reconstructed ion chromatogram (RIC); (b) representative mass fragmentograms for
ketones (mlz 57 + 58 + 71 + 72) of oil covering the same scan range; (c) expanded
scale identifying resolved ketone isomers. Numbers refer to carbon chain length.
39
A
leci.0-1
c)
122
'3
34.5i
)
136
1øø..-1
c)
C.
.- /z.
152
1850
61:40
1900
63:20
1950
65:00
2000
65:48
2050
68:20
2100
70:80
Figure 2.9. NSO fraction of hydrothermal oil from the interior of vent 1 972-CH 1: (a)
representative mass fragmentogram for the isoprenoid phenol compound A (m!z 122);
(b) representative mass fragmentogram for the isoprenoid phenol compound B (mlz
136); (c) representative mass fragmentogram for the isoprenoid phenol compound C
(mlz 150).
12
100.0
1
so. o
57
161
91
189
278
223
3
1
I i'l,
M/E
250
200
150
50
350
458
1
180.0-i &)
50.0
74
224
181
266
ti/E
150
108
50
382
33 367
1tf IrE. rIt
ii:rJi.i..
250
300
350
450
250
388
358
458
100.81 c)
,. j
108 135
83
1163
1
(fl
M/E
58
108
150
Figure. 2.10. Mass spectra and proposed structures of isoprenoid phenols present in
NSO fraction of hydrothermal oil from the interior of vent 1 972-CH 1: (a) compound
A; (b) compound B; (c) compound C. Mass spectra correspond to the peaks labeled in
Fig. 2.9.
41
A
100.01 o.)
"IL
i3'
543i
208
2.51
)
222
1888
60:80
1988
63:20
2000
66:40
2100
78:00
2200
73:20
2308
76:40
2480
80:00
2500
83:20
2600
86:48
Figure 2.11. Silylated NSO fraction of hydrothermal oil from the interior of vent
1 972-CH 1:
(a) representative mass fragmentogram for the isoprenoid phenol
compound A' (mlz 194); (b) representative mass fragmentogram for the isoprenoid
phenol compound B' (mlz 208); (c) representative mass fragmentogram for the
isoprenoid phenol compound C' (mlz 222).
42
I
100.01
)
457
119 149
,85
1?
272
II,1I I.Ip.II.1I.I..I1I.
M/E
100
50
387 48 445
306 337
111.1
I
158
250
388
350
480
450
100.81
0
261
100
-
1iG.
321
42
400
380
200
356 389
222
-
C)
50.0193
73
1
M/E
P
'I
100
26G
p LIE.
V
200
i.
. .k.1
.i
II
300
480
Figure. 2.12. Mass spectra of silylated isoprenoid phenols present in NSO fraction of
hydrothermal oil from the interior of vent I 972-CH 1: (a) compound A'; (b) compound
B'; (c) compound C'. Mass spectra correspond to the peaks labeled in Fig. 2.11.
43
348
35,
338
404
418
432
446
450
474
488
502
516
530
544
558
1600
53:28
1888
60:08
2088
66:40
2200
73:28
2480
80:80
2680
86:40
Figure 2.13. Representative mass fragmentograms (M) for the silylated derivatives
of the extended C19 to
C34
a-alkylphenols present in the NSO fraction of
hydrothermal oil 1972-CH1 Interior. Compounds A' and B' refer to the isoprenoid
phenols.
01
460
91.
474
66.
488
2150
71:48
2200
73:20
2250
75:88
2388
76:40
2358
78:28
2480
88:00
Figure 2.14. Representative mass fragmentograms (M) for the silylated derivatives
of the extended
C27
to C29 ji-alkyiphenols present in the NSO fraction of
hydrothermal oil 1972-CH1 Interior. Labeled in the figure are series C, D and E.
45
120.O-i cI)
.
1
50.0
120
68 94
I
I
Ii
'i iiI'
M/E
50
S
1IIiI
I
418 438
i
250
150
180
358
450
400
1
50.0
F
128
2
219
iljj
4
Ii
I
I
I'
?1/E
100.01
58
158
I
I
258
358
458
400
cJ
50.0
1
261
13S4
.111
tilE
50
1
150
258
350
1,11. II.J.
408
42J
I
4
I
450
Figure 2.15. Mass spectra of silylated u-alkylphenols present in NSO fraction of
hydrothermal oil from the interior of vent 1 972-CH 1: (a) compound Cl; (b) compound
C2; (c) compound C3. Mass spectra correspond to the peaks labeled in Fig. 2.14.
1
180.81 a)
73
1
37
294
1'1111
I.III
350
300
250
15 132
I
:I
1
1411r'i.
M/E
iOe
50
1T
158
414 445
400
458
18
a)
50.0-i
71
85
I
1
I'
18
50
M/E
158
288
300
250
458
350
50.8-
J7
377
:
Ills?
I
M/E
132
I If
50
100
251
306
351
473
405
ii.i.i. 111.1.1.1. lI,I.l..I,lII,r, I.I.l.t. Itl.
150
258
300
350
480
450
500
Figure 2.15. Mass spectra of silylated n-alkylphenols present in NSO fraction of
hydrothermal oil from the interior of vent 1972-CHI: (d) compound Dl; (e)
compound D2; (f) compound D3. Mass spectra correspond to the peaks labeled in
Fig. 2.14.
47
1
100.01 i)
106
1
L
I
I
iti.Ilj r
J
50
Pi/E
150
180
258
358
39
445.
510
I IIJI I
I.t,IlI III.
488
450
588
108.01
50.0
1
iLl g
. r.
50
M/E
121
149
1
108
158
458
1
180.01
)
50.0
348
ti'E
50
108
158
258
358
450
Figure 2.15. Mass spectra of silylated -a1ky1pheno1s present in NSO fraction of
hydrothermal oil from the interior of vent 1972-CHI: (g) compound El; (h) compound
E2; (i) compound E3. Mass spectra correspond to the peaks labeled in Fig. 2.14.
G)0
50'
Sc
100
150
NNN
150
< p7 A.''.
A
A
A
A
4.
4.
SILLA
V
-)
l
< A
200
250
250
300 t
I
2
4
3
cPI
5
6
0.0
i.i.i.i. I
0.5
1.0
1.5
2.0
2.5
Pr/Ph
Figure 2.16. Plots of molecular parameters versus depth in DSDP Leg 64 Hole 481 A:
(a) CPI vs. Depth, meters below sea floor (mbsf) and (b) Pr/Ph vs. Depth (mbsf).
49
_c.,c.
108.8
1
1°r -:7(21)
191
1c,o,
T°
c31p3
I
100.0
191
C3,p3
18.8
C30 -'
c)
191
I
c2
c32-
5
C33
A.4 .&
--
c3o
d)
131
c2.,"
c31",
C
-
J
C33
ssz
Co'9
C3ç"(3
-
ill
2800
66:48
2188
78:88
2208
73:20
2308
76:40
2488
88:80
2500
83:20
2688
86:40
Figure 2.17. Representative mass fragmentograms m!z 191 for the triterpenoid
hydrocarbons in the bitumen of DSDP Leg 64 sediments: (a) 481 A-4-2 (93-98); (b)
481A-8-7 (top of pipe); (c) 481A-12-4 (55-65); (d) 481A-13-2 (18-27).
50
180.
81 e)
C2?
191
C3o(3e
-
-
191
C2.:1
C30
(3
LI
IitI
1-----
188.01
C;1
.----.-t
1-
-.-.
)
191
r?(T
C3:ff5
-,-
_:-i---:'-'=
-
--I-
L.)
191
C3,
I
-
2088
66:48
-
2188
78:88
I
-
2208
73:20
Ii
.. -
.
..1
I.
2380
76:48
-. -.. -n..
2488
80:00
2500
83:20
-
2600
86:40
Figure 2.17. Representative mass fragmentograms mlz 191 for the triterpenoid
hydrocarbons in the bitumen of DSDP Leg 64 sediments: (e) 481 A- 18-1(30-32); (f)
481A-20-1 (110-115); (g) 481A-22-7 (top of pipe); (h) 481A-26-CC.
1000)
27
TOT
26
1808
68:00
isee
63:20
2888
66:48
21
2108
70:00
2200
73:20
2300
76:40
Figure 2.18. Representative mass fragmentograms (mlz 215, 217, 218, 257, 259) for
the steroid hydrocarbons in the bitumen of DSDP Leg 64 sediments: (a) 481 A-4-2
(93-98); (b) 481A-8-7 (top of pipe); (c) 481A-12-4 (55-65); (d) 481A-13-2 (18-27).
52
lO0.0-
e)
27
zc
c'f
2I
..
31?
102.01
(31
I
..
-FT)
27
28
TOT
R
r
)
2
it
pR
A
II
1 5)
21
27
TOT
2S
28
'
I
'
I
120.01
I
27
-
TOT
28
zo
27
L
JL.
I
Figure
1800
1900
60:00
63:20
2.18.
I
4
I
I
2800
66:40
2100
72:00
Representative mass fragmentograms (mlz
2200
73:28
2302
215, 217, 218, 257, 259)
for
the steroid hydrocarbons in the bitumen of DSDP Leg 64 sediments: (e)
(30-32); (f) 481A-20-1 (110-115);
76:40
481A-18-1
(g) 481A-22-7 (top of pipe); (h) 481A-26-CC.
53
600
481A-4-2 (93-98)
500
400
300
0
200
100
0
1500
48tA-8-7 (top)
-
1250
1000
E-
750
g500
0
250
0
200
481A-12-4 (55-65)
150
100
4)
0
50
0
800
481A-13-2 (118-127)
1600
400
tI
0
0
200
0 r..
0
0
C
C
)
C
c.,
C
0
C
0
0
C
C
C
0
C
C
0.
0
0
C
0
C
0
C
4)
C
0
0
C
4)
-
=
C
C,
4
0.
a
-
v
0
c
0
Cl
0
0
0
.
'4-
C
9
C
C
0
Figure 2.19. Histograms of the major aromatic compounds present in the bitumen of
DSDP Leg 64 sediments: (a) 481A-4-2 (93-98); (b) 481A-8-7 (top of pipe); (c) 481A12-4 (55-65); (d) 481A-13-2 (18-27).
54
200
e
481A-18-1 (30-32)
150
.
100
C)
C
C
50
0
1500
481A-20-1 (110-115)
1250
C)
CC
..E.
1000
750
g500
U
250
0
2500
481A-22-7 (top)
2000
1500
F°°°
500
0
k)600
48 LA-26-CC
500
C)
CC
400
.E.
U
300
200
0' . -..
100
C)
C)
C)
0
C
C
C)
C
C)
C)
C)
C
C)
=
C)
C)
C
C
C)
C)
C
-
.
N
c
c
C
C)
c
.
C)
C)
0
U
C)
U
a
-
N
C
Q
x
x
:
:
0
CC
C
N
C
C')
C
N
2:'
0
Figure 2.19. Histograms of the major aromatic compounds present in the bitumen of
DSDP Leg 64 sediments: (e) 481A-18-1 (30-32); (t) 481A-20-1 (110-115); (g) 481A22-7 (top of pipe); (h) 481 A-26-CC.
55
10O.0-
108.81 b)
TOT
108.0-
c)
100
TOT
500
16:40
1800
33:20
1508
50:00
2000
66:48
2588
83:28
Figure 2.20. Representative mass fragmentograms (mlz 57, 58, 71, 72) for the ketones
in the bitumen of DSDP Leg 64 sediments: (a) 481 A-4-2 (93-98); (b) 481 A-8-7 (top of
pipe); (c) 481A-12-4 (55-65); (d) 481A-13-2 (18-27).
100.01 c)
100.01
)
100.81
)
500
16:48
1000
1500
33:20
50:08
2000
66:40
2500
83:20
Figure 2.20. Representative mass fragmentograms (mlz 57, 58, 71, 72) for the ketones
in the bitumen of DSDP Leg 64 sediments: (e) 481A-18-1 (30-32); (f) 481A-20-1
(110-115); (g) 481A-22-7 (top of pipe); (h) 481A-26-CC.
57
''-
108.8j
122
I
44.
136
100. @-i
Jb)
122
I
56.
136
1950
65:00
2000
66:40
2050
68:28
2100
78:08
2158
71:40
2280
73:20
2250
75:00
Figure 2.21. Representative mass fragmentograms (mlz 122 and mlz 136) for the
isoprenoid phenols in the bitumen of DSDP Leg 64 sediments: (a) 481 A- 12-4 (55-65)
and (b) 481A-18-1 (30-32).
58
CHAPTER 3
Radical and Ionic Reactions During Hydrothermal Pyrolysis of Organic Matter:
Implications for the Simulation of Geochemical Processes
ABSTRACT
The heavy water pyrolysis experiments of Messel shale and model compounds
performed by Hoering have demonstrated that there can be a large exchange of
protons between water and organic compounds during hydrous pyrolysis. There has
not been a satisfactory explanation for these results, especially the aspects of the
extent of deuterium substitution in the n-alkanes and the enrichment of deuterium at
only one end of some molecules.
The following mechanism accounts for the deuterium substitution observed in
the hydrocarbons generated during Messel shale heavy water pyrolysis. Thermal
cracking of the aliphatic kerogen network during hydrous pyrolysis generates jjalkanes and a-olefins. The a-olefins are quickly converted to internal olefins by acidcatalyzed double bond isomerization, a process which rapidly incorporates deuterium
into the hydrocarbon skeleton. Deuterium exchange by direct homogeneous radical
exchange with saturated hydrocarbons occurs at a much slower rate. The olefins are
subsequently hydrogenated to fully saturated n-alkanes, but the rate of alkene
isomerization is much greater than the rate of hydrogenation. Aliphatic moieties
bound to the kerogen at one site can form a terminal double bond upon cleavage.
Acid-catalyzed double bond isomerization followed by hydrogenation preferentially
introduces deuterium at only one end of the molecule, resulting in hydrocarbons with
unsymmetric patterns of deuterium incorporation. This mechanism accounts for the
extensive deuterium substitution observed in the generated -alkanes and also explains
how deuterium substitution can occur at only one end of selected hydrocarbon species.
INTRODUCTION
The research by Hoering (1984) produced some interesting results concerning
the role of water during laboratory hydrous pyrolysis. Presented below are some key
aspects from that publication, a paper which was divided into three parts:
(1)
hydrous pyrolysis of shale kerogen to evaluate the similarities and
differences between artificially derived oils and natural oils,
(2)
the pyrolysis experiments in D20 with deuterium used as a tracer to
understand how water interacts in the catagenetic reactions,
(3)
pure compound D20 pyrolyses to aid in understanding the
mechanisms of organic matter transformations.
Messel shale was selected for the experiments due to its low thermal history, its high
organic carbon content, and having been a sample for numerous studies. The shale
was powdered and extracted prior to heating. For each experiment the shale was
combined with water or heavy water, sealed under nitrogen in a stainless steel reaction
vessel and heated at 330°C for 72 h.
The -a1kanes from the D20 pyrolysis were isolated and analyzed by mass
spectrometry to determine the extent of deuterium incorporation. Fig. 3.1 is a
histogram of an unweighted average deuterium distribution for the C17 to C29 palkanes generated from the kerogen by hydrous pyrolysis. The substitution ranged
from 0 to at least 14 deuterium atoms for each n-alkane, with the highest relative
abundances of 4 to 6 deuterium atoms. There was no obvious trend in substitution
pattern as a function of chain length.
The analysis of isoprenoid and branched hydrocarbons generated by the D20
pyrolysis experiments provided additional information about the nature of the
deuterium exchange process. Fig. 3.2 is a histogram showing the relative abundances
of the C13 ion fragments from the mass spectrum of pristane generated in the D20
experiment. The bimodal distribution is consistent with a pristane molecule which has
deuterium substituted at only one end of the molecule. The C13 fragment which
contains no deuterium atoms would produce an ion fragment of m/z 183 while the
C13
fragment containing the deuterium atoms would produce ion fragments greater than
mlz 183, and in this case maximizes at mlz 190, corresponding to 7 deuterium
substitutions as being the most abundant isomer. The preferential deuterium
61
enrichment to only one end of certain molecules was also evident in the analysis of
iso- and anteiso-alkanes.
Fig. 3.3 is the partial mass spectrum of 2-methyl
heptadecane, a compound representative of the branched hydrocarbons produced in
the pyrolysis experiments. The cluster of ion fragments maximizing at mlz 247
corresponds to loss of a methyl group with 8 deuterium substitutions being the most
abundant. The cluster at mlz 216 is produced by the loss of a propyl group with 5
deuterium substitutions being the most abundant. These patterns of the mass
fragments are also consistent with an enrichment of deuterium at one end of the
molecule. But contrary to the original interpretation, this molecule appears to be
enriched with deuterium at the end where the branching occurs. Analysis of sterane
and triterpane hydrocarbons also revealed a preferential enrichment at one end of the
molecule (Hoering, 1984).
In an attempt to understand the mechanism of deuterium enrichment in the
hydrocarbons, pyrolyses of some model compounds were performed. Below is a
discussion of the results from the alkane arid alkene D20 pyrolyses from the original
Hoering (1984) publication.
Docosane was selected to study the degree of deuterium incorporation by
simple homogeneous exchange. Under the same heating conditions as those in the
Messel shale pyrolyses (72 hr @ 3 30°C) there was a small amount of deuterium
exchange with the fully saturated alkane. Fig. 3.4a is a histogram of the results
showing the relative amounts of the deuterium substituted isomers. Another
experiment was conducted using the olefin 1 -octadecene as the molecular probe. This
compound was chosen since dry pyrolysis experiments usually generate a large
amount of olefins. Under the same reaction conditions the olefin was hydrogenated to
the saturated octadecane, indicating a strongly reducing environment inside the
reaction vessel. Analysis of this product showed that a substantially higher amount of
deuterium incorporation occurred before the olefin was converted into the fully
saturated reaction product octadecane. A histogram of the relative amounts of the
deuterium substituted isomers is shown in Fig. 3.4b. These results indicate that the
deuterium exchange process is enhanced by the presence of a double bond, but the
presence of only one double bond is not sufficient to explain the extent of deuterium
substitution observed in the -alkanes generated by the D20 Messel shale pyrolysis,
shown in Fig. 3.1.
To explain the deuterium substitution patterns in the pyrolysis experiments, a
free radical chain mechanism was proposed. One set of reactions is shown in Fig. 3.5
62
(Hoering, 1984). This mechanism proposes that one part of the multiple deuteration
could have occurred by the free radical migration of the olefin sites.
A re-examination of the Hoering (1984) deuterium isomer profile data by
numerical modeling was performed by Ross (1992a,b). He concluded that one likely
explanation for the deuterium isomer distribution in the -alkanes generated in the
D20 Messel shale pyrolysis is by simultaneous deuterium exchange at more than one
site. He suggested a combination of ionic and radical chemistry to explain the results,
shown in Fig. 3.6 (Ross, 1992a), although the details of the actual chemical
mechanisms to result in preferential deuterium substitution at one end of the molecule
could still not be fully explained.
Recent research in pyrolysis and high temperature aqueous chemistry of
hydrocarbons provides some insight into the major reactions that alkanes and alkenes
undergo (Weres et al., 1988; Siskin et al., 1990; Kissin, 1987, 1990; Leif et al., 1992).
These studies point to the importance of both radical and ionic reaction mechanisms
during the pyrolysis of organic matter. This chapter duplicates the original Hoering
(1984) Messel shale pyrolysis experiments and presents results from additional
hydrous pyrolysis experiments which provide evidence for the chemical pathway by
which hydrogen exchange occurs between water and aliphatic hydrocarbons.
EXPERIMENTAL
Chemicals and samples. H20 pyrolysis experiments were performed using
Burdick and Jackson ultrapure water, and D20 pyrolysis experiments were done using
D20 from Cambridge Isotope Laboratories. The D20 was glass distilled before using.
Aliphatic compounds used in pyrolysis experiments were 1,1 3-tetradecadiene (purity
> 97), 1-hexadecene (purity > 97%), eicosane (purity 99%), dotriacontane (fl-C32H66,
purity > 97%), and low-density polyethylene (LDPE, purity > 99%).
Sublimed
elemental sulfur was used in one of the pyrolysis experiments. The Messel shale used
in the experiments was powdered and Soxhlet extracted with methanollmethylene
chloride for 72 hr prior to the pyrolysis studies. One surface sediment sample from
Guaymas Basin, Gulf of California, was pyrolyzed at 350°C for 72 hr and extracted
with methanol and methylene chloride prior to this study.
Hydrous pyrolysis experiments. Pyrolysis experiments were performed in
SnoTrik® T316 stainless steel high pressure pipes rated at 60,000 psig (4080 bar),
sealed with end caps and heated in an air circulating oven set at 330° ±2°C. The
reaction vessels with reactant mixtures were placed in a glove bag and flushed with
five volumes of argon. Deoxygenated H20 or D20, prepared by bubbling with argon
gas for 45 minutes, was added and the vessels sealed. Durations of the heating
experiments ranged from 1 hr to 72 hr (Table 3.1).
Extraction and fractionation. The reaction vessels were removed from the
oven and cooled to room temperature upon completion of the heating cycle. The
reaction vessels were extracted with two 1 mL portions of methanol followed by five 1
mL portions of methylene chloride. The solvents and water from each pyrolysis
experiment were combined in a centrifuge tube and the organic fraction separated and
collected. The water was extracted with two additional portions of methylene chloride
and the two methylene chloride fractions were combined. The methylene chloride was
dried with anhydrous sodium sulfate and was passed through an activated copper
column to remove the elemental sulfur. The solvent was removed to near dryness
using a rotary evaporator at 30°C. The total extract was made up to 2 mL of
methylene chloride and deasphalted in 100 mL of heptane. The asphaltenes were
allowed to precipitate overnight and removed by filtration. The deasphalted fractions
were fractionated by column chromatography (30 cm x 1 cm) packed with 3.8 g
alumina (fully active) over 3.8 g silica gel (fully active). The samples were separated
into three fractions by elution with 50 mL heptane (nonpolar, Fl), 50 mL toluene
(aromatic, F2) and 25 mL methanol (polar NSO, F3). Separation of the alkanes from
the alkenes was done by argentation silica column chromatography. In one
experiment the normal alkanes were isolated from the nonpolar fractions by urea
adduction. Hydrogenation of selected samples was done by bubbling H2 gas into the
sample for 30 mm. in the presence of platinum(IV) oxide (Adam's catalyst).
Gas chromatography. Gas chromatography (GC) of the pyrolysates was
performed with a Hewlett Packard 5890A equipped with a 30 m x 0.25 mm i.d. DB-5
open tubular column (0.25 p.m film thickness). The GC oven was heated using the
following program: isothermal for 2 mm. at 65°C, 3°/mm. to 310°C, and isothermal
for 30 mm., with the injector at 290°C, detector at 325°C, and helium as the carrier
gas.
Gas chromatography-mass
Gas chromatography-mass spectrometry.
spectrometry (GC-MS) was performed on a Finnigan 9610 gas chromatograph
coupled to a Finnigan 4021 quadrupole mass spectrometer operated at 70 eV over the
mass range 50-650 dalton and a cycle time of 2.0 s. The GC oven temperature was
programmed at isothermal for 2 mm. at 65°C, 4°/mm. to 3 10°C, and isothermal for 30
mm., with the injector at 290°C, and helium as the carrier gas. The MS data were
processed with an on-line Finnigan-Incos 2300 computer data system.
Additional analyses were performed on a Hewlett Packard 5890 Series II GC
coupled to a Hewlett Packard 5971 Series Mass Selective Detector (MSD). The GC
was equipped with a 30 m x 0.25 mm i.d. DB-1 open tubular column (0.25 pm film
thickness). The GC oven temperature was programmed at isothermal for 2 mm. at
100°C, 5°/mm. to 260°C, 10°C/mm. to 300°C, and isothermal for 10 mm., with an oncolumn injector, and helium as the carrier gas. The MS data were processed with a
Hewlett Packard Vectra 486 PC.
65
RESULTS AND DISCUSSION
pyrolysis experiments. To more fully understand the factors
affecting the aqueous high temperature organic chemistry of heavy n-paraffins,
pyrolysis of fl-C32H66 with water only or water with inorganic additives has been
studied (Leif et al., 1992). Each experiment was run at 350°C for 72 hr under a
nitrogen atmosphere. It has been shown that extensive cracking, with varying degrees
of alkene formation, occurred under the experimental conditions. The composition of
the products was modified by pH and reactive species such as elemental sulfur and
iron sulfides. Fig. 3.7 shows the gas chromatograms of the total extracts from these
pyrolysis experiments. They are characterized by a broad distribution of cracking
products with a large amount of unreacted starting material. The recovered cracking
products ranged in carbon number from C9 to C31, there was a negligible amount of
gas pressure in each of the reaction tubes which escaped upon opening. The cracking
products in all of the experiments maximized at C16, half the carbon number of the
starting material. The aliphatic fraction consists -alkanes and -alkenes. Fig. 3.8a is
the aliphatic fraction of the n-C32H66 H20 system, consisting of -a1kanes and
several -a1kene isomers. Catalytic hydrogenation of the nonpolar fraction confirms
the presence of only -a1kene isomers (Fig. 3.8b). The large number of -a1kene
isomers is evidence of acid-catalyzed double bond isomerization. The experiment was
repeated in an alkaline environment maintained by the addition of NaOH. The
chromatograms of the nonpolar fraction and hydrogenated nonpolar fraction are
shown in Fig. 3.9a and 3.9b. The low hydrogen ion concentration in the alkaline
system inhibited double bond migration to give a product distribution dominated by
terminal a-alkenes. These results show that the products from these pyrolysis
experiments are the result of primary cracking of -C32H66 to form terminal alkenes,
followed by secondary acid-catalyzed reactions of these terminal n-alkenes to form a
suite of internal n-alkenes. The extent of double bond isomerization in the water
system indicates that there can be significant proton exchange between water and
hydrocarbons by this pathway.
To measure the amount of proton exchange that can occur by acid-catalyzed
double bond isomerization, the above experiments were repeated using D20. The
chromatograms of the -C32H66 -D20 system are shown in Fig. 3.10. As before, the
products consist of n-alkanes and several n-alkene isomers. The saturated and
unsaturated hydrocarbons were separated by AgNO3 column chromatography.
Deuterium substitution in the ii-alkanes was negligible while there was extensive
deuterium substitution in the alkenes. Figure 3.11 shows the mass spectrum of -C17
of the alkane fraction (Fig. 3.1 la) and the mass spectrum of U-C17 from the
hydrogenated alkene fraction (Fig. 3.11b). Fig. 3.12 shows the results from the
C32H66 -D20 - NaOD system. The alkaline system greatly reduced the amount of
deuterium substitution in the hydrocarbons. Figure 3.13 shows the mass spectrum of
-C17 of the alkane fraction (Fig. 3.13a) and the mass spectrum of u-C17 from the
hydrogenated alkene fraction (Fig. 3.1 3b). These results indicate that no deuteration
occurred under these conditions, neither in the alkane fraction nor in the alkene
fraction. Since alkaline conditions should inhibit the acid-catalyzed chemistry but not
affect the free radical chemistry, the above experiments indicate that direct exchange
between D20 and a-alkanes does not occur under these conditions. The major
pathway for the deuterium exchange under these conditions appears to be an ionic
rather than a radical mechanism.
Pyrolysis of 1.1 3-tetradecadiene, 1 -hexadecene and eicosane in D.Q. A time
series in D20 was conducted to measure the relative rates of deuterium incorporation
for an alkadiene, an alkene and an alkane. The gas chromatograms for the aliphatic
fractions are shown in Fig. 3.14. Hydrogenation of this fraction produced only
alkanes (Fig. 3.15). The patterns of deuterium incorporation for the three
hydrocarbons for each experiment are shown in Figs. 3.16 to 3.20.
Low density polyethylene pyrolysis. Pyrolysis experiments investigating the
aqueous organic hydrothermal chemistry was extended to include low density
polyethylene (LDPE), a highly cross-linked aliphatic polymer. This polymer was
chosen since its structure resembles the chemically resistant aliphatic biopolymer
material of kerogen thought to be the most important precursor of -a1kanes in crude
oils (Burlingame et al., 1969; Simoneit and Burlingame, 1973; Goth et al., 1988;
Tegelaar et al., 1989a,b,c). Hydrous pyrolysis of LDPE was performed under alkaline
conditions to inhibit the secondary acid-catalyzed reactions of the alkene pyrolysis
products. No gas pressure was detected at the termination of the reaction. Fig. 3.2la
is the gas chromatogram of the aliphatic fraction. The products are dominated by
homologous series of terminal -a1kenes and -alkanes ranging from C10 to C37,
maximizing at C16. The absence of any appreciable amount of ethylene is due to the
predominance of thermal degradation reactions of the aliphatic polymer network
rather than depolymerization reactions. This distribution of pyrolysis products
resembles the product distributions from flash pyrolysis experiments of LDPE
67
(Sugimura and Tsuge, 1978). Catalytic hydrogenation of this fraction is shown in Fig.
3.21b, showing a smooth, homologous series of -alkanes almost indistinguishable
from distributions found in the -C32H66 pyrolyses or any highly aliphatic oil. The
results from this experiment indicate that hydrous pyrolysis of LDPE produces
alkanes and terminal ii-alkenes as primary cracking products, with a small amount of
branched hydrocarbons formed.
Pyrolysis of 1.1 3-tetradecadiene polymerization product. Polymerization of
1,13-tetradecadiene occurred during a 330°C pyrolysis experiment with D20, the first
72 hr pyrolysis experiment done in the small reaction vessels. The polymer lined the
walls of the reaction vessel but was easily removed without breakage. It was a thin,
flexible, translucent polymer. It is likely that the interior of the vessel was
catalytically active and aided in the polymerization of the a,o-olefin into presumably
an aliphatic and highly cross-linked polymer. A portion of the polymer was pyrolyzed
under identical time and temperature conditions with H20 as the medium. The results
of the pyrolysis experiment are shown in Fig. 3.22. The m/z 99 mass fragmentogram,
characteristic of n-alkanes, shows that the major pyrolysis products of the
C14
polymer are -alkanes.
The previous pyrolysis experiments with fl-C32H66 and aliphatic polymers
have demonstrated that hydrous pyrolysis of aliphatic material produces -alkanes and
terminal n-alkenes. Secondary reactions of the alkenes (i.e. bond isomerization
reactions) can rapidly introduce protons (or deuterons) from the water (or heavy
water) into the hydrocarbons. To test whether this is a feasible chemical pathway for
the deuterium incorporation observed in the original Hoering (1984) pyrolyses of
Messel shale with D20, the pyrolysis was repeated under the same time and
temperature conditions. Since only saturated hydrocarbons were observed in the
original pyrolyses, time series experiments were run to determine the relative rates of
alkene isomerization versus alkene hydrogenation and deutenum incorporation.
Messel shale pyrolysis repeat of Hoerin (1984) experiment. The Messel
shale D20 pyrolysis experiments of Hoering (1984) were repeated using the Parr
reaction vessel and the stainless steel reaction pipes. The extent of deuterium
incorporation into the 11-alkanes was measured and there was no difference in the
extent of deuterium substitution from the Parr reaction vessel or the pipe reactors. The
deuterium substitution for the C17 to C29 n-alkanes is shown in Table 3.2. Shown in
Fig. 3.23 is an unweighted average of the C17 to C29 -alkane deuterium substitution
distribution. Comparing these results to the original Hoering distribution shown in
Fig. 3.1, there is a difference in the distribution of deuterium substitution, primarily in
the DO to D3 range. These results suggest that there was a much smaller amount of nalkanes formed in the DO to D3 range than in the experiment performed by Hoering
(1984). But in general a very large amount of deuterium incorporation has occurred in
the -alkanes that were generated in the heating experiments.
Messel shale H20 pyrolyses
composition of aliphatic molecular probes.
Two time series experiments were performed involving Messel shale in the pipe
reaction vessels. The first series in H20 was conducted to measure the relative rates
of alkene isomerization versus hydrogenation for an alkadiene and an alkene when
pyrolyzed in the presence of Messel shale. The gas chromatograms for the aliphatic
fractions are shown in Fig. 3.24. Hydrogenation of this fraction produced alkanes and
a minor amount of branched/cyclic compounds (Fig. 3.25). Data from this series are
found in Table 3.3 and show that the rate of acid-catalyzed alkene isomerization is
much faster than the rate of hydrogenation.
Messel shale DO pyrolyses - composition of aliphatic molecular probes. The
second time series was conducted in D20 to measure the relative rates of alkene
isomerization and deuterium incorporation for an alkadiene, an alkene and an alkane
when pyrolyzed in the presence of Messel shale. The gas chromatograms for the
aliphatic fractions are shown in Fig. 3.26. Hydrogenation of this fraction produced
alkanes (Fig. 3.27).
The patterns of deuterium incorporation for the three
hydrocarbons for each experiment are shown in Figs. 3.28 to 3.32, and data from this
series are summarized in Table 3.4. This series has shown that the rate of acidcatalyzed alkene isomerization is slightly slower in D20 than in H20. Deuterium was
incorporated in the saturated alkane, interpreted as being due exclusively to a radical
exchange process, but the degree of deuterium incorporation in the saturated
hydrocarbon is much slower than in either of the olefin species.
Messel shale H70 and D,O pyrolyses composition of aliphatic hydrocarbons
released from kerogen. Additional information about the process of hydrous pyrolysis
was obtained in the time series experiments by looking at the -alkanes and
triterpenoid hydrocarbons released from the Messel shale kerogen. Fig. 3.33 shows
the range of pyrolysis products starting at ll-C23H48 to ll-C32H66. Fig. 3.34 shows the
GC traces of the 1, 5, and 10 hr experiments at higher concentrations. After 1 hr a
homologous series of terminal -alkenes and -alkanes are generated from the kerogen
in an approximate ratio of 1:2. The 5 and 10 hr experiments shows evidence of alkene
isomerization and a decrease in the alkene to alkane ratio. Alkenes were not detected
in either the 36 or the 72 hr reactions.
Free alkenes were also detected in the triterpenoid hydrocarbons released from
the kerogen. Fig. 3.35 is the mlz 191 mass fragmentograms characteristic of the
thterpenoid hydrocarbons released in the Messel shale H20 time series experiments.
After 1 hr the dominant compounds in the mlz 191 fragmentogram are the hopenes.
The mass spectra of the hopenes indicate that the points of unsaturation all occur in
the D or E rings of the C29 and C30 hopanes, and in the alkyl side chains of the
hopanes C31 or greater. This is consistent with being bound to the kerogen at this end
of the pentacyclic structure. The hopenes are were not detected after 10 hr. These
triterpenoid biomarker distributions show the progression from an thermally immature
distribution to one characteristic of the earliest stages of oil generation. After 10 hr
there is not much change in the biomarker pattern, the only obvious trends are the
progressive change in the Is / Tm ratio and the slight isomerization of the C31a(R)
hopane to the C31c4(S).
Fig. 3.36 is the m/z 191 mass fragmentogram showing the triterpenoid
hydrocarbons released in the Messel shale after 72 hr in D20. Selected mass spectra
of the major hopanes are presented in Fig. 3.37. These mass spectra confirm that the
deuterium incorporation has occurred in the D and E rings or the side chains of the
hopane structures. The most likely explanation for these substitution patterns is
deuterium incorporation has occurred by both isomerization and during the process of
saturating the double bond. A homogeneous radical exchange process would produce
a random deuterium distribution pattern in all rings of the pentacyclic structure, which
would be distinguishable from the mass spectra.
Guaymas Basin sediment D,O pyrolysis - composition of aliphatic molecular
probes. One 10 hr experiment was performed where the three aliphatic probes were
spiked on a sediment from the Guaymas Basin hydrothermal system. The deuterium
substitution patterns for the three molecular probes are shown in Fig. 3.38. No
deuterium was incorporated in the saturated eicosane but a large amount of deuterium
was incorporated in the alkenes. These deuterium substitution patterns are unique in
that they show that extensive deuterium incorporation has occurred in those alkenes
that have isomerized. This suggests that there is a strong catalytic effect associated
with the sediments which promotes extensive double bond isomerization once the
alkenes begin to isomerize.
70
Elemental sulfur D20 pyrolysis composition of aliphatic molecular probes.
One 10 hr experiment was performed where the three aliphatic probes were combined
with 0.5 g elemental sulfur. The deuterium substitution patterns for the three
molecular probes are shown in Fig. 3.39. Although this was only a 10 hr experiment,
extensive deuteration occurred, even in the saturated alkane. This set of results
demonstrates the large degree to which sulfur can greatly accelerate both the ionic and
radical exchange processes.
The procedure of laboratory hydrous pyrolysis is one method used to study the
transformations of sedimentary organic matter and source rocks to petroleum. These
experiments are performed over short durations but at elevated temperatures to
compensate for the lower temperature organic reactions which occur over geological
time scales. The presence of water is generally regarded as an important component
of pyrolysis simulations by generating aliphatic-rich pyrolysates which are very low or
absent in olefins, as opposed to the olefin rich pyrolysates formed by dry pyrolyses
(Lewan et al., 1979). Ever since Lewan and co-workers (1979) used water in their
experiments and named the procedure hydrous pyrolysis, the actual role of water has
been a point of controversy, especially when oil-like pyrolysates have been formed
under anhydrous conditions (Comet et al., 1986). But it has been shown that in
general under aqueous conditions, these pyrolysates resemble natural oils (Eglinton et
al., 1986; Eglinton and Douglas, 1988; Lewan, 1983; Lewan et al., 1986). Water also
has the important ability of facilitating the ionic mineral reactions which are primarily
responsible for fixing the Eh and pH of a system (Eugster, 1986; Shock, 1990).
Although Lewan and co-workers (1979) have shown that water does not increase the
amount of hydrogen to the organic material, hydrogen exchange between water and
hydrocarbons can occur.
The original D20 pyrolysis experiments performed by Hoering (1984)
identified the extent to which deuterium from the D20 is exchanged with organic
matter and incorporated into the aliphatic hydrocarbons generated under hydrous
pyrolysis conditions for 72 hr at 330°C. By using D20 as a medium instead of H20,
insight into what role water plays in this simulated maturation process was obtained.
But the free radical mechanism proposed does not explain the degree to which the
deuterium is incorporated (Ross, 1992a,b). The experiments performed by Hoering
were duplicated in this study and additional experiments were performed with H20
and D20.
71
In the present series of experiments the major types of chemical reactions and
their relative rates leading to the pyrolysate distributions of aliphatic material have
been identified. During hydrous pyrolysis the primary products generated by the
thermally-induced bond cleavages of the aliphatic components are -a1kanes and
terminal n-alkenes, the same products generated during the Curie-point pyrolyses of
hydrocarbons and aliphatic-rich materials (Tegelaar et al., I 989a,b,c). The terminal n-
alkenes can undergo secondary isomerization and hydrogenation reactions. The
relative rates of the primary and the two competing secondary reactions depend on the
experimental conditions. Thermal destruction of the aliphatic kerogen network should
also produce double bonds in the kerogen which can undergo isomenzation reactions
by which deuterium is directly incorporated into the kerogen network.
Fig. 3.40 shows the proposed chemical pathways by which fl-C32H66 reacts in
the presence of H20 and H20 NaOH. Fig. 3.41 presents the analogous reactions
when performed in D20, showing the pathway in which deuterium is incorporated into
the aliphatic hydrocarbon by acid-catalyzed double bond isomerization. When two
double bonds are present, as in the molecular probe experiments in D20 involving
1,1 3-tetradecadiene, acid-catalyzed double bond isomerization occurs simultaneously
to greatly accelerate the amount of deuterium incorporated into the hydrocarbon (Fig.
3.42).
When these molecular probes were pyrolyzed on a sediment from the Guaymas
Basin, a deuterium distribution pattern resulted which did not resemble those for
samples pyrolyzed in water only. This distribution is interpreted to have resulted from
the catalyzed isomerization by the clay minerals present in the sediments. Those
alkenes which were isomerized were extensively isomerized and incorporated a large
amount of deuterium (Fig. 3.43). There was still a large amount of alkene that was not
isomerized.
A proposed pathway for the generation of -a1kanes and terminal -alkenes
during the hydrous pyrolysis of LDPE is shown in Fig. 3.44. This pathway was
proposed since primarily -alkanes and terminal -alkenes are generated, and no
appreciable amounts of a,-alkadienes were observed. The weakest bonds of an
aliphatic cross-linked polymer such as LDPE are at the branch points, where there is a
tertiary carbon. Thermal homolytic bond dissociation at one of these branch points is
shown in Fig. 3.44. A hydrogen abstraction by the released primary radical results in
the formation of an -alkane with a secondary radical somewhere in the polymer
network. The secondary radicals in the polymeric network, formed by the bond
72
scissions or H-abstractions, would then undergo 3-scission, breaking the aliphatic
cross-link to form an alkane chain and a terminal alkene chain still bonded to the
polymer. With the weakest links still being the tertiary carbons, bond breaking at the
branch points would still be favored and the process would continue, resulting in
alkanes and terminal -alkenes. The gas chromatograms of the LDPE pyrolysis in
Fig. 3.21 show the production of other pyrolysis products, presumably branched
hydrocarbons, but these were minor products and most likely the result of other
competing radical cracking or isomerization reactions. Compared to Curie-point
pyrolysis, the pyrolysis temperatures used in this study are comparatively milder and
therefore bond cleavages can be more selective, preferentially breaking at branch
points. Curie-point pyrolyses of LDPE (Wampler and Levy, 1987; Wampler, 1989)
and aliphatic-rich kerogen (Goth et al., 1988) produce three homologous series,
alkanes, terminal p.-alkenes and a,w-alkadienes, indicating a more random thermal
destructive process breaking secondary and tertiary carbon-carbon bonds.
The proposed chemical pathway for the hydrous pyrolysis of LDPE can be
used to explain the extent of deuterium incorporation observed in the D20 Messel
shale pyrolyses. The resulting pyrolysate compositions are interpreted to be due to
radical cracking of the polymethylene chains from the kerogen. The carbon carbon
bond scission produces free -alkanes and terminal n-alkenes, but also saturated and
terminally unsaturated alkyl chains still bound to the kerogen. Acid-catalyzed double
bond isomerization of the double bonds occurs at a rate faster than hydrogenation of
the double bond (Fig. 3.24), and when the pyrolysis experiment is performed in D20,
deuterium can be rapidly incorporated into the aliphatic hydrocarbons and
polymethylene kerogen network. Once the alkyl chain is hydrogenated, it is relatively
unreactive and deuterium incorporation occurs by radical exchange, a chemical
pathway where the rate of exchange is much slower (Figs. 3.28 3.32).
The results suggest that the primary mode of deuterium incorporation into
hydrocarbons occurs during acid-catalyzed double bond isomerization of alkene
intermediates by 1,2-shifts of carbocations. Radicals would not be expected to
undergo 11,2-shifts because in the rearranging radical, one electron must go into the
antibonding orbital in the three-centered transition state, and therefore the transition
state would be destabilized (Wilt, 1973). The formation of intermediate branched and
isoprenoid alkenes, terminal n-alkenes, and even cL,w-alkadienes from kerogen is
consistent with the findings from the structure elucidations of kerogens by chemical
methods. Carboxylic acids, branched carboxylic acids, a,o-dicarboxylic acids, and
73
isoprenoid acids are common products from kerogen oxidations (Burlingame et al.,
1969; Djuricic et al., 1971; Simoneit and Burlingame, 1973; Vitorovic, 1980). Since
branching points are susceptible to oxidation, monocarboxylic acids and isoprenoid
acids would be formed from alkyl groups and isoprenoid groups, respectively,
attached to the kerogen matrix at one point. a,oDicarboxylic acids would be formed
as a result of an alkyl "bridge" which is attached to the kerogen at two points. Curiepoint pyrolysis confirms that this highly aliphatic polymer is present in Messel shale
kerogen (Goth et al., 1988). The conditions during hydrous pyrolysis experiments
may cause similar fragments, but release primarily 11-alkanes and terminal -alkene
groups, analogous to the proposed pathway for the thermal destruction of LDPE under
hydrous pyrolysis conditions. These double bonds, in the free pyrolysates and the
bound aliphatic network, would then undergo acid-catalyzed double bond
isomerization prior to hydrogenation of the double bond. Fig. 3.45 is a sequence of
reactions which shows the proposed primary mode of deuterium incorporation into
hydrocarbons during Messel shale pyrolysis with D20.
Water is seen as a medium in which the rate at which the inorganic ionic
reactions occur is accelerated relative to dry pyrolysis. The system is driven more
rapidly to equilibrium in the presence of water. Under these temperature and pressure
conditions, water is also a good solvent for organic molecules. When hydrous
pyrolysis is performed with reduced minerals (i.e. reduced sulfur species) the whole
system can quickly become reducing, favoring the hydrogenation of unsaturated
hydrocarbons. But this hydrogenation process is most likely a surface process, similar
to the process of catalytic hydrogenation. So even under reducing conditions, as in the
pyrolyses of Messel shale where iron sulfides are present, the hydrogenation of nalkenes becomes a diffusion limited reaction, and the rate of acid-catalyzed double
bond isomerization can be much faster than the rate of hydrogenation. The balance of
competing radical and ionic reactions is important when trying to simulate geological
processes under greatly accelerated laboratory conditions.
74
CONCLUSIONS
The pyrolysis of Messel shale in D20 generates hydrocarbons with a large
amount of deuterium. The exchange process is explained by double bond
isomerization of alkenes formed by the pyrolytic breakdown of the aliphatic kerogen
network. The major points are:
(1)
deuterium exchange between D20 and saturated alkanes is negligible
relative to the exchange which occurs by acid-catalyzed isomerization
of a double bond under the same conditions,
(2)
the extent of deuterium substitution during the Messel shale D20
pyrolysis experiment can be explained by acid-catalyzed double bond
isomerization of intermediate alkene species,
(3)
the preferential deuterium enrichment at one end of a molecule would
result from deuterium exchange at the site of one double bond,
(4)
the formation of alkene species has been observed during the hydrous
pyrolysis of Messel shale,
(5)
the formation of intermediate ailcene species is consistent with the
results from the structural elucidations of kerogens by chemical
oxidation, Curie-point pyrolysis experiments and hydrous pyrolysis of
hydrocarbons and synthetic polymers under various conditions.
This mechanism explains the amount of deuterium incorporation into alkanes
during Messel shale pyrolyses with D20 and explains how deuterium can become
enriched at one end of a molecule. By studying simple systems, relevant chemical
pathways can be proposed and applied to the understanding of more complex systems.
75
Table 3.1. Hydrous pyrolysis experiments performed at 330°C.
Duration (hr)
Reactants
72
D20, n-C37H66
72
D20, n-C32H66, NaOD
72
H20, LDPE
D20, 1,1 3-tetradecadiene
H20, C14 polymer
Messel Shale, D20
D20, 1 ,13-tetradecadiene, I -hexadecene, eicosane
D20, 1,1 3-tetradecadiene, I -hexadecene, eicosane
D20, 1,1 3-tetradecadiene, I -hexadecene, eicosane
D20, 1,1 3-tetradecadiene, 1 -hexadecene, eicosane
D20, 1,1 3-tetradecadiene, 1 -hexadecene, eicosane
Messel Shale, H20, 1,1 3-tetradecadiene, I -hexadecene, eicosane
Messel Shale, H20, 1,1 3-tetradecadiene, I -hexadecene, eicosane
Messel Shale, H20, 1,1 3-tetradecadiene, I -hexadecene, eicosane
Messel Shale, H20, 1,1 3-tetradecadiene, I -hexadecene, eicosane
Messel Shale, H20, 1 ,l3-tetradecadiene, 1-hexadecene, eicosane
Messel Shale, D20, 1,1 3-tetradecadiene, I -hexadecene, eicosane
Messel Shale, D20, 1,1 3-tetradecadiene, I -hexadecene, eicosane
Messel Shale, D20, I .1 3-tetradecadiene, 1 -hexadecene, eicosane
Messel Shale, D20, 1,13-tetradecadiene, 1-hexadecene, eicosane
Messel Shale, D20, 1,1 3-tetradecadiene, 1 -hexadecene, eicosane
Guaymas Basin Sediment, D20, 1,1 3-tetradecadiene,
72
72
72
I
5
10
36
72
1
5
10
36
72
1
5
10
36
72
10
1 -hexadecene, eicosane
10
Sulfur, D20, 1,1 3-tetradecadiene, 1 -hexadecene, eicosane
L1
Table 3.2. Extent of deuterium substitution in normal hydrocarbons produced from
the pyrolysis of Messel shale at 3 30°C for 72 hr with D20.
Carbon Number
Deuterium
Abundance
DO
Dl
D2
D3
D4
D5
D6
D7
D8
D9
D10
Dli
D12
D13
D14
D15
D16
D17
D18
D19
D20
D21
D22
17
18
19
10214
30
54
84
87
100
92
89
86
79
72
59
42
37
16
11
8
7
8
2
0
0
0
28
53 49
68 76
96 82
99
100
100 89
97 92
95 53
73 74
68 76
64 62
56 33
54 71
31
38
27 31
12
20
41
15
11
6
9
7
4
0
0
8
0
0
0
20
21
22
23
24
25
26
27
28
29
7
6
5
4
55
5
18
8
27
46
75
85
100
99
85
95
3
10
7
27
45
68
82
86
100
6
17
5
25
65
82
96
100
87
87
88
74
70
49
39
47
34
27
19
10
91
70
80
62
55
44
39
25
22
81
69
58
42
45
25
25
14
4
10
12
7
2
3
5
0
0
0
0
0
0
3
12
26
27
100 83
66 78
66 89
68 100
59 92
54 85
50 76
39 71
32 63
36 53
22 49
15
24
14
9
4
10
0
10
100
0
0
0
0
0
0
26
37
46
52
78
47
99 67
93 79
94 93 84
98 96 100 100
94 81 79 91
100 90 89 88
83
100 53
81
73 78 81
66
54 60 50 75
65 49 48 43
52 49 44 60
40 36 27 22
25 19 23
19
10 31
19
15
15
19
10
15
4
8
9
6
4
3
9
9
0
0
0
3
0
0
0
0
83
48
83
108
106
0
0
0
14
31
128
11
25
34
52
62
54
100
79
62
66
52
32
43
37
18
12
10
12
3
6
0
0
77
Table 3.3.
Data from the pyrolysis of 1,13-tetradecadiene and 1-hexadecene
molecular probes with Messel in H20 at 330°C.
1,1 3-tetradecadiene
Time (hr)
% Isomerized % Hydrogenated
I -hexadecene
% Isomerized
% Hydrogenated
1
12.6
0
5.7
0
5
89.9
11.6
70
22.2
10
96.2
13.6
84.8
33
36
97.2
50.5
91.9
65.8
72
100
94
100
96
Table 3.4.
Data from the pyrolysis of 1,13-tetradecadiene and 1-hexadecene
molecular probes with Messel in D20 at 330°C.
1,1 3-tetradecadiene
Time (hr)
% Isomerized
% Hydrogenated
9.9
0
5.5
0
0
45.1
13.6
10
74.4
85.3
33.1
58.7
25.6
36
n.d.
a
67
n.d.
a
71
72
n.d.
a
88.3
n.d.
a
87.9
1
5
a
% Isomerized % Hydrogenated
1 -hexadecene
Not determined due to poor chromatographic peak shape as a result of deuterium
substitution.
79
100
Messel Shale + D20
C17 to C29 n-Alkanes
72 hr @ 330 C
90
80
(Hoering,
u 70
1984)
260
50
.4o
30
20
10
0
0
1
2
3
4
5
6
7
8
9
tO
11
12
13
14
Deuterium Substitution
Figure 3.1. Overall average distribution of deuterium substitution in -a1kanes from
C17 to C29 generated from the D20 pyrolysis of Messel shale (after Hoering, 1984).
100
90
80
70
60
50
.
40
30
20
10
0
183
184
185
186
187
188
189
190
191
192
193
194
195
196
m/z
Figure 3.2. Distribution of the relative abundances of C13 ion fragments from pristane
generated in the Messel shale D20 pyrolysis (after Hoering, 1984).
E31
250
125
200
210
220
230
240
250
260
mie
Figure 3.3. The partial mass spectrum of deuterated 2-methyiheptadecane which was
generated in the Messel shale D20 pyrolysis (Hoering, 1984).
100
Octadecane + D20
+ Messel Shale
72 hr @ 330 C
(Hoering, 1984)
90
80
u 70
260
50
.
40
30
20
10
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Deuterium Substitution
100
1-Octadecene + D20
+ Messel Shale
72 hr @ 330 C
(Hoering, 1984)
90
80
70
260
50
.40
30
20
10
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Deuterium Substitution
Figure 3.4. Distribution of deuterium substitution in the products of the molecular
probe experiments, 330°C for 72 h : (a) pyrolysis of docosane and D20 and (b)
pyrolysis of 1 -octadecene and D20 (after Hoering, 1984).
H + DO±D. + HDO.
Olefin formation and
chain propagation
Primary radical
HHH
HHH
RCCC
RC---C = CH + H
HHH
H
HHH
HHH
RCC = CH + D'+ RC----C--CD + H
HH
H
HHH
HHH
RCCCD RC = CCD + H
H
F!
H
HHH
HHH
H
DH
RC = CCD ± D RC--C----CD
HHH
HHH
CC--CD + D--C--CCD or 2DD-,
DH
DDH
Chain termination
Figure 3.5. Set of reactions proposed by Hoering (1984) to explain the deuterium
exchange process, includes only free radical chemistry.
Initiation
kerogen - RC11CH2CH2R
Propagation
D20+PhOH
HOD +PhOD
RC11CH2CH2R + PhOD RCHDCH2CH2---R + PhO
PhO + RCHDCH2CH2R - RCHDCH2C11R + PhOH
RCHDCH2C11R + PhOD etc.
Figure 3.6. Set of reactions proposed by Ross (1992a) to explain the deuterium
exchange process, includes ionic and free radical chemistry.
n-alkanes
J1tJIii_LU_JUiiJUUiuJ
b)
J1[jjjjjjj.
jLjjjjJiJjJjfljjjfljijc)
a
0
I
jr_i-.?
= terminal n-alkenes
JJIiIJJjiJ
I I
H20-n-C32H66-HCI
d)
J_Le)
H20-n-C32H66--NH4CI
H2O--C32H66-Na2SO4
fl_i
UJJJJ.iJJJiiJftftuJLL
0
i
H20
n-C32H66- Sulfur
32
16
3
g)
15
17
19
21
23
I L1i I J IHI
h) H2OnC32H66- Sulfide
Time
Figure 3.7. Gas chromatograms of the total extracts from the hydrous pyrolysis
experiments of -C32H66 at 350°C: (a) H20 n-C32H66;( b) H20
NaC1;
(c) H20 n-C32H66 HC1;( d)H20 n-C32H66 - NaOH;( e)H20 n-C32H66 NH4C1;
(f) H20 -C32H66- Na2SO4; (g) H20 fl.-C32H66- Sulfur;( h) H20 fl-C32H66Sulfide. Numbers refer to carbon chain lengths of -alkanes.
a
lonpolar Fraction
16
1517
14
T
19
11 1
32!
21
23
Hydrogenated
Nonpolar Fraction
.25
13
¶.29
'1
J
Time
Figure 3.8. Gas chromatograms of the H20 -C32H66 system: (a) nonpolar fraction
before catalytic hydrogenation; (b) nonpolar fraction after catalytic hydrogenation.
Numbers refer to carbon chain lengths of -alkanes.
87
e
Ikanes
inal n-alkenes
Nonpolar Fraction
15
4
b)
2
16
32
17
Hydrogenated
Nonpolar Fraction
19
21
23
,1H
I r?l?.
34
Time -?-
Figure 3.9. Gas chromatograms of the H20 n-C32H6ó NaOH system: (a) nonpolar
fraction before catalytic hydrogenation; (b) nonpo'ar fraction after catalytic
hydrogenation. Numbers refer to carbon chain lengths of -alkanes.
n-alkanes
16
32
.
24
20
28
.
.
.
iH I
12
l
I
I
1.1
Nonpolar Fraction
.
.
b)
..
1iiiiItJi11.
c)
.
.
.
Alkane Fraction
fl
Alkene Fraction
d)
.
Jill
I
I
I
I
I
I
I
I
I
I
I
I
Time
I
I
I
III j.
I
I
II
II.
Hydrogenated
Alkene Fraction
)-
Figure 3.10. Gas chromatograms of the D20 jj-C32H66 system :( a) nonpolar
fraction; (b) alkane fraction; (c) alkene fraction; (d) alkene fraction after catalytic
hydrogenation. Numbers refer to carbon chain lengths of -alkanes.
a)
X
20
108.0
50.0
113
12?
te
K/E
141
150
250
208
XSO
b)
180.8
50.8
113
ti/E
50
lee
127
141
150
288
Figure 3.11. Mass spectra of fl-C17H36 from the D20 fraction; (b) hydrogenated alkene fraction.
258
-C32H66 system
:( a) alkane
90
= n-alkanes
0=
terminal n-alkenes
32
.
16
.
r
0
0
.
20
0 00.oj.24
e4?
0
-.
I.
I!
28
Nonpolar Fraction
.
)fl
.
I
.
.
.
I
Alkane Fraction
II
.
.iii
ro
Alkene Fraction
cJ=oo
.
I
ML
Time
I
'
.
Hydrogenated
Alkene Fraction
-)-
Figure 3.12. Gas chromatograms of the D20 12-C32H66 NaOD system :( a)
nonpolar fraction; (b) alkane fraction; (c) alkene fraction; (d) alkene fraction after
catalytic hydrogenation. Numbers refer to chain lengths of -alkanes.
91
x 20
188.0
7
58.0
113 127
M/E
so
141
tee
155 169
150
288
250
b)
x 20
180.0
58.8
113 127
M'E
$8
tee
141
155 169
150
288
250
Figure 3.13. Mass spectra of -Ci 7H36 from the D20 - fl-C32H66 -NaOD system (a)
alkane fraction; (b) hydrogenated alkene fraction.
92
C2,
Cl
!_t
I
Figure 3.14. Gas chromatograms of the aliphatic fraction from the pyrolyses of 1,13tetradecadiene, 1 -hexadecene and eicosane with D20 at 330°C: (a) 1 hr; (b) 5 hr; (c)
10 hr; (d) 36 hr; (e) 72 hr. I.S. = internal standard (C24D50).
Cq
C14.
C)
d
Figure 3.15. Gas chromatograms of the hydrogenated aliphatic fraction from the
pyrolyses of 1,1 3-tetradecadiene, 1 -hexadecene and eicosane with D20 at 330°C: (a) I
hr; (b) 5 hr; (c) 10 hr; (d) 36 hr; (e) 72 hr.
c..) 100
90
v 80
.
1,13-Tetradecadiene + D20
1 hr @ 330 C
70
60
50
-
40
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9DIODIIDI2DI3DI4DI5DI6DI7DISDI9D2OD2ID22
Deuterium Substitution
b) 100
1-Hexadecene + D20
1 hr @ 330 C
90
80
n 70
60
50
.40
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2D13DI4DI5DI6DI7D1SDI9D2OD2ID22
Deuterium Substitution
100
Elcosane + D20
1 hr @ 330 C
90
80
70
60
50
40
C.)
30
20
10
0
DO DI D2 D3 D4 D5 D6 D7 D8 D9DIODI1DI2DI3DI4D15DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.16. Histograms showing the extent of deuterium substitution after pyrolysis
in D20 for 1 hr at 330°C: (a) 1,1 3-tetradecadiene; (b) 1 -hexadecane; (c) eicosane.
95
o.) 100
90
80
1,13-Tetradecadiene + D20
5 hr @ 330 C
70
60
50
40
.
.30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DISDI9D2OD2ID22
Deuterium Substitution
h) 100
1-Hexadecene + D20
5 hr @ 330 C
90
80
70
260
50
40
.
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 D1ODIIDI2DI3DI4DI5DI6DI7DISDI9D2OD2ID22
Deuterium Substitution
c) 100
Eicosane + D20
5 hr @ 330 C
90
80
70
260
50
C?
.
40
.30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 D10D11D12D13D14D15D16D17D18D19D20D21D22
Deuterium Substitution
Figure 3.17. Histograms showing the extent of deuterium substitution after pyrolysis
in D20 for 5 hr at 330°C: (a) 1,1 3-tetradecadiene; (b) 1 -hexadecane; (c) eicosane.
c)100
90
1,13-Tetradecadiene + D20
10 hr @ 330 C
80
u 70
60
50
40
.30
20
10
0
DO DI D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DISDI9D2OD2ID22
Deuterium Substitution
bD 100
1-Hexadecene + D20
10 hr @ 330 C
90
80
70
60
50
40
30
20
10
0
DO DI D2 D3 D4 D5 D6 D7 D8 D9 DIODI1DI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
100
Eicosane + D20
10 hr @ 330 C
90
80
u 70
.60.
50
.
40
.30.
20
100
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.18. Histograms showing the extent of deuterium substitution after pyrolysis
in D20 for 10 hr at 330°C: (a) 1,13-tetradecadiene; (b) 1-hexadecane; (c) eicosane.
97
100
1,13-Tetradecadiene + D20
36 hr @ 330 C
90
80
70
60
50
.
40
30
20
10
0
DO
DI D2 D3 D4 D5 D6 D7 D8 D9 D10D11D12D13D14D15D16D17D18D19D20D21D22
Deuterium Substitution
100
D20
36 hr @ 330 C
1-Hexadecene
90
80
70
60
50
.
40
-30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 DIODI1DI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
c) 100
+ D20
36 hr @ 330 C
Eicosane
90
80
70
60
50
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 DO DIODIIDI2DI3DI4D15DI6DI7DISDI9D2OD2ID22
Deuterium Substitution
Figure 3.19. Histograms showing the extent of deuterium substitution after pyrolysis
in D20 for 36 hr at 330°C: (a) 1,1 3-tetradecadiene; (b) I -hexadecane; (c) eicosane.
100
90
1,13-Tetradecadiene + D20
72 hr @ 330 C
80
70
60
50
.
40
.30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
,
0)
100
1-Hexadecene + D20
72 hr @ 330 C
90
80
70
260
50
.
40
3O
20
10
0
DO DI D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DISDI9D2OD2ID22
Deuterium Substitution
c) 100
Eicosane + D20
90
72 hr
80
330 C
u 70
260
50
.
40
.30
20
10
0
DO DI D2 D3 D4 D5 1)6 1)7 D8 1)9 DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.20. Histograms showing the extent of deuterium substitution after pyrolysis
in D20 for 72 hr at 330°C: (a) 1,1 3-tetradecadiene; (b) 1 -hexadecane; (c) eicosane.
b)
I'
.7
.2
I
'=I
I
i..
20
I
I
21
28
I
I
I
I
'8
I
I
I
I
III
I
Figure 3.21. Gas chromatograms from the pyrolysis of LDPE in H20 for 72 hr @
330°C: (a) aliphatic fraction; (b) hydrogenated aliphatic fraction. Numbers refer to
carbon chain lengths of -a1kanes.
100
10
1OO.-
-
,,
.
Figure 3.22. Mass fragmentogram mlz 99, representative of -alkanes, for the
pyrolysis of the C14 polymer. Numbers refer to carbon chain lengths of 11-alkanes.
101
100
Messel Shale + D20
72 hr 330C
90
C?
C)
SO
70
60
50
V
40
C)
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.23. Overall average distribution of deuterium substitution in -alkanes from
Cy' to C29 generated from the D20 pyrolysis of Messel shale (this research).
102
C.2
dc
T. 'S.
b)
c2
;.çc-c
c)fl
II
C.1.
II
C,'
C20
s)
C,14
CIA.
e)
i
JL_ _ _.A_ _ I
Figure 3.24. Gas chromatograms of the aliphatic fraction from the pyrolyses of 1,13tetradecadiene, I -hexadecene and eicosane spiked on Messel shale in H20 at 330°C:
(a) I hr; (b) 5 hr; (c) 10 hr; (d) 36 hr; (e) 72 hr. I.S. = internal standard (C24D50).
103
I
dJL
Figure 3.25. Gas chromatograms of the hydrogenated aliphatic fraction from the
pyrolyses of 1,1 3-tetradecadiene, I -hexadecene and eicosane spiked on Messel shale
in H20 at 330°C: (a) 1 hr; (b) 5 hr; (c) 10 hr; (d) 36 hr; (e) 72 hr. I.S. = internal
standard (C24D50).
104
JL
d)
Figure 3.26. Gas chromatograms of the aliphatic fraction from the pyrolyses of 1,13tetradecadiene, 1 -hexadecene and eicosane spiked on Messel shale in D20 at 330°C:
(a) 1 hr; (b) 5 hr; (c) 10 hr; (d) 36 hr; (e) 72 hr. I.S. = internal standard (C24D50).
105
7. s-.
=
c)
d)
J
Figure 3.27. Gas chromatograms of the hydrogenated aliphatic fraction from the
pyrolyses of 1,1 3-tetradecadiene, I -hexadecene and eicosane spiked on Messel shale
in D20 at 330°C: (a) 1 hr; (b) 5 hr; (c) 10 hr; (d) 36 hr; (e) 72 hr. I.S. internal
standard (C24D50).
106
c.)
100
1,13-Tetradecadiene + D20
90
+ Messel Shale
330 C
1 hr
80
70
60
50
40
.
30
20
10
0
DO DI D2 D3 D4 D5 1)6 D7 D8 D9DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD21D22
Deuterium Substitution
100
I,)
cJ
1-Hexadecene + D20
+ Messel Shale
1 hr @ 330 C
90
80
70
60
50
V
40
V
30
20
10
0
DO Dl D2 D3 D4 D5 1)6 D7 D8 D9DIODIIDI2DI3DI4DI5DI6DI7DISD19D2OD2ID22
Deuterium Substitution
100
Eicosane + D20
+ Messel Shale
1 hr @ 330 C
90
80
-
70
60
50
V
.
40
-30
20
10
0
DO DI D2 D3 1)4 D5 1)6 D7 D8 D9DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.28. Histograms showing the extent of deuterium substitution after pyrolysis
on Messel shale in D20 for 1 hr at 330°C: (a) 1,13-tetradecadiene; (b) 1-hexadecane;
(c) eicosane.
107
c)
100
1,13-Tetradecadiene + D20
90
Q
+ Messel Shale
5 hr @ 330 C
80
70
60
50
40
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
b)
100
1-Hexadecene + D20
+ Messel Shale
5 hr @ 330 C
90
80
u 70
60
50
.
40
3O
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 DO DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
c)
100
Eicosane + D20
+ Messel Shale
5 hr @ 330 C
90
80
=
70
60
50
.
40
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 DO DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.29. Histograms showing the extent of deuterium substitution after pyrolysis
on Messel shale in D20 for 5 hr at 330°C: (a) 1,1 3-tetradecadiene; (b) 1 -hexadecane;
(c) eicosane.
100
1,13-Tetradecadiene + D20
90
+ Messel Shale
10 hr @ 330 C
80
70
6O
50
40
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
1-Hexadecene + D20
90
+ Messel Shale
10 hr @ 330 C
80
u 70
.60
50
.
40
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
100
Eicosane + D20
+ Messel Shale
10 hr @ 330 C
90
80
70
60
50
30
20
10
0
DO Dl D2 D3 D4 D5 1)6 D7 1)8 D9 DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.30. Histograms showing the extent of deuterium substitution after pyrolysis
on Messel shale in D20 for 10 hr at 330°C: (a) 1,1 3-tetradecadiene; (b) 1 -hexadecane;
(c) eicosane.
109
100
1,13-Tetradecadiene + D20
90
+ Messel Shale
36 hr @ 330 C
80
70
60
50
.
40
.30
20
10
0
DO DI D2 D3 D4 D5 D6 D7 D8 D9 D1ODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
b)
100
1-Hexadecene + D20
90
+ Messel Shale
36 hr @ 330 C
80
70
60
50
40
30
20
10
[II
DO DI D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
c)
100
Eicosane + D20
+ Messel Shale
36 hr @ 330 C
90
80
70
60
50
.
40
30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.31. Histograms showing the extent of deuterium substitution after pyrolysis
on Messel shale in D20 for 36 hr at 330°C: (a) 1,1 3-tetradecadiene; (b) 1 -hexadecane;
(c) eicosane.
c)
100
1,13-Tetradecadiene + D20
90
+ Messel Shale
72 hr @ 330 C
80
70
60
50
.
40
.3O
20
10
0
DO DI D2 D3 D4 D5 D6 D7 D8 D9 DIODI1DI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
100
1-Hexadecene + D20
+ Messel Shale
72 hr @ 330 C
90
80
70
60
50
.
40
30
20
10
0
DO DI D2 D3 D4 D5 D6 D7 D8 D9 D10D11D12D13D14D15D16D17D18D19D20D21D22
Deuterium Substitution
tOO
Eicosane + D20
+ Messel Shale
72 hr @ 330 C
90
80
70
60
50
40
30
20
10
0
DO DI D2 D3 D4 D5 1)6 D7 D8 D9 DIODIIDI2DI3DI4DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.32. Histograms showing the extent of deuterium substitution after pyrolysis
on Messel shale in D20 for 72 hr at 330°C: (a) 1 .1 3-tetradecadiene; (b) I -hexadecane;
(c) eicosane.
111
1LL
)1flJjJLJJ
2$
iffli[i.L
2
ej
Figure 3.33. Gas chromatograms for the pyrolysis products released from the Messel
shale kerogen during the pyrolyses in H20 at 330°C: (a) I hr; (b) 5 hr; (c) 10 hr; (d) 36
hr; (e) 72 hr. Numbers refer to carbon chain lengths of -alkanes. I.S. = internal
standard (n-C32D66).
112
.5-
c
,-_
,--
17
S
22.
A'
.1
01
2
I
el
OJ
I
c)
Figure 3.34. Gas chromatograms for the pyrolysis products released from the Messel
shale kerogen during the pyrolyses in H20 at 330°C: (a) I hr; (b) 5 hr; (c) 10 hr. Same
samples as in Fig. 3.33 but concentration increased to show components in lower
concentration. Numbers refer to carbon chain lengths of -alkanes. I.S. = internal
standard (ll-C32D66).
113
j,p_S'7l2l) -e.c
/L
191
C32
T
151JLiL_______
C;
c)
)
c2rx
0
151.
4)
c3r.,cc
C29.(5
151
C.prp
_JLJjirii
e)
CZ1t9c
c0c
C2o(3
,,
191 -
c
C(3 C31
-I__s
808
988
1188
1888
1288
1388
Scan
Figure 3.35. Mass fragmentogram mlz 191 representing triterpenoid hydrocarbons
released from the Messel shale kerogen during the pyrolyses in H20 at 33O°C-(a) 1
hr; (b) 5 hr; (c) 10 hr; (d) 36 hr; (e) 72 hr.
114
cl'i(3
Ii
/a1
(I
ii
1s
T
I
h
I
.1.
I
)
11
it
,
Figure 3.36. Mass fragmentogram mlz 191 representing triterpenoid hydrocarbons
released from the Messel shale kerogen during the pyrolyses in D20 for 72 hr at
330°C.
115
8.8
2.8
lEO
18
2ê8
150
250
320
358
88.8
1
P1'E
50
iéo
158
288
258
300
358
158
288
250
300
358
.88.8
52.8
18
I;
r/E
50
100
Figure 3.37. Selected mass spectra of polydeuterated triterpenoid hydrocarbons
generated in the D20 pyrolysis of Messel shale for 72 hr at 330°C.
116
100
1,13-Tetradecadiene + D20
+ Guaymas Basin Sediment
10 hr @ 330 C
C;:.)
90
80
70
60
50
40
.
3O
20
10
0
DO
Dl D2 D3 D4 D5 D6 D7 D8 D9 D10D11D12D13D14D15D16D17D18D19D20D21D22
Deuterium Substitution
100
90
+
80
1-Hexadecene + D20
Guaymas Basin Sediment
10 hr @ 330 C
70
260
50
.:40
30
20
10
0
DO
Dl D2 D3 D4 D5 D6 D7 D8 D9 D10D11D12D13D14D15D16D17D18D19D20D21D22
Deuterium Substitution
c)
100
Eicosane + D20
Guaymas Basin Sediment
10 hr 330 C
90
80
70
260
50
.:
40
.30
20
10
0
DO Dl D2 D3 D4 D5 D6 D7 D8 D9 DIODIIDI2DI3D14DI5DI6DI7DI8DI9D2OD2ID22
Deuterium Substitution
Figure 3.38. Histograms showing the extent of deuterium substitution after pyrolysis
of molecular probes on Guaymas Basin sediment in D20 for 10 hr at 330°C: (a) 1,13tetradecadiene; (b) 1 -hexadecane; (c) eicosane.
117
100
90
so
-
1,13-Tetradecadiene + D20
+ Elemental Sulfur
10 hr @ 330 C
70
60
50
40
.
30
20
l0
0
'C r- 00
C - r'
0' C -
'0 v
'C
r'
00
0'
-
'0
'C
C - (4 N r'
N
r-
00
0' C -
'0
r
C'
Deuterium Substitution
100'
1-Hexadecene + D20
+ Elemental Sulfur
10 hr @ 330 C
90'
80
70
-
60
50
0)
40
.
.30
20
10
0
C - C'l
, '0V
'C'
r- 00
0' 0 -
'0
'C
N
00
00 0 C - N
0
- C
N N N N '0
N N 'C
N N
N N
N
.
'0
.
r
Deuterium Substitution
00
Eicosane + D20
+ Elemental Sulfur
10 hr @ 330 C
90
80
70
60
50
0)
.:
40
30
20
10
0
o - N
'0
0 N
N..
C N 00 0' 0 N ..'0 V '0 N 000'
N N
N '0
N N '0
N NNN000'
N .. 0 N c'0
Deuterium Substitution
Figure 3.39. Histograms showing the extent of deuterium substitution after pyrolysis
of molecular probes with 0.50 g elemental sulfur in D20 for 10 hr at 330°C: (a) 1,13tetradecadiene; (b) 1 -hexadecane; (c) eicosane.
118
/
-a1kane
\adical C-C bond breaking
ct-olefin
I
no ionic
reactions
H catalyzed double
bond isomerization
internal olefin
Figure 3.40. Set of proposed reactions showing a simplified version of the major
primary and secondary reactions occurring during the pyrolysis of -C32H66 in H20.
119
-C32H66
/
-a1kane
no ionic
reactions
ica1 C-C bond breaking
a-olefin
D catalyzed double
bond isomerization
internal olefin (partially deuterated)
Figure 3.41. Set of proposed reactions showing a simplified version of the major
primary and secondary reactions occurring during the pyrolysis of fl-C32H66 in D20.
120
4
14
I-;
-'
I
j4
!-
)
I
I
I
14
l4
14
H
I
I
c=c:--C-
/
14
1-4
c--- a-C- -c C
I
I
I
1-1
LL
II-
1-4
LI
t
N
4-
'T
c-c-c: --C-C--c-c-c:--c---c-CD
cCC CC--- CCc CC-- CC- C:
4Z)
c
C- C
C-c-C -C-c-CC-C-
I
r)
$
\L
\ui
I-c'
4 del)
Figure 3.42. Set of proposed reactions showing a simplified version of the deuterium
exchange reactions occurring during the pyrolysis of 1,1 3-tetradecadiene in D20.
121
cI
/
..
4-
-4--
0
7)
el :.-
.f-
1)
C
N
I
C - C
6
-C- C-c - C- cc c c
C
t
(_
-
K
-C.
'
K
(1_.:
I
Figure 3.43. Set of proposed reactions showing a simplified version of the deuterium
exchange reactions occurring during the pyrolysis of 1,1 3-tetradecadiene in D20
spiked on Guaymas Basin sediments.
122
C
L-O
\
C
C
C
C
,2_aL
7''i" c
C
C
4-.,
c_C.0
psI.1..0
'Nc3 -
-C
--' .p
C
-
._
//
C
/j:c
'e.
C
\od.c
,
ci'ee
Set of proposed reactions showing a simplified version of the thermal
breakdown of LDPE under hydrous pyrolysis conditions.
Figure
3.44.
123
I
L.
-
c
í - '
ie,L
J
7
2-;
5
-
\ if
\
1)
II
c.,_/
\.
-1l)
,-_
,.
(1) ..cL94-)
Figure 3.45. Proposed reaction pathway for the thermal alteration and deuterium
exchange processes occurring during the D20 pyrolysis of Messel shale.
124
CHAPTER 4
Simulation of Thermally-Enhanced Diagenetic and Catagenetic
Transformations of Organic Matter in Surface Sediments from the
Southern Trough of Guaymas Basin
125
ABSTRACT
In a preliminary study to simulate the hydrothermal petroleum generation
process, a series of hydrous pyrolysis experiments (24 hr at 200, 250, 300 and 350°C)
was conducted using a thermally unaltered sediment from Guaymas Basin, Gulf of
California. The volatile hydrocarbons and bitumen were analyzed to monitor the
changes in the compositions as a function of thermal stress. Some diagenetic and
catagenetic alterations of organic matter observed in near surface sediments of the
Guaymas Basin hydrothermal system have been duplicated by these short duration
hydrous pyrolysis experiments.
The production of typical thermogenic hydrocarbons was accompanied by the
production of an unusually large amount of volatile alkenes, with the proportion of
alkenes to alkanes decreasing with temperature. Significant -a1kane generation only
occurred in the 350°C experiment. A progressive change was observed in the Carbon
Preference Index (CPI) from 6.42 in the unaltered sediment to 1.4 in the 350°C
experiment. Diploptene (hop-22(29)-ene) was the major component of the triterpenoid
hydrocarbons of the unaltered sediment. In the 200°C experiment diploptene
disappeared and hop-17(21)-ene became the major component of the triterpenoid series.
The 250°C and 300°C experiments resulted in an overall decrease of the triterpenes, but
there was the appearance of C27 to C32 hopanes (C28 missing) and the emergence of the
C32 benzohopane with a minor amount of C33 benzohopane. The benzohopanes were
not detected in the 350°C experiment, where the triterpenoid distribution was dominated
by a13- and 13a-hopanes. The overall polycyclic aromatic hydrocarbon (PAH)
distribution was similar to a thermally immature sediment. Perylene dominated and its
concentration increased from 52 ng/mg bitumen in the unaltered sediment to 117 nglmg
bitumen in the 300°C experiment. Significant destruction of perylene occurred in the
350°C experiment. Diels' hydrocarbon, a C18 compound in the short-alkyl-chain series
of triaromatic steroid hydrocarbons and a proposed indicator of rapid hydrothermal
petroleum generation processes, was generated during the 250°C and higher
expenments.
The biomarker transformations and PAH distributions in this series of
experiments are more representative of hydrothermally-enhanced diagenesis, indicating
that higher temperatures andlor longer heating durations are necessary to generate the
types of petroleum products found in the Guaymas Basin hydrothermal system.
126
INTRODUCTION
The Guaymas Basin, Gulf of California is an actively spreading basin formed by
the diverging Pacific and North America plates. The rift zones in the basin are
distinguished from most spreading centers by having a thick sediment cover of
diatomaceous oozes and mud turbidites. Petroleum generation occurs primarily by dike
and sill intrusions into these sediments (Einsele et al., 1980; Lonsdale, 1985; Simoneit,
1983). 14C ages for selected petroleum samples range from 3200 to 6600 years B. P.
(Peter et al., 1991; Simoneit and Kvenvolden, 1993) indicating a significant amount of
contemporary organic detritus has been converted to petroleum. Hydrothermal
petroleums sourced from such recent sediments are characteristically enriched in poiar
constituents with a high polycyclic aromatic hydrocarbon (PAH) content (Simoneit,
1984; Simoneit et al., 1992a; Kawka and Simoneit, 1990). The quick, high temperature
hydrothermal petroleum generation process is well suited for studying by laboratory
methods such as hydrous pyrolysis, a closed system pyrolysis technique where the
organic source material is kept submerged under water for the duration of the heating
experiment (Lewan et al., 1979). This procedure was adapted in an attempt to simulate
the hydrothermal petroleum generation process. The pyrolysates formed in the heating
experiments were analyzed and the results were compared to oils and naturally-altered
sediment extracts taken from the Guaymas Basin hydrothermal system.
127
EXPERIMENTAL
Samples. Fig. 4.1 a is a map showing the Guaymas Basin trough system located
in the Gulf of California. Fig. 4.1 b is an enlargement of the Southern Trough of
Guaymas Basin. The surface sediment sample used in the experiments came from site
PC-i of the Southern Trough of Guaymas Basin. Also shown is the location of the
comparison core, PC-6, an 8 meter piston core which sampled a hydrothermally altered
sediment (Simoneit et al., 1992b).
The water depths at these locations are
approximately 2000 m.
Hydrous pyrolysis experiments. The piston core PC-i sampled an area not
affected by hydrothermal activity. The surface sediment recovered with this core was
transferred to a Naigene® bottle and immediately frozen. Prior to the heating
experiments the whole sediment was thawed, homogenized and split into 25g portions.
These fractions were placed in the freezer until needed for the hydrous pyrolysis
experiments.
A 250 mL T3 16 stainless steel pressure vessel (Parr Instrument Co. ) with gage
block designed for hydrothermal studies to 600°C and 6000 psig (408 bar) was used in
the heating experiments. The reaction vessel and thawed sediment sample was placed in
a glove bag and flushed with five volumes of N2. The sediment was transferred to the
reaction vessel and water was added to result in a water to sediment ratio of 3 to 1. The
vessel was sealed and placed in a heater, temperature was controlled to ± 3°C. The
temperatures used for the experiments ranged from 150° to 3 50°C at 50°C intervals and
pressures from 290 to 2400 psig (20 to 163 bar). Each experiment lasted 24 hrs.
Extraction and fractionation. The reaction vessel was removed from the heater
and cooled to room temperature upon completion of the heating cycle. The volume of
gas generated from each heating experiment was measured and a sample was stored in a
gas tight vial until analysis by gas chromatography. The pyrolyzed sediments were
extracted with three 25 mL portions of methanol followed by five 50 mL portions of
methylene chloride. All the solvent extracts were combined with the water from the
pyrolysis experiment in a separatory funnel and the organic fraction collected. The
water was extracted with two additional portions of methylene chloride and the two
methylene chloride fractions were combined. The methylene chloride was dried with
anhydrous sodium sulfate and the solvent was removed using a rotary evaporator at
30°C. The total extract was made up to 2 mL of methylene chloride.
128
The total extract (2 mL) was deasphalted using 100 mL of heptane. The
asphaltenes were allowed to precipitate overnight and removed by filtration. The
deasphalted fractions were fractionated on a column (30 cm x 1 cm) packed with 3.8 g
alumina (fully active) over 3.8 g silica gel (fully active). Each sample was separated
into three fractions by elution with 50 mL heptane (nonpolar, Fl), 50 mL toluene
(aromatic, F2) and 25 mL methanol (polar , F3).
Gas chromatography. The gas chromatography (GC) of the volatile
hydrocarbons was performed with a Shimadzu GC-mini 3 equipped with a 1.8 m x
0.22 cm i.d. packed column (Poropak Q 50/80 mesh). The GC oven was heated using
the following program: initial temperature 40°C, programmed to 180°C at 10°C/mm.,
and isothermal at 180°C for 16 mm., with the injector and detector at 225°C, and helium
as the carrier gas. The GC of the sediment extracts was performed with a Hewlett
Packard 5890A equipped with a 30 m x 0.25 mm i.d. DB-5 open tubular column (0.25
jim film thickness). The GC oven was heated using the following program: isothermal
for 2 mm. at 65°C, 4°/mm. to 3 10°C, and isothermal for 30 mm., with the injector at
290°C, detector at 325°C, and helium as the carrier gas.
Gas chromatography-mass spectrometry. The gas chromatography-mass
spectrometry (GC-MS) was performed on a Finnigan 9610 gas chromatograph coupled
to a Finnigan 4021 quadrupole mass spectrometer operated at 70 eV over the mass range
50-650 dalton and a cycly time of 2.0 s. The GC oven temperature was programmed at
isothermal for 2 mm. at 65°C, 3°/mm. to 310°C, and isothermal for 30 mm., with the
injector at 290°C, and helium as the carrier gas. The MS data were processed with an
on-line Finnigan-Incos 2300 computer data system.
129
RESULTS AND DISCUSSION
Volatile hydrocarbons. The gas chromatograms of the volatile hydrocarbons are
shown in Fig. 4.2, and quantitative data and selected ratios are shown in Table 4.1.
The production of typical thermogenic volatile hydrocarbons was confirmed by the low
values (<50) of the C11(C2 + C3) molar ratios (Bernard et al., 1976; Simoneit et al.,
1988). But the heating experiments also produced an unusually large amount of volatile
alkenes in addition to the standard distribution of thermogenic volatile alkanes.
Although the amounts of all the volatile hydrocarbons increased with increasing
temperature, the proportion of volatile alkenes to volatile alkanes decreased as
temperature increased. This is demonstrated by the steady drop in the ethylene to ethane
ratio (C2:i/C2) from 6.0 in the 200°C experiment to 0.3 in the 350°C experiment.
n-Alkanes. The gas chromatograms of the total extracts are shown in Fig. 4.3.
Large amounts of low molecular weight compounds were generated in the 200, 250 and
300°C experiments, but no significant -alkane generation was observed. A major
change was observed in the 350°C experiment where the -alkanes were some of the
most abundant components in the total extract.
Fig. 4.4 shows the mass
fragmentograms (m/z 99) representing the -a1kane distribution. Heating of the recent
sediment resulted in the conversion of the -alkane distribution from a terrestrial nalkane signature to one more representative of an oil. The carbon preference index
(CPI) progressively decreased from 6.4 in the unaltered sediment to 1.4 in the 350°C
experiment. The -a1kanes in the unaltered sediment ranged from C15 to C37 with a
carbon number maximum (Cmax) at C29, and a strong odd/even carbon number
predominance (>C23) characteristic of a significant terrestrial input (Brassell et al.,
1978). Little change was observed for the 200 and 250°C experiments. The 300°C
experiment resulted in a bimodal distribution ranging from C15 to C39 with a Cmax =
C29 and a minor maximum at C21. The 3 50°C experiment resulted in a more uniform n-
alkane distribution ranging from
C13
to C33 maximizing at
C19.
Triterpenoid hydrocarbons. The distributions of the triterpenoid biomarkers are
shown in Fig. 4.5 with biomarker concentrations listed in Table 4.2. The triterpenoid
biomarker transformations can be characterized as thermally-enhanced diagenetic
reactions in the lower temperature experiments to early catagenetic reactions in the
350°C experiment. The triterpenoid distribution of the unaltered sediment was
characteristic of the Recent sediments from Guaymas Basin where hop-22(29)-ene
(diploptene) is the major component (Simoneit et al., 1979). But diploptene could not
130
be detected in the extracts of the pyrolysis experiments. The loss of diploptene in the
200°C experiment was accompanied by a corresponding increase in hop- 17(21 )-ene
suggesting a near quantitative conversion of diploptene to hop- 17(21 )-ene, which has
been proposed as a diagenetic transformation (Ensminger, 1977; Venkatesan, 1988a).
The distribution of the triterpenoid biomarkers in the 200, 250 and 300°C experiments
consisted of those compounds characteristic of diagenetic transformations. There was
an overall decrease in the triterpenes with the concomitant appearance of the C27 to C32
17f(H),213(H)-hopanes (C28 missing) and emergence of the C32 and C33
benzohopanes. The 17(H),21a(H)-hopanes and 17a.(H),213(H)-hopanes were formed
in the 300 and 350°C experiments. The C-22 SI(SR) epimer ratio of 1 7a(H),2 1 (H)-
homohopane of 0.12 in the 300°C experiment and 0.32 in the 350°C experiment
indicated a minimum of thermal stress, i.e., incomplete maturation. The benzohopanes
were not detected in the 350°C experiment.
Polycyclic Aromatic Hydrocarbons. The concentrations of the major polycyclic
aromatic hydrocarbons (PAH) are shown in Fig. 4.6. The major PAH in the unaltered
sediment was perylene. The compound perylene, which is primarily diagenetic in origin
(Louda and Baker, 1984; Venkatesan, 1 988b), increased in concentration in the 200,
250 and 300°C experiments suggesting an additional production of perylene by heating.
Low levels of pyrolytic PAH common in oils and sediment extracts of Guaymas Basin
were also generated. The 350°C experiment resulted in the destruction of perylene with
the further increase in the pyrolytic PAH. A comparison of these PAH distributions to
Guaymas Basin oils and sediment extracts previously analyzed reveals that the 200 to
300°C experiments generated PAH which are very similar to thermally immature
sediments, but the 350°C experiment resulted in a distribution more characteristic to
sediments that have been altered by dolerite sill intrusions (Kawka, 1990; Kawka and
Simoneit, 1990).
Diels' hydrocarbon. Fig. 4.7 are the mass fragmentograms of m!z 217 and m/z
231 showing the relative distributions of two series of triaromatic steroid hydrocarbons
in the unaltered sediment and the heating experiments. Diels' hydrocarbon, a triaromatic
steroid hydrocarbon common in Guaymas Basin petroleum and a proposed tracer of
hydrothermally derived oils, was generated in the 250°C and higher temperature
experiments. Fig. 4.7 shows the generation of Diels' hydrocarbon and the concomitant
loss of the other long-chain steroid hydrocarbons, indicating that a possible
transformation to Diels' hydrocarbon is occurring from these compounds. The
concentration of Diels' hydrocarbon is shown in Fig. 4.6 relative to the polycyclic
131
aromatic hydrocarbons, showing that this tnaromatic steroid hydrocarbon is comparable
in concentration to the other PAH generated in the heating experiments.
Ketones. A survey of oils from the Guaymas Basin has revealed several
homologous series of alkanones that are ubiquitous in the poiar NSO fractions. The
alkan-2-ones are usually in highest concentration, followed by 3-, 4-, 5- (and higher)
isomers. An examination of the NSO fractions from these heating experiments detected
the alkanones only in the 350°C experiment. Their pyrolytic origin was verified by the
smooth homolog distribution, but the ketones were primarily the -alkan-2-one isomers.
The ketone mass fragmentogram is shown in Fig. 4.8.
These preliminary hydrous pyrolysis experiments resulted in a variety of
thermally-enhanced diagenetic reactions and early catagenetic reactions. The time I
temperature relationships were such that catagenetic reactions leading to hydrothermal
petroleum were minimal in the 200, 250 and 300°C experiments but enhanced in the
350°C experiment. The major chemical processes with the aliphatic components
observed in the heating experiments, cracking and isomerization, can be explained by a
combination of radical and ionic mechanisms.
The volatile hydrocarbons generated in the heating experiments had a high
proportion of alkenes, but the degree of unsaturation decreased with increasing reaction
temperature. Volatile alkenes, especially ethylene, are common products formed from
the thermal cleavage of aliphatic hydrocarbons by a radical cracking mechanism
(Tsuchiya and Sumi, 1968). But alkenes are not present in the high temperature vent
fluids of the Guaymas Basin (Simoneit, 1983b; Simoneit et al., 1988), although low
levels of alkenes of biological origin have been detected in the interstitial gases of
Guaymas Basin sediments (Whelan and Hunt, 1982). The large amount of volatile
alkenes generated in the heating experiments is interpreted as primary cracking products
that have not undergone hydrogenation. Instead they have partitioned into the
headspace of the bomb and away from the catalytic surfaces which facilitate double
bond reduction. Under these operating conditions, the headspace of the reaction vessel
appears to affect the rates of these secondary hydrogenation reactions. A large excess of
water along with the presence of a gas headspace in the reaction vessel may decrease
those reaction rates that are influenced by mineral surface chemical reactions.
Another type of reactions likely to be affected by the partitioning away from the
minerals and into the gas or liquid phases would be isomerization reactions, where the
rates of these reactions have been found to be greatly influenced by the type of minerals
present (Huizinga et al., 1987a,b; Kissin, 1987, 1990; Lu et al., 1989; Peters et al.,
132
1990). This may explain why decreased catalytic activity is observed when organicmineral pyrolysis experiments are performed with an excess of water (Henderson et al.,
1968; Eisma and Jurg, 1969; Huizinga et al., 1987a,b). Monthioux and co-workers
(1985) have suggested that the most natural catagenetic conditions are better simulated in
the laboratory by using closed-system experiments with a reduced free volume, and a
minimum of any diluting gas.
Very little change in the -a1kane distribution occurred in the 200°C and 250°C
experiments. But greater -alkane formation from the C16 to C27 range commenced in
the 300°C experiment, with a large amount of -a1kane generation in the 350°C
experiment. Alkenes were not found in the bitumen from these heating experiments,
suggesting that the hydrogenation reactions have occurred to sufficiently reduce the
alkenes of the cracking products.
The changes observed in the hopanoid biomarkers ranged from the diagenetic
diploptene to hop- 17(21 )-ene conversion, most likely occurring by an acid catalyzed
isomerization, to early catagenesis (e.g. epimerization of the C31a hopane). The
biomarker changes observed in these heating experiments parallel the biomarker
transformations observed in the lower sections of core PC-6 (Fig. 4.9), an eight meter
long piston core which sampled a hydrothermally altered sediment column in the vicinity
of active hydrothermal mounds of the Southern Trough of Guaymas Basin (Simoneit et
al., 1992b).
The total extracts in the 200, 250 and 300°C experiments contained a large
amount of low molecular weight polar compounds. This may be due to the fact that the
pyrolysis bomb, being a closed system, cannot duplicate some of the natural
hydrothermal processes such as solubilization and porewater transport or water-washing
which likely affect the relative proportions of the aliphatic, aromatic and polar NSO
compounds. Therefore certain constituents which may normally be transported away by
porewater fluid migration are retained in the total extract.
133
CONCLUSIONS
The results obtained in these heating experiments show that the hydrous
pyrolysis experiments can alter the surficial sediments similarly to some of the near
surface reactions occuning naturally in Guaymas Basin. These reactions are a
combination of radical and ionic mechanisms. It is likely that under these hydrous
pyrolysis conditions, the primary pathway of releasing aliphatic components from the
kerogen is by radical cracking. But secondary reactions, such as isomerizations and
epimerizations, are most likely ionic reactions. Secondary radical reactions, such as
double bond hydrogenation, are likely surface mediated and therefore may become
diffusion controlled in large reactions vessels. Care should be taken when extrapolating
the results of heating experiments performed in batch reactors with large amounts of
excess water and large headspaces. Organic components typically remain in contact
with mineral surfaces during natural sedimentary hydrothermal alteration. But in this
experimental design, the pyrolysates can quickly be partitioned away from the mineral
surfaces and remain in the gas and liquid phases.
This study simulated some of the reactions which occur during the earliest stages
of hydrothermal petroleum generation. The overall process of hydrothermal petroleum
generation likely occurs over a wide temperature range (warm to> 350°C).
134
Table 4.1. Analytical results of volatile hydrocarbon analyses for 24 hr heating
experiments.
Temp.
Gas Yield
(°C)
mL@STP (ppm)
C1
C2:i
(ppm)
C2
C3
C3:i
(ppm) (ppm)
C1_
c2:1
(ppm)
(C2+C3)
C2
25.Ob
6.0
3.8
0.9
0.3
200
39
450
108
18
77
250
67
1180
426
112
380
n.d.a
n.d.a
300
80
5760
1030
1060
1310
695
3.3
350
126
37750
1965
5720
2700
2925
4.4
a not determined due to poor resolution
b this ratio represents a maximum value due to lack of C3 data
10.5b
135
Table 4.2. Triterpenoid concentrations from the 24 hr heating experiments (nglg sed.)
Compound
Unaltered
200°C
250°C
l's
Tm
23
26
13
C29a3
Hop-17(21)-ene
43
467
C293a
36
C9
165
33
39
68
189
43
10
53
127
39
112
10
43
16
23
18
67
164
32
-
4
29
55
87
-
27
68
-
-
C31ct13(S)
C31a13(R)
Hop-22(29)-ene
-
66
C3I3a
C3o133
37
95
-
-
480
-
-
-
C32a(S)
C32a
C32 Benzohopane
C33 Benzohopane
66
12
C32a13(R)
C31
350°C
74
C3oc43
Neohop-13(18)-ene
300°C
-
50
13
29
12
40
-
83
40
47
11
7
16
42
88
78
-
5
14
-
136
IU°26W
a)
"
1
b)04N1-'
I
'' Sciton
250
24W
22W
I
Trough
V'
30°N
LAL
25°
711
27°
/
EAST PACIFIC
RISE 21°N
HYDROTHERMAL
.'7\
FIELD
/
--
0
-
I
km
J..-. PATCHES OF
HYDROThERMAL
SINTER AND MOUNDS
,
20°
115°W
110°
Figure 4.1. (a) Map of Gulf of California showing geographic location of the sampling
area, and (b) Southern trough of Guaymas Basin.
137
C
C
C0
0
0O
C)
I
1)
C
lime
Figure 4.2. Gas chromatograms of volatile hydrocarbons: a) 24 hr @ 200°C; b) 24 hr
@ 250°C; c) 24 hr @ 300°C; d) 24 hr @ 350°C.
138
Unaltered
b)
24 h @ 200°C
C)
o
p.(
t
C)
24 h @ 250°C
0
o
0
a
24h@ 300°C
e)
n-Alkanes
24h@ 350°C
e
2' i; 2
Time
Figure 4.3. Gas chromatograms of the total extracts: a) Unaltered; b) 24 hr @ 200°C;
c) 24 hr @ 250°C; d) 24 hr @ 300°C;- e) 24 hr @ 350°C. Numbers refer to carbon
chain lengths of-a1kanes.
139
29
31
i
',)
27
m/z 99
Unaltered
23252j281301
19 2211
i 1,JI
,i
.
3435
32
I
.
29
31
I
27
m/z 99
24 h @ 200°C
25
32
21
23 23 24
I
4)
c,
33
C
3
29
rn/z99
24h@ 250°C
0)
19
20 21 22 23
25
4)
d)
23
21
19
20
m/z 99
I,
i
28
26
18
17
16.
I
i
I
I
I
I
33
32335
I
I
1
1
I
I
24h@300°C
13637
19
17
120
18
15
16
t
I
I
I
I
m/z 99
24 h@ 350°C
14
I
16:48
33:20
50:88
I
I
I
66:40
323
83:28
Time
Figure 4.4. Mass fragmentograms of m/z 99, characteristic of n-alkanes: a) Unaltered;
b) 24 hr @ 200°C; c) 24 hr @ 250°C; d) 24 hr @
refer to carbon chain lengths of -a1kanes.
300°C;
e) 24 hr @ 350°C. Numbers
ct.)
m/z
191
Unaltered
b)
m/z
0
191
24h.@ 200°C
cJ
C3
Imhz 191
C3i6
Nethop-13(IS).aie
Ic
/
.11
-c3czI
I
i
c32pj
ç33BazthopaDe
d)
m/z
191
300°C
e)
c31Q
mhz 191
24h@ 350°C
C3j
c3
I-
I
66:40
70:88
73:20
76:40
80:00
Time
Figure 4.5.
Mass fragmentograms of mlz 191, characteristic of triterpenoid
hydrocarbons: a) Unaltered ; b) 24 hr @ 200°C; c) 24 hr @ 250°C; d) 24 hr @ 300°C;
e) 24 hr @ 350°C. Concentrations of components are listed in Table 4.2.
0
'1
0
o
(
r
1
(-
1
-
CD
CD
CD
><
0
.
H
,-
-
c)
0
Fluorene
Diets' HC
Dibenz(a,c)pyrene
Coronene
Renzo(g,h,i)peiylene
Anthanthrene
Dibenz(a,h)anthracene
Perylene
Benz(a)pyrene
I3cnz(c)pyrene
J3enzofluoranthenes
ChrysenelFriphenylene
enz(a)anthracene
2,3-Benzofluorene
Pyrene
Fluoranthene
Anthracene
Dibenzothiophene
Phenanthrene
0
(-S
C
Ui
§
0
C
C
(
C
Ui
t')
Concentration (ng/g dry sediment)
(S
C
C
t)
(
CD
142
1
Diels' Hydrocarbon not detected
2171
Unaltered
m/z231
I
m/z 217
Diels' Hydrocarbon not detected
II 24 h
200°C
m/z 231
1
C
c)
25R VS
DHC
mlz 217
2Ss-
-'-4
24h
250°C
24 h
300°C
24h
350°C
I.
,5
m/z231
DHC
d)
m/z217
m/z231
DI1C
e)
2i7S4, -
m/z 217
1
231 S
c91l1
m/z 231 1 ©$P
1
.:48
58:6
53:2
56:46
8:8
63:28
66:46
?:66
?3:2OTIE
Figure 4.7. Mass fragmentograms of two series of triaromatic steroid hydrocarbons
(m!z 217 and mlz 231): a) Unaltered ; b) 24 hr @ 200°C; c) 24 hr @ 250°C; d) 24 hr @
300°C; e) 24 hr @ 350°C. Concentrations of Diels' hydrocarbon relative to polycyclic
aromatic hydrocarbons are shown in Fig. 4.6.
143
lee.
'5'-7
'4
I
''
,Z
I
'a
2.3
I
z.o
2.2.
f
2.'I
508
1888
1588
2808
2588
Scan
Figure 4.8. Mass fragmentogram (mk 57, 58, 71, 72) representative of -ketones
present in the 350°C heating experiment.
Laboratory Hydrous Pyrolysis
Hydrothermatly Altered Sediment
PC-I
PC-6
24 h @ 200°C
392-397 cm
LAj4cT
NØohop-13(18)-ene
Ca
d)
C3ou
C29a
Ncobop-13(18)-ac
L4h@350C
-
C29
C3O
793-795 cm
j(R)
C32x
,c
(R)
jRR)
66:48
78:08
Time
73:28
66:40
78:08
73:28
Time
Figure 4.9. Mass fragmentograms m/z 191 representative of triterpenoid hydrocarbons:
a) PC-i, 24 hr @ 200°C; b) PC-6, 392-397 cm below sea floor; c) PC-i, 24 hr @
350°C; d) PC-6, 793-795 cm below sea floor. Distributions for heating experiments
and PC-6 showing parallel transformations in the heating experiments and the naturally
altered sediment.
145
CHAPTER 5
Simulation of Hydrothermal Catagenetic Transformations of Organic Matter in
Surface and Downcore Sediments from the Northern Trough of Guaymas Basin
ABSTRACT
A series of pyrolysis experiments, using one surface sediment and two
downcore sediments from the Northern Trough of Guaymas Basin, Gulf of California,
was conducted to study the effects of time during the laboratory simulated
hydrothermal catagenetic alteration of sedimentary organic matter. These experiments
were conducted using a modified pyrolysis technique which eliminates the headspace
and excess water inside the reaction vessel. Each sediment was pyrolyzed at 330°C
for 24, 48 and 72 hr. The extent of alteration was measured by monitoring the
alkanes, acyclic isoprenoids, steroid and tnterpenoid biomarkers, polycyclic aromatic
hydrocarbons, ketones and isoprenoid phenols. The experimental results were
compared to sediment extracts which have been naturally altered by sill intrusion and
accompanied hydrothermal fluid flow.
Smooth -a1kane patterns were generated with all sediments after 24 hr and
full hopane and sterane maturation in 48 hr. The mature hopane ratios were altered by
unequal destruction of the hopanes. The polycyclic aromatic hydrocarbons were
progressively converted from a perylene- to phenanthrene-dominated pattern in the
deepest sediment, and Diels' hydrocarbon was major in the upper and surface
sediments. Ketones were present in the NSO fractions of all experiments.
The experimental pyrolysis experiments duplicate the natural hydrothermal
alteration which has occurred by dolerite sill intrusions in the Guaymas Basin
sediments. The results indicate that the extent of steroid diagenesis may be the most
important factor in the formation of Diels' hydrocarbon. These experiments support
the hypothesis that aliphatic ketones are common products under pyrolytic conditions.
147
INTRODUCTION
The production of petroleum hydrocarbons under marine hydrothermal
conditions is a well documented process (Simoneit, 1988, 1990 and references within).
The sedimentary organic matter associated with the Guaymas Basin hydrothermal
system is pyrolyzed by the high thermal gradient of a heat source at depth and by dike
and sill intrusions into the unconsolidated sediments. On Leg 64 of the DSDP drilling
program, sediments from the Guaymas Basin rift system were sampled and several
sills were identified which have been emplaced at different depths below the sea floor.
The characteristics of these hydrothermally generated oils associated with the
intrusions depends on the heating duration, heating temperature and nature of the
source organic matter. The depths at which these sills were emplaced generated oils
from sedimentary organic matter that had undergone different extents of diagenesis.
A set of seabed oils has been analyzed by radiochemical dating procedures and
indicated that these oils have been generated from a carbon pooi that is approximately
5000 years old (Peter et al., 1991). This was a broad, random selection of oils
associated with the hydrothermal vents. This data indicates that most of the
hydrothermal oils presently emanating from the vents are derived from relatively
shallow marine sediments. The present study was a simulation of this hydrothermal
generation process by laboratory pyrolyses of whole sediments from different depth
horizons, and a comparison was made with the results of sediments that have been
altered by a massive sill intrusion. The objective was to determine how sedimentary
organic matter from different depth horizons affected the quality of the generated oils.
Experimental data on catagenetic conversions of sedimentary organic matter
and petroleum source rocks have been obtained from a variety of high temperature
experiments employing different experimental designs. These experiments have been
performed in open or closed systems, different times, temperatures, dry or wet
conditions, using diverse starting materials, sometimes with associated or added
minerals. The experiments have demonstrated how time, temperature, minerals and
pressure influence the organic matter conversions under the particular experimental
conditions (Horsfield, 1984 and references within).
The presence of water is generally regarded as an important component of
pyrolysis simulations, although ever since Lewan and co-workers (1979) used water in
their experiments and named the procedure hydrous pyrolysis, the actual role of water
has been a point of controversy, especially when oil-like pyrolysates have been formed
148
under anhydrous conditions (Comet et al., 1986). But it has been shown that under
aqueous conditions, these pyrolysates resemble natural oils (Eglinton et al., 1986;
Eglinton and Douglas, 1988; Lewan, 1983; Lewan et al., 1986). Water also has the
important ability of facilitating the ionic mineral reactions which are primarily
responsible for fixing the Eh and pH of a system (Eugster, 1986; Shock, 1990).
Therefore the presence of water appears to be essential when simulation of the natural
environment is desired.
In conventional hydrous pyrolysis experiments, many grams of rock chips or
sediment are submerged under water so the expelled oil from the sample will float to
the top of the water (Fig. 5.1). Once expelled, the oil is no longer in contact with the
minerals. However, in the natural environment the organic matter remains in intimate
contact with the mineral assemblage and can undergo a large number of geochemical
processes in association with the mineral surfaces (Alexander et al., 1982; Goldstein,
1983; Johns, 1979). The resulting pyrolysates are similar to mature oils in many ways
but biomarkers are commonly enriched in the less mature isomers. An explanation for
this observation is a stronger acid than water may be needed for the isomerization of
biomarkers, or any saturated chiral carbon in general (Larcher et al., 1986; Sieskind,
1979). This is where the catalytic effects of mineral surfaces are important processes.
Numerous studies have shown that the mineral interactions exert considerable
influence on the quality and quantity of organic matter evolution (Evans and Felbeck,
1983; Horsfield and Douglas, 1980; Huizinga et al., 1987a,b; Larcher et al., 1988; Lu
et al., 1989; Peters et al., 1990; Spiro, 1984; Tannenbaum and Kaplan, 1985;
Tannenbaum et al., 1 986a,b).
The effects of the minerallorganic reactions will influence the rate of bitumen
generation and biomarker conversion, but once removed from the mineral matrix,
these reaction rates can change. The timing of the oil expelling process is unknown
and therefore experimental results using the conventional hydrous pyrolysis technique
may be misleading. But if the pyrolysate is confined with the minerals for the
duration of the heating experiments, a more realistic set of results would be expected.
The method of aqueous confinement pyrolysis was employed to more
realistically simulate the conditions found in the natural system (Fig. 5.2). This was
done by confining the organic compounds to the inorganic matrix during the entire
duration of the experiment. To avoid the potential problem of bitumen partitioning
away form the inorganic sediment matrix, these experiments were done under hydrous
but also in a confined pyrolysis system. The confined pyrolysis system eliminated the
149
large headspace from the reactor and also eliminated the large excess of water, thereby
confining the organic pyrolysates to the bulk inorganic matrix. This principle is
adapted after the confined-system pyrolysis and compaction pyrolysis methods
recently used to study hydrocarbon generation (Monthioux et al., 1985; Blanc and
Connan, 1992; Takeda et al., 1990). High pressure mini-reactors were adapted for this
process. By combining the advances in our understanding of the actual organic
chemical reactions which occur on mineral surfaces (Kissin, 1987; Lao et al., 1989;
Regtop et al., 1985; Smith et al., 1989; Solomon, 1968; Weres et al., 1988; Wilson et
al., 1986) and under high temperature aqueous conditions (Breslow, 1991; Bloun et
al., 1981; Depeyre and Flicoteaux, 1991; Siskin and Katntzky, 1991 and references
therein), a more realistic experimental procedure for hydrothermal simulations was
developed.
150
EXPERIMENTAL
Samples. The samples used in the pyrolysis experiments were the following:
All-i 12-29 PC-5, a surface sediment obtained from the Northern Trough of Guaymas
Basin in 1985; DSDP 481A-8-7 (top of pipe); and DSDP 481A-22-7 (top of pipe).
The locations of the samples in the sediment column are shown in Fig. 5.3. The
downcore samples were selected from sediments above and below a major sill
intrusion that have not been thermally altered by the intrusion.
Hydrous pyrolysis experiments. Pyrolysis experiments were performed in
SnoTrik® T3 16 stainless steel high pressure pipes rated at 60,000 psi, sealed with end
caps and heated in an air circulating oven where the temperature was set at 330° ±2°C.
The reaction vessels and sediment samples were placed in a glove bag and flushed
with five bag volumes of Ar. For each experiment 0.85g of dried sediment was
combined with 0.250 mL of ultrapure water. Each sediment sample was homogenized
and separated into three subsamples. Each sample was pyrolyzed for 24, 48 and 72
hrs.
Extraction and fractionation. The reaction vessels were removed from the
oven and cooled to room temperature upon completion of the heating experiments.
The reaction vessels were extracted with two 1 mL portions of methanol followed by
five I mL portions of methylene chloride. The solvents and water from each pyrolysis
experiment were combined in a centrifuge tube and the organic fraction separated and
collected. The water was extracted with two additional portions of methylene chloride
and the two methylene chloride fractions were combined. The methylene chloride was
dried with anhydrous sodium sulfate and passed through an activated copper column
to remove the elemental sulfur. The solvent was removed using a rotary evaporator at
30°C. The total extract was redissolved in 2 mL of methylene chloride and
deasphalted with 100 mL of heptane. The asphaltenes were allowed to precipitate
overnight and removed by filtration. The deasphalted fractions were concentrated to 2
mL and fractionated by column chromatography (30 cm x 1 cm) packed with 3.8 g
alumina (fully active) over 3.8 g silica gel (fully active). The samples were separated
into three fractions by elution with 50 mL heptane (nonpolar, Fl), 50 mL toluene
(aromatic, F2) and 25 mL methanol (polar, F3).
Gas chromatography. Gas chromatography (GC) of the pyrolysate fractions
was performed with a Hewlett Packard 5890A equipped with a 30 m x 0.25 mm i.d.
DB-5 open tubular column (0.25 jim film thickness). The GC oven was heated using
151
the following program
isothermal for 2 mm. at 65°C, 4°/mm. to 310°C, and
isothermal for 30 mm., with the injector at 290°C, detector at 325°C, and helium as the
camer gas.
Gas chromatography-mass spectrometry. The gas chromatography-mass
spectrometry (GC-MS) was performed on a Finnigan 9610 gas chromatograph
coupled to a Finnigan 4021 quadrupole mass spectrometer operated at 70 eV over the
mass range 50-650 dalton and a cycle time of 2.0 s. The GC oven temperature was
programmed at isothermal for 2 mm. at 65°C, 3°/mm. to 3 10°C, and isothermal for 30
mm., with the injector at 290°C, and helium as the carrier gas. The MS data were
processed with an on-line Finnigan-Incos 2300 computer data system.
152
RESULTS AND DISCUSSION
The gas chromatograms of the aliphatic, aromatic and NSO fractions for all of
the unaltered and pyrolyzed sediment extracts are presented in Appendix 4. With the
exception of the 48 hr pyrolysis of sample 481 A-22-7 (top), which developed a leak
during the experiment, all of the confined system pyrolysis experiments maintained a
pressure tight seal. The molecular ratios of the 48 hr pyrolysis of 481A-22-7 (top)
were calculated and are presented in the results section, although quantitatively there
was a significant drop in the bitumen yield.
All-I 12-29 PC-5. Results for the aliphatic fractions are summarized in Table
5.1. The unheated surface sediment from the Northern Trough of Guaymas Basin was
characteristic of other surface sediments from that region (Simoneit et al., 1979). For
example, the n-alkanes have a Carbon Preference Index (CPI) of 5.8, and the major
triterpenoid was diploptene. All of the heating experiments of this sediment generated
bitumen with -alkane distributions typical of oils from the Guaymas Basin. The CPI
was 1 for all three heating durations; Cmax was 15 to 17; and the Pr/Ph ranged from I
to 1.1. There was a progressive increase in the amount of -alkanes relative to
pristane and phytane as a function of time. Pristane and phytane were the major
compounds in the 24 hr experiment but were secondary in the 72 hr experiment.
The distributions of the triterpenoid hydrocarbons for the unaltered and heating
experiments for the surface sediment are shown in Fig. 5.4. The triterpane distribution
of the 24 hr experiment ranges from C27 to C35 (C28 missing) and consists primarily
of the 17a(H),2l(H)-hopanes and a lesser amount of the l7(H),21a(H)-hopanes
(moretanes). The C-22 S to R epimer ratio of the 17a(H),2113(H)-31-homohopane is
22S/(22S ± 22R) = 0.42,
not equivalent to the maturity of a typical crude oil
(equilibrium ratio = 0.60, Ensminger et al., 1974, 1977), but it is typical for some
hydrothermal oils previously reported (Kawka and Simoneit, 1987). The S/(S + R)
stays relatively constant for the 48 hr and 72 hr experiments, but the longer duration
heating experiments resulted in a large amount of destruction of the biomarkers. Plots
of the relative abundances of some triterpenoid hydrocarbons are shown in Figure 5.5.
The relative amounts of the triterpenoid biomarkers indicate that the triterpenoid
molecular ratios are probably affected more by preferential destruction rather than
interconversion from one epimer to another.
Fragmentograms of the steroid hydrocarbons are presented in Fig. 5.6. The
unaltered sample is dominated by sterenes and all three heating experiments are
153
dominated by C27 to C29 steranes, primarily the 5a(H),14a(H),17a(H)-20R isomers,
with lower amounts of the 5f3(H),14a(H),17a(H)-20R isomers. There was little
change in the sterane distribution as a function of heating time.
The aromatic fraction of the unaltered sample was dominated by perylene,
primarily derived by diagenesis (Louda and Baker, 1984), but the distributions of the
major resolved aromatic compounds were dominated by Diels' hydrocarbon (1,2-(3methylcyclopenteno)phenanthrene, DHC-2), with a lesser amount of a C18 isomer
(DHC-1), in the heating experiments (Fig. 5.7). Diels' hydrocarbon, common in
Guaymas Basin oils, has been used as an indicator of the rapid hydrothermal
petroleum generation processes (Kawka, 1990; Simoneit et al., 1992). The rest of the
aromatic compounds present in these fractions are primarily low molecular weight
PAH and alkyl-PAH (i.e. phenanthrene and methyl-, dimethyl- and
trimethylphenanthrenes).
Several homologous series of ketones, ranging from C14 to> C33, were present
in all of the heating experiments. They were some of the major components in the
NSO fractions, with alkan-2-ones being the highest in concentrations, with lesser
amounts of the 3-, 4- 5- (and higher) homologs. The isoprenoid phenols were also
generated in the heating experiments, although they were minor components.
481 A-8-7 (top pf pipe). The results of the aliphatic fraction are presented in
Table 5.2. All of the heating experiments of this downcore sediment generated
bitumen with -alkane distributions typical of oils from the Guaymas Basin. As with
the surface sediment, there was a progressive increase in the -alkanes relative to the
isoprenoid hydrocarbons pristane and phytane with respect to heating duration. The
aliphatic fraction of the 48 hr experiment was characterized by the appearance of a
large hump or unresolved complex mixture (UCM) in the fl-C25 to -C35 range.
The mass fragmentograms characteristic of the triterpenoid hydrocarbons for
the unaltered and heating experiments are shown in Fig. 5.8. The triterpane
distribution of the 24 hr experiment was similar to that of the surface sediment
pyrolysis where the hopanes ranged from C27 to C35 (C28 missing) and consisted
primarily of the 17a(H),21 (H)-hopanes and a lesser amount of the l7(H),2la(H)hopanes (moretanes). The C-22 S to R epimer ratio of the 17a(H),21(H)-3lhomohopane is 22S/(22S + 22R) = 0.46, not equivalent to the maturity of a typical
crude oils, but the S/(S + R) = 0.59 in the 48 hr experiment, indicating that the epimers
are in their equilibrium ratios. The 48 hr experiment resulted in a large increase in the
amount of biomarkers relative to the 24 hr experiment (Fig. 5.9), corresponding to the
154
formation of the large UCM in the aliphatic fraction. There was significant
destruction of the biomarkers in the 72 hr experiment. The reversal in the C31
homohopane S/(S + R) ratio in the 72 hr experiment is the result of hopane
destruction.
Fragmentograms of the steroid hydrocarbons are presented in Fig. 5.10. The
unaltered sample is dominated by C27 to C29 sterenes. The 24 hr experiment consists
of C27 to C29 steranes, primarily the 5a(H),l4cL(H),17a(H)-20R isomers, with lower
amounts of the 513(H),14a(H),17a(H)-20R isomers. Extensive isomerization of the
steranes occurred in the 48 hr experiment resulting in a pattern representative of a
fully mature oil. Destruction of the steranes occurred in the 72 hr experiment, a loss
of sterane hydrocarbons analogous to the destruction of the triterpanes. The remaining
steranes were primarily the 5a(H),14a(H),l7a(H)-20R isomers, with lower amounts of
the 5(H),1 4(H), 1 7a(H)-20R isomers.
A summary of the PAH quantitation is shown in Fig. 5.11. The aromatic
fraction of the unaltered sample was dominated by perylene, and there was a trend of
perylene destruction accompanied by pyrolytic PAH formation as a function of time in
the heating experiments. Diels' hydrocarbon was also formed in relatively high
amounts, but in lower amounts compared to the concentrations obtained by the
pyrolyses of the surface sediment PC-S. The pyrolyses of this sediment formed Diels'
hydrocarbon in concentrations approximately 30% of the surface sediment pyrolyses.
The multiple homologous series of ketones were all present in the heating
experiments and were well resolved and in high amounts in the NSO fractions. As
with the pyrolysis of the surface sediment, the alkan-2-ones were in highest
concentrations, with lesser amounts of the 3-, 4- 5- (and higher) homologs. The
isoprenoid phenols were also generated in the heating experiments, although they were
minor components.
481A-22-7 (top of pipe). The results of the aliphatic fraction are presented in
Table 5.3. All of the heating experiments of this sediment generated bitumen with
alkane distributions typical of those found in oils of Guaymas Basin. The relative
amounts of -alkanes to pristane and phytane were much higher in these experiments
than in the previous experiments. The 48 hr experiment developed a leak some time
during the experiment, which resulted in an overall decrease in extactable organic
matter.
The mass fragmentograms characteristic of the triterpenoid hydrocarbons for
the unaltered and heating experiments are shown in Fig. 5.12. The triterpane
155
distribution of the unaltered sediment consisted of hop-17(21)-ene and the C29 to C31
1313-hopanes. The pyrolysis experiments formed hopanes ranging from C27 to C35 (C28
missing) in their fully mature configurations, the C-22 S to R epimer ratio of the
17a(H),2l(H)-3l-homohopane is 22S1(22S + 22R) = 0.59 in the 48 hr experiment
and 0.58 in the 72 hr experiment. Fig. 5.13 shows the relative amounts of the selected
hopane biomarkers. The minimum values of the 48 hr experiment correspond to the
pressure vessel that leaked during the experiment.
The sterane plots are shown in Fig. 5.14. Conversion from the sterene pattern
of the unaltered to the oil-like pattern occurred in only 24 hr, indicating that the
extensive isomerization to the fully mature signature is rapid. This pattern remained
unchanged for the 48 and 72 hr experiments.
The histograms from the PAH quantitation are shown in Fig. 5.15. The
aromatic fraction of the unaltered sample was dominated by perylene, and there was a
large amount of perylene destruction accompanied by pyrolytic PAH formation as a
function of time in the heating experiments. Diels' hydrocarbon was formed in only
trace levels in the 24 and 72 hr experiments.
The homologous series of ketones were the major compounds of the NSO
fractions of the 24 and 72 hr experiments, with only trace amounts in the 48 hr
experiment. The low amount of ketones in the 48 hr experiment is likely an artifact
due to the leak in the reaction vessel. The isoprenoid phenols were not formed in any
of the heating experiments of sediment 481 A-22-7 (top).
The results clearly show that there are significant catagenetic changes as a
result of the heating experiments, demonstrating that under these experimental
conditions pyrolysates very similar to hydrothermal oils can be generated by
confinement pyrolysis.
Effects of time on the pyrolysates. Increasing the duration of the experiments
from 24 to 72 hr resulted in the general trend of increasing the amount of -a1kanes
relative to the isoprenoids pristane and phytane. Isoprenoids can be derived from
several sources such as the phytyl side chain of chlorophyll (Cox et al., 1970; Maxwell
et al., 1972), from tocopherols (Goosens et al., 1984), as well as from ether lipids from
Archaebacteria (Michaelis and Albright, 1979). It is possible that these isoprenoids
are released from the kerogen earlier than the -alkanes due to slightly weaker
chemical bonds linking the isoprenoids to the bound matrix.
The triterpenoid biomarker distribution in the pyrolysis of the surface sediment
All- 112-29 PC-5 is probably the result of the simultaneous generation, isomerization
156
and destruction of the compounds in this series. The distribution after 24 hr closely
resembles that of an oil, although the C31-homohopane SI(S + R) ratio did not indicate
full maturation. The 48 and 72 hr experiments appear to be post-mature, due to the
destruction of the biomarkers.
A similar trend was observed in the 481A-8-7 (top) sediment, but this sample
reached full maturation after 48 hr, both in the hopane and sterane biomarkers. The
reversal in the C31 -homohopane SI(S + R) ratio after 72 hr was a result of a
preferential loss of the R isomer from the extensive loss of the biomarkers due to
thermal destruction.
Sample 481 A-22-7 (top) also reached full maturation in both the steranes and
hopanes after 48 hr and maintained these biomarker distributions through to the 72 hr
experiment. Considering that the 48 hr experiment leaked, a comparison of the 24 hr
to the 72 hr experiment suggests little change, or even a slight increase in the amount
of hopanes for the 72 hr duration.
Using the hopane and sterane biomarkers as a measure, the "oil window" was
reached within 72 hr of heating for all three sediments. This demonstrates that
maturation of the sedimentary organic matter accompanied by full hopane and sterane
isomerization can be achieved from recent, thermally-unaltered sedimentary organic
matter. These biomarker conversions match closely those changes observed in
sediments from DSDP Site 481A, where the sedimentary organic matter in the
proximity of a dolerite sill was thermally altered and resulted in maturation of the
biomarker signatures (see Ch. 2, Figs. 2.17 and 2.18).
The PAH distributions reflect the destruction of perylene coupled with the
generation of lower molecular weight aromatic compounds. This trend was also seen
in the sediments that were naturally altered in DSDP Site 481A (see Ch 2. Fig. 2.19).
The experimental set that most closely matched the natural trend was the 481 A-22-7
(top) sediment. But in the experiments a large amount of anthracene was also formed,
a PAR which is commonly found in hydrothermal oils (Kawka and Simoneit, 1990).
Anthracene was in very low concentrations or not detected in the naturally altered
sediments of Site 481 A.
Effects of depth on the pyrolysates. The most striking trend observed as a
function of sediment depth was in the polycyclic aromatic hydrocarbons. Both the
surface sediment and sample 481 A-8-7 (top), a sample from the hydrothermally
unaltered sediments above the sill, generated a large amount of Diels' hydrocarbon,
but this compound was present in only trace amounts in the pyrolysates of 481 A-22-7
157
(top). This compound has been proposed as a tracer of high temperature alteration of
sedimentary organic matter, but its absence suggests that the formation of Diels'
hydrocarbon is more than just temperature dependent, that its formation is a function
of the nature of the organic matter. A plot showing the relative amounts of Diels'
hydrocarbon as a function of temperature for the three samples is shown in Fig. 5.16.
Diels' hydrocarbon is thought to be primarily derived from functionalized steroid
compounds in the sediments, and under hydrothermal conditions the steroid is rapidly
dehydrogenated to the triaromatic steroid hydrocarbon. The results indicate that the
extent of diagenesis affects the yield of Diels' hydrocarbon. It is possible that as
diagenesis progresses, the functionalized steroid natural products slowly become
defunctionalized and reduced to saturated sterane hydrocarbons. Hydrothermal
alteration of saturated steranes favors epimerization and destruction reactions rather
than aromatization reactions. This would explain the lack of Diels' hydrocarbon in the
pyrolysis of the deepest sediments. The present seabed oils, which contain high
amounts of Diels' hydrocarbon (Kawka, 1990), are likely derived from sedimentary
organic matter that has not undergone extensive diagenesis, in agreement with the
young 14C ages of the oils (Peteret aL, 1991).
The series of ketones present in all of the pyrolysates have also been found in
hydrothermal oils, extracts of hydrothermally-altered sediments, and simulated
pyrolysis experiments. The ubiquitous presence of these compounds in the bitumen
and oils of high temperature origin (Leif et al., 1992; George and Jardine, 1993)
suggests that these compounds may be good indicators of high temperature
hydrothermal alterations of organic matter. The isoprenoid phenols, previously
identified as common constituents in the NSO fractions of hydrothermal oils, were
generated in all of the heating experiments. Their concentrations were low, but the
distributions of these compounds in the heating experiments matched those in the
seabed oils.
The procedure of confinement pyrolysis was successful in converting the
recent, immature sedimentary organic matter to products resembling mature oils or
sedimentary organic matter that has been extensively altered by high temperature
hydrothermal activity. Parallel experiments using the conventional hydrous pyrolysis
technique were not performed. Therefore, it cannot be concluded that these
conversions would have occurred at different rates under hydrous pyrolysis
conditions. Although, numerous experiments have been carried out on Guaymas
158
Basin sediments using conventional hydrous pyrolysis conditions under similar time
and temperature conditions, full biomarker isomerization was never observed.
CONCLUSIONS
The procedure of confinement pyrolysis has been performed using whole,
unconsolidated sediments from the Guaymas Basin hydrothermal system. Thermal
alteration of immature sedimentary organic matter to a fully mature extractable
bitumen has been achieved using three different sediments from the Guaymas Basin
hydrothermal system, with full maturation occurring after 48 hr. Comparison of the
major compounds in the aliphatic, aromatic and NSO fractions generated in the
heating experiments with those in naturally-altered sediment sequences indicates a
reasonable match in the quality and quantity of those components.
Application of these experimental results to oil generation in the Guaymas
Basin indicates that diagenesis may play an important role in altering the nature of the
source organic matter, especially the steroids and their derivatives. The aliphatic
ketones appear to be good universal indicators for high temperature catagenetic
processes.
159
Table 5.1. Selected parameters for the aliphatic fractions of All- 112-29 Pc-S.
All-il 2-29 PC5
48 hr @ 330°c 72 hr @ 330°C
Parameter
Unaltered
24 hr @ 330°C
-a1kane
15-35
12-39
12-39
11-39
CPI
5.8
1.0
1.0
1.0
Cm
31
17
15
15
Pr/Ph
n.d.
1
1.06
1.12
Pr/n-C17
n.d.
1.16
0.98
0.81
PhI-C1g
n.d.
1.33
1.04
0.87
S/(SR)
-
0.42
0.37
0.45
0.46
0.38
0.44
range
C31
S/(SR)
C32
29,30,31H
29,30,31M
-
2.48
1.75
2.03
27R129R
-
1.96
2.40
3.60
27R128R
2.48
2.48
4.50
28R129R
0.79
0.97
0.80
n.d. = not determined
S/(SR)
C-22 S and R epimer ratios for C31 and C32 ct-homohopanes
29,30,31 H
29,30,31 M
27R
29R
C29 + C30 +
C31 a-hopanes
C29 + C30 + C31 moretanes
C27 20 R acrct-sterane
C29 20 R ctact-sterane
27R
28R
C27 20 R acta-sterane
28R
29R
C28 20 R ctact-sterane
c28 20
R ctaa-sterane
C29 20 R acta-sterane
160
Table 5.2. Selected parameters for the aliphatic fractions of 481A-8-7 (top of pipe).
481 A-8-7 (top of pipe)
48 hr @ 330°C 72 hr @ 330°C
Parameter
Unaltered
24 hr @ 330°C
n-alkane
range
12-32
10-39
10-38
12-38
CPI
3.6
1.0
1.0
1.0
Cm
29
15
15
15
Pr/Ph
0.47
2.3
2.0
2.2
Pr/n-C17
0.31
1.10
0.85
0.80
Ph/n-C18
1.04
0.56
0.50
0.40
0.46
0.59
0.46
0.49
0.55
0.48
2.04
3.30
1.64
S/(S+R)
C31
S/(S+R)
-
C32
29.30,31H
29,30,31 M
27R129R
-
1.44
1.05
3.79
27R128R
-
2.4
1.86
4.34
0.60
0.56
0.87
28R129R
SI(S+R) = C-22 S and R epimer ratios for C31 and C32 a-homohopanes
29,30.31 H
29,30,31 M
27R
29R
C29 + C30 + C3
C29 + C30
+ C moretanes
20 R aaa-sterane
C29 20 R aaa-sterane
C27
a-hopanes
27R
28R
C
20 R ctaci-sterane
C28
20 R acLa-sterane
28R
29R
C28
20 R acta-sterane
C29
20 R aaa-sterane
161
Table 5.3. Selected parameters for the aliphatic fractions of 481 A-22-7 (top of pipe).
481 A-22-7 (top of pipe)
48 hr @ 330°C 72 hr @ 330°C
Unaltered
24 hr @ 330°C
n-alkane
range
13-31
10-37
13-38
CPI
4.13
1.1
1.0
1.1
Cm
29
19
16
17
Pr/Ph
0.44
2.3
Pr/n-C17
1.17
0.44
Ph/n-C18
4.43
0.20
Parameter
S/(SR)
12-38
2.4
-
0.29
0.13
0.47
0.59
0.58
-
0.57
0.56
0.48
-
2.40
3.81
3.56
27R129R
-
0.68
0.50
0.57
27RJ28R
-
2.63
1.71
1.37
28R129R
-
0.26
0.29
0.41
C31
S/(S+R)
C32
29,30.31H
29,30,31 M
S/(S+R) = C-22 S and R epimer ratios for C31 and C32 a-homohopanes
29,30.31 H
C29 + C30 + C31 cL-hopanes
29,30,3 1 M
C29 + C30 + C31 moretanes
27R
29R
C27 20 R aaa-sterane
C29 20 R aaa-sterane
27R
28R
C27 20 R cLacL-sterane
28R
29R
C28 20 R aaa-sterane
C28 20 R aaa-sterane
C29 20 R ctcta-sterane
162
0
Expelled
Water
Reaction Vessel
Sample
Before Heating
After Heating
Figure 5.1. Diagram showing expulsion of pyrolysates during conventional hydrous
pyrolysis.
163
r
Ijr.J(Ii
I III
_____________Sample/Water
Fri i
Before Heating
____
During Heating
i
fl
Reaction Vessel
i
After Heating
Figure 5.2. Diagram showing the principle of confinement pyrolysis.
164
HOLE 481
AThI,22'
0
HOLE 481A
Water depth - 1998 m
*
UNIT I
Olive brown
muddy diatom
ooze and
;
turbidites
--ci
4
_--_
6
Megaturbidite
1
Megaturbidite
100
LI8(4-8- 7
('-np)
4
4
Sandstone
.
- i.
O
E
,-.
Chert and
dolerite sills
complex
17
o
_-....-_-
.
0)
L45(A22
20::
:
-
UNIT II
21
p--
- -.--
23
Laminated
diatom mud
Mudflow II
j
26
0.26 27 I
29
!
!
-.
Mudilow Ill
Dolerite
4
32
33
-
Dolerite
Figure 5.3. Lithologic column for DSDP Site 481A, location of samples for pyrolysis
are shown (Curray et al., 1982).
165
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97.1
191
-
-I-- 1- -
. -i..
I
I
------- I---
3o.c5
) 100.
255
. (Z
3O°
191
;'°'P
Z"3
5
2lpx
3,o((
qeq
l
()(
ii
r1
I-
t
cJlOO.
1j iO(3"
2'o?1
II
3t(3
191
I
II
I
II
I
II
LL-I
)LJD iL
-
'-i
3Z°
3o
4 ieo.i
191
23
J
'°
it JI
2000
66:48
2100
78:00
2288
73:20
2300
76:40
2480
80:00
2508
83:20
2608
86:40
Figure 5.4. Representative mass fragmentograms mlz 191 for the triterpenoid
hydrocarbons in the extracts of sediment All- 112-29 PC 1: a) Unaltered; b) 24 hr @
330°C; c) 48 hr @ 330°C; d) 72 hr @ 330°C.
a.)
100
90
80
70
29H
60
-0-- 29M
50
40
30
20
20
30
40
50
60
70
80
Time (hrs)
100
90
80
70
30H
60
-0-- 30M
50
40
30
20
20
30
40
50
60
70
80
Time (hrs)
Figure 5.5. Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment All-i 12-29 PC-5: a) 17a(H),2l(H)-29-hopane and
17f3(H),21a(H)-29-hopane vs. time, and b) 17a(H),21(H)-3O-hopane and
1 713(H),2 I a(H)-30-hopane vs. time.
167
c)
100
90
80
70
3laS
60
a-- 3laR
50
40
30
20
20
30
40
50
60
70
80
Time (hrs)
d)
100
90
80
70
32aS
60
a-- 32aR
50
40
30
20
20
30
40
50
60
70
80
Time (hrs)
Figure
5.5.
Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment All- 112-29
PC-5:
c) 1 7a(H) ,2 1 (H)-3 1 -hopane (22S) and
17(H),21a(H)-31-hopane(22R) vs. time, and d) 17a(H),21(H)-32-hopane (22S) and
I 7(H),2 1 a(H)-32-hopane(22R) vs. time.
168
27 3Z
"i) 1ØØ
TOT
28
Ai
OCK
) iøe.
27
28
0iZ
2°i
I
I
oz
27
28
Pitt
4 iee.
27
TOT
-
A
-
PA ..
I"
I
1888
60:80
1980
63:20
2008
66:40
2108
78:08
2280
73:20
I
2308
76:40
Figure 5.6. Representative mass fragmentograms (mlz 215, 217, 218, 257, 259) for
the steroid hydrocarbons in the extracts of sediment All-li 2-29 PCi: a) Unaltered; b)
24 hr @ 330°C; c) 48 hr @ 330°c; d) 72 hr @ 330°C.
fQ
CD
'1
o
()
-t
00
C)
l)
CD
CD
(Jo
C)
O_ 0
CD
-tO
k)
CD
Diets HC.2
Diels I-IC-I
Coronene
Benzo(g,h,i)perylene
Dbenzo(a,h)anthracene
Perylene
flenz(a)pyrenc
Benz(e)pyrene
Chtysene/Triphenyene
Benz(a)anthracene
2,3-Renzofluorene
Pyrene
Fhioranthene
Anthracene
Phenanthrene
Dibenzothiophene
-
'0
-a-
(J
Cone. (ng/g sed.)
5.3
9.
Conc. (nglg sed.)
Cone. (ng/g seth)
tJ
o
-
o
Cone. (nglg sad.)
C)
C,-.
0
5.3
170
If-
3C5
191
3'
30oC(5
) lee.
2'7°'
191
12
?Z'
33°<(3
;L1((3
AJiJLJ
ç_(3
ç
£
((:3
;::
c)180.
2'1'
A
131
32
II
T tlLi
A
IZ
oo3
Z9()
d) 108.8.
5.
191.
z
Li
LJL
2000
56:40
2188
70:80
2288
73:28
2388
76:48
2408
80:00
2500
83:20
2688
86:40
Figure 5.8. Representative mass fragmentograms mlz 191 for the triterpenoid
hydrocarbons in the extracts of sediment 481 A-8-7 (top): a) Unaltered; b) 24 hr @
330°C; c) 48 hr @ 330°C; d) 72 hr @ 330°C.
171
c)
100
90
U
80
70
60
29H
50
-0-- 29M
40
30
-
20
10
0
20
30
40
50
60
70
80
Time (hrs)
100
90
U
80
70
60
30H
50
-0----
40
30M
30
20
10
0
20
30
40
50
60
70
80
Time (hrs)
Figure 5.9. Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment 481A-8-7 (top): a) 17a(H),2l3(H)-29-hopane and
17(H),21a(H)-29-hopane vs. time, and b) 17a(H),2l(H)-3O-hopane and
I 73(H),2 I a(H)-30--hopane vs. time.
172
c)
100
90
Q
70
.
60
3laS
50
?
-D--- 3laR
40
30
20
10
0
20
30
40
50
60
70
80
Time (hrs)
d)
100
90
Q
70
.
60
?
50
32aS
40
-D--- 32aR
10
0
20
30
40
50
60
70
80
Time (hrs)
Figure 5.9. Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment 481A-8-7 (top): c) 17a(H),2113(H)-31-hopane (22S) and
I 713(H),2 I a(H)-3 1 -hopane(22R) vs. time, and d) 1 7a(H),2 1 3(H)-32-hopane (22S) and
1 7(H),2 I a(H)-32-hopane(22R) vs. time.
173
27
29
L
2
I
TOTAL
2
,) l00.0-j
27
I
291
25°
270 2g17
ii
I
J[
(3k'
IL
ricA Z°
/9°s
210
c)lOO.8
:1) tq 4ei,'
(31Z
2
28ç3
29-
2l?)?\
25
II
¶
TOTAL
zf)
J)
z9J
"
IL
I
4 100.
27
I'
.1
1800
60:08
1380
63:20
2000
66:40
2100
70:00
2200
73:20
2300
76:40
Figure 5.10. Representative mass fragmentograms (mlz 215, 217, 218, 257, 259) for
the steroid hydrocarbons in the extracts of sediment 481 A-8-7 (top): a) Unaltered; b)
24 hr @ 330°C; c) 48 hr @ 330°C; d) 72 hr @ 330°C.
174
1500
481A-8-7 (top)
1250
°
1000
.E
750
0
Unaltered
500
250
A
I000
800
481A.8-7 (top)
24 hr @ 330 C
600
400
0
0
c)
IL
1000
481A-8-7 (top)
48 hr (
330 C
8001
600]
400
0
0
200
d)
I,
1000
800
600
400
0
0
200
0
p
.0
V
V
V
0
V
V
0
0
2
U
Figure 5.11. Histograms of the major aromatic compounds present in the extracts of
sediment 481A-8-7 (top): a) Unaltered; b) 24 hr @ 330°C; c) 48 hr @ 330°C; d) 72 hr
@ 330°C.
175
i) 103.
191
2d1
3
rr
1A
-
_h)
,) ioe.
2e3
3Jof(
191
213o(
3L
1
liZ
III
c) 180.
2°T'3
191
32o3
5
3o((3
q((3
4JJ
2o'
I
I.
LJLALJLLU
I.
1
) 100.
191
2cI(3
34
tZ
'
2800
66:48
2108
70:80
I
I
2208
73:28
2300
76:48
I
2480
80:80
I
2508
83:20
I
2680
86:40
Figure 5.12. Representative mass fragmentograms mlz 191 for the triterpenoid
hydrocarbons in the extracts of sediment 481 A-22-7 (top): a) Unaltered; b) 24 hr @
330°C; c) 48 hr @ 330°C; d) 72 hr @ 330°C.
176
.)
100
90
80
70
60
29H
50
.
?
40
..d
30
?
-0-- 29M
2
10
0
20
30
40
50
60
70
80
Time (hrs)
100
90
U
.
70
60
30H
50
-0-- 3CM
40
20
10
0
20
30
40
50
60
70
80
Time (hrs)
Figure 5.13. Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment 481A-22-7 (top): a) 17a(H),21(H)-29-hopane and
17(H),21a(H)-29-hopane vs. time, and b) 17a(H),21(H)-3O-hopane and
I 7(H),2 1 a(H)-30-hopane vs. time.
177
100
90
80
70
60
3laS
50
-0----
40
3laR
30
20
10
0
20
30
40
50
60
70
80
Time (hrs)
d)
Q
100
90
70
32aS
60
-0----
32aR
50
40
30
20
20
30
40
50
60
70
80
Time (hrs)
Figure 5.13. Relative abundance of selected triterpane biomarkers in the heating
experiments of sediment 481 A-22-7 (top): c) I 7ct(H),2 I (H)-3 I -hopane (22S) and
17(H),21a(H)-31-hopane(22R) vs. time, and d) 17x(H),21f3(H)-32-hopane (22S) and
I 7(H),2 1 a(H)-32-hopane(22R) vs. time.
178
4)10U.8
z7
TOT
25
27
J cAJ\J
Q180.
1L
/
I
211)
I
2112
.4-
27
z8
1
2Ifl
,III
Ii
I
/i
d
i
2S
c) 180.
2
29
flpf2
)ioo.
29
S
2°'o'Z
1880
68:00
1980
63:20
2880
66:40
2180
70:80
2200
73:20
2300
76:48
Figure 5.14. Representative mass fragmentograms (mlz 215, 217, 218, 257, 259) for
the steroid hydrocarbons in the extracts of sediment 481 A-22-7 (top): a) Unaltered; b)
24 hr @ 330°C; c) 48 hr @ 330°C; d) 72 hr @ 330°C.
179
2500
481A-22-7 (top)
-C
Unaltered
2000
1500
l000
0
C.)
500
n
400
7)
481A-22-7 (top)
24 hr @ 330 C
300
200
(1
C
0
100
0
175
C)
481A.22.7 (top)
4S hr @ 330 C
150
0
125
C
100
75
C
50
25
0
300
491A.22-7 (top)
72 hr @ 330 C
C?
200
C
100
C.)
0
C?
C
.
I
E
C?
C?
00
=
U
Figure 5.15. Histograms of the major aromatic compounds present in the extracts of
sediment 481A-22-7 (top): a) Unaltered; b) 24 hr @ 330°C; c) 48 hr @ 330°C; d) 72
hr @ 330°C.
3000
-0---
All-i 12-29 PC-5
2000
a--- 481A-8-7 (top)
U
0
1000
481A-22-7 (top)
0-I-
20
30
40
50
60
70
80
Heating Duration (hr)
Figure 5.16. Plot showing the yields of Diels' hydrocarbon (DHC-2) in the heating
experiments for the three sediment samples.
181
CHAPTER 6
A Proposed Chemical Pathway for the Origin of Ketones in Oils and Sediment
Extracts from the Guaymas Basin Hydrothermal System
182
ABSTRACT
Hydrothermal oils and extracts of hydrothermally altered sediments contain
ketones that appear to be uniquely associated with a high temperature hydrothermal
mode of formation. Oils associated with hydrothermal vents contain several
homologous series of alkanones, ranging in carbon number from C11 to C30 with a
Cmax from C15 to C23. The large variation in Cmax is probably a function of the vent
fluid temperatures which range from 2500 to 350°C. These oils contain alkan-2-ones
in highest concentrations with slightly lower amounts of 3-, 4-, 5-, (and higher)
alkanones. These compounds are enriched in the interiors of the hydrothermal vent
spires or in downcore hydrothermally-altered sediments, indicating an origin at depth
or in the hydrothermal fluids and not from external biogenic deposition.
Simulation of the natural hydrothermal pyrolysis process by laboratory
hydrous pyrolysis techniques provides information regarding the mode of alkanone
formation. Hydrous pyrolysis of -C32H66 at 330 and 350°C for 72 hr with water only
or water with inorganic additives has been studied using a stainless steel reaction
vessel. In each experiment a similar distribution of alkanones was formed from the
cracking of the -a1kane. The product distributions indicate a reaction pathway
consisting of -alkanes and a-olefins as primary cracking products with internal
olefins, alkanones and alkanals as secondary reaction products of the a-olefins. The
product compositions were modified by ionic strength, pH and reactive species such
as sulfate, elemental sulfur and sulfide.
Hydrous pyrolyses of Messel shale spiked with molecular probes have been
performed under similar time and temperature constraints to produce alkanone
distributions like those found in the hydrothermal vent oils.
183
INTRODUCTION
Numerous reports have identified aliphatic ketones in the extractable portion of
sedimentary organic matter. This homologous series of alkan-2-ones occurs with an
odd carbon number predominance and its source is most likely being microbial
(Cranwell, 1977; Simoneit, 1978, 1979; Brassell et al., 1980; Albaigés et al., 1984).
Alkanones with an oddleven predominance produced from the incomplete combustion
of n-alkanes or n-alkanols have been identified in aerosols (Simoneit et al., 1991).
Aliphatic ketones with no carbon number predominance have only recently been
reported (Leif et al., 1992; George and Jardine, 1993), with both occurrences being
associated with dolorite sill intrusions into sedimentary sections. Oil shale pyrolyses
generate alkan-2-ones and lesser amounts of 3-, 4-, 5- and 6-ketones (Regtop et al.,
1982, 1985; Rovere et al., 1983). Other products generated in the oil shale pyrolyses
include -alkanes and terminal and internal -alkenes. The origin of the aliphatic
ketones must be related to the high temperature conditions encountered in all the
previous studies. The mechanism by which they are formed is still not understood.
George and Jardine (1993) suggest that the ketones originate by the thermal fission of
alkyl chains linked by ether groups at a variety of chain positions, from 3 to at least 7.
Experiments have been performed which were designed to understand the
chemistry of high temperature hydrothermal systems. Using the procedure of hydrous
pyrolysis, aliphatic ketones have been found to be common pyrolysis products, no
matter what the beginning source material is. This paper presents some results of the
heating experiments and proposes a chemical pathway by which these compounds are
formed.
EXPERIMENTAL
Sample. The seabed oil for this study was sampled from the interior of a
hydrothermal vent collected during Deep Submergence Vessel (D.S.V.) Alvin dives of
March, 1988 (sample 1972-CH1 Interior).
Hydrous pyrolysis experiments. Pyrolysis experiments were performed in
SnoTrik® T316 stainless steel high pressure pipes rated at 60,000 psig (4080 bar),
sealed with end caps and heated in an air circulating oven set at 330° ±2°C. Burdick
and Jackson ultrapure water was used in all experiments. Aliphatic compounds used
in pyrolysis experiments were 1,1 3-tetradecadiene (purity > 97%), 1 -hexadecene
(purity> 97%), eicosane (purity 99%), and dotriacontane (n-C32H66, purity > 97%).
The Messel shale used in the experiments was powdered and Soxhiet extracted with
methanol/methylene chloride for 72 hr prior to the pyrolysis studies. The reaction
vessels with reactant mixtures were placed in a glove bag and flushed with five
volumes of argon. Deoxygenated H20 or D20, prepared by bubbling with argon gas
for 45 minutes, was added and the vessels sealed.
Durations of the heating
experiments ranged from 1 hr to 72 hr.
Extraction and fractionation. The frozen hydrothermal vent sample was
brought to room temperature and an oil sample was removed from the interior of the
vent matrix. The oil was diluted in chloroform and filtered to remove any debris and
passed through an activated copper column to remove the elemental sulfur. The
sample was reduced to 2 mL by rotary evaporation.
The reaction vessels were removed from the oven and cooled to room
temperature upon completion of the heating cycles. The reaction vessels were
extracted with two 1 mL portions of methanol followed by five 1 mL portions of
methylene chloride. The solvents and water from each pyrolysis experiment were
combined in a centrifuge tube and the organic fraction separated and collected. The
water was extracted with two additional portions of methylene chloride and the two
extract fractions were combined. The methylene chloride extract was dried with
anhydrous sodium sulfate and passed through an activated copper column to remove
the elemental sulfur.
The whole oils and pyrolysis extracts were deasphalted with 100 mL heptane.
The asphaltenes were allowed to precipitate for 24 hrs and removed by filtration. The
deasphalted fractions were fractionated by column chromatography (30 cm x 1 cm)
packed with 3.8 g alumina (fully active) over 3.8 g silica gel (fully active). The
185
samples were separated into three fractions by elution with 50 mL heptane (aliphatic,
Fl), 50 mL toluene (aromatic, F2) and 25 mL methanol (polar NSO, F3).
Further fractionation was performed by thin layer chromatography (mc). The
polar NSO fraction was loaded on a silica gel plate (fully active , 20 x 20 cm, 250
.tm), and eluted with a solution of heptane:diethyl ether (20:1). The band
corresponding to Rf 0.25 to 0.50 was the ketone band. The ketones were eluted with
methylene chloride and concentrated by rotary evaporation. Quantitation was by the
addition of n-C24D50 and n-C32D66.
Gas chromatography. Gas chromatography (GC) of the oil fractions was
performed with a Hewlett Packard 5890A equipped with a 30 m x 0.25 mm i.d. DB-5
open tubular column (0.25 pm film thickness). The GC oven was heated using the
following program: isothermal for 2 mm. at 65°C, 4°/mm. to 310°C, and isothermal
for 30 mm., with the injector at 290°C, detector at 325°C, and helium as the carrier
gas.
Gas chromatography-mass spectrometry. The gas chromatography-mass
spectrometry (GC-MS) was performed on a Finnigan 9610 gas chromatograph
coupled to a Finnigan 4021 quadrupole mass spectrometer operated at 70 eV over the
mass range 50-650 dalton and a cycle time of 2.0 s. The GC oven temperature was
programmed at isothermal for 2 mm. at 65°C, 3°/mm. to 3 10°C, and isothermal for 30
mm., with the injector at 290°C, and helium as the carrier gas. The MS data were
processed with an on-line Finnigan-Incos 2300 computer data system.
RESULTS and DISCUSSION
We have been interested in identifying compounds that could be used as
markers to distinguish hydrotherrnally derived oils from conventional reservoir oils.
Progress has been made in understanding the hydrothermal generation process and
formation of certain oxygenated compounds.
Chromatographic behavior of aliphatic ketones. The gas chromatographic
behavior of several ketone isomers is shown in Fig. 6.1. Tetradecan-2-one and
tetradecan-3-one are completely resolved by gas chromatography on a DB-5 column,
but tetradecan-4-one is on a shoulder of a peak formed by the coelution of the 5-,6and 7-tetradecanones. The mass spectra of the pure ketone standards are shown in
Fig. 6.2 and mass spectra of the four peaks in the ketone mixture are shown in Fig.
6.3.
Ketones in hydrothermal oils. Aliphatic ketones are ubiquitous in
unbiodegraded oils associated with high temperature hydrothermal vents in the
Guaymas Basin. Fig. 6.4a shows a gas chromatogram of the polar NSO fraction of a
representative hydrothermally-generated oil. Fig. 6.4b is the ketone fraction isolated
by thin layer chromatography. There was some loss of the alkan-2-one series in
another fraction. These ketones in hydrothermal oils possess a smooth distribution,
analogous to the ii-alkane distributions in mature oils. The aliphatic ketones are
enriched in the interiors of the high temperature vents, suggesting a pyrolytic source.
The alkan-2-ones are usually in highest concentrations, with lesser amounts of 3-, 4-,
5- (and higher) ketones. The same series of ketones has been identified in the
hydrothermally-altered sediments in the proximity of a dolorite sill. The association
of the ketones with sill intrusions, with the exception of the contribution of George
and Jardine (1993), has not been described before in geological samples.
Ketones from the hydrous pyrolysis of n-Cll. The aqueous high
temperature organic chemistry of fl-C32H66 was investigated by pyrolyzing the
hydrocarbon with water only or water with several selected inorganic components
(Leif et al., 1992). The products consisted of a broad distribution of cracking products
with a large amount of unreacted starting material. The cracking products were
alkanes, n-alkenes, and a polar fraction containing -ketones as the major components.
It appears that the primary products are the -alkanes and terminal n-alkenes,
generated by radical cracking, and secondary reactions produce internal -a1kenes and
oxygenated compounds. It is possible that the alkenes are intermediates to the
187
formation of the ketones. Fig. 6.5 shows gas chromatograms of one pyrolysis
experiment conducted in the presence of iron sulfides. Fig. 6.5a is the nonpolar
aliphatic fraction, containing n-alkanes, and Fig. 6.5b is the polar fraction, consisting
of ketones. The alkan-2-ones are highest, with lesser amounts of 3-, 4- (and higher)
ketones. Even under strong reducing conditions the ketones were formed by the
hydrous pyrolysis conditions.
Ketones from the pyrolysis of aliphatic molecular probes with Messel shale. A
series of hydrous pyrolysis experiments was performed by spiking 1,13tetradecadiene, 1 -hexadecene and eicosane on Messel shale and heating at 330°C. The
products were analyzed after 1, 5, 10, 36 and 72 hr. Fig. 6.6 shows the gas
chromatograms of the polar fractions. It was shown that at the termination of the
heating experiments (72 hr), the major compounds were ketones. The distribution of
the ketone isomers is shown in Fig. 6.7. Fig. 6.7a shows the ketones from the reaction
of 1,1 3-tetradecadiene and Fig. 6.7b shows the products from 1 -hexadecene. Both of
these product distributions are dominated by the alkan-2-one, with lesser amounts of
the other ketones. Fig. 6.7c shows the ketones generated from eicosane. The
distribution closely matches the ketone distribution found in the hydrothermal oils
(Fig. 6.8). These experiments indicate that under high temperature hydrothermal
conditions, ketones can be formed from alkenes and alkanes.
Proposed origin of ketones under natural and simulated hydrothermal
conditions. Aliphatic ketones have been shown to be synthesized under natural and
simulated hydrothermal conditions, especially under reducing conditions. A chemical
pathway is proposed where the ketones derive from a short-lived aliphatic alcohol.
Fig. 6.9 shows the general reaction scheme, analogous to the set of reactions proposed
to occur during the thermal degradation of jet fuels (Coleman et al., 1992). It is
suggested that alkanes are first oxidized, and can subsequently form alkenes or
ketones. As shown in Fig. 6.9, catalytic dehydrogenation of alcohols occurs in two
ways depending on the presence or absence of oxygen (Haines, 1988). But reaction I
is favored at high temperatures. In pyrolysis experiments, very often the alkan-2-ones
are highest in concentration and often their predominance occurs together with
terminal n-alkenes, in agreement with the proposed mechanism.
CONCLUSIONS
Aliphatic ketones are commonly formed under reducing hydrothermal
conditions from alkenes, alkanes andlor aliphatic-rich sedimentary organic matter.
These results indicate that a high temperature chemical reaction is responsible is for
their formation. A mechanism is proposed where aliphatic alkanes and alkenes
proceed through an alcohol intermediate, which can then proceed to the ketone with or
without the presence of oxygen.
-
c,.,_L4
-
T4,d:-RI
Te1c. dc.' -
-
T 4id__.e
758
25:80
808
26:40
850
28:20
980
38:80
950
31:40
1808
33:28
Figure 6.1. Portion of a gas chromatogram showing the elution order of six C14
ketone isomers.
188.0
50.0
?-1'
108
280
150
258
38
100.0
50.0
PVE
c)
100.8
50.8
I.t
M/E
d)
55
1
183 197 212
I.J'I.I. I.I.1.p.I.I.i.l.
50
100
158
200
258
180
150
288
258
208
258
58
100.01
I
85
50.0
PI/E
71
I
58
71
100.0
4.
M'E
58
108
158
188.8
50.6
71
I
113
I
141 15
I
,II
I
tilE
50
1.1.1
180
'I
150
P14
159 183197 22
280
250
300
Figue 6.2. Mass spectra of aliphatic ketone standards ; a) tetradecan-2-one; b)
tetradecan-3-one; c) tetradecan-4-one; d) tetradecan-5-one; e) tetradecan-6-one; f)
tetradecan-7-one.
191
58
188.8
58.8
71
1
1
..,
.Ii
I
17
58
fi/E
1.4 169183197212
ii
F
I
I
I
I
I
I
I
I
I
I
I
I
J
I
250
208
150
188
ioo.o
72
1
50.0
183
95 109 123 138
I .ii A 'j
filE
50
169
1
194
258
200
150
180
212
71
100.0-
re-trrdec.....- a-e
58
86
58.8I
169
99
ii
ii
I,
M/E
I
50
ie
124
141
I
212
1R5
250
200
150
100
58
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71
-re *,dec
.i
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113 127
)1j,
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i
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183
I
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I
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58
180
158
288
258
Figure 6.3. Mass spectra corresponding to the peaks in Fig. 6.1.
C
92
6.4
z
the
fractl0
OiJ
the Ns0
'92..cft1 I1te.rjOr a) POlar
raoa
193
n-alkaries
16
15
j4
13
I
32
IT
I
18
I
I
I
'.24
I
11.26
12
a) Nonpolar Fraction
34
n-alkan-2-ones
it
U,
1,6
18'
20 22
jJjjJjjjjz
b) Polar Fraction
Time
Figure 6.5. Gas chromatograms of the H20 - n-C32H66 - Sulfide system (72 hr @
350°C): a) nonpolar aliphatic fraction and b) polar NSO fraction.
194
00
r.s.
LS.
LS.
T.c.
c)
I K
I. S.
A
4)
I K
IK
I
z.s.
I
Zo.
i
e)
IC
JLLJLLJLUJJ
Figure 6.6. Gas chromatograms of the poiar NSO fractions obtained by hydrous
pyrolysis of 1,1 3-tetradecadiene, 1 -hexadecene and eicosane on Messel shale: a) 1 hr
@ 330°C; b) 5 hr @ 330°C; c) 10 hr @ 330°C; d) 36 hr @ 330°C; e) 72 hr @ 330°C.
Internal standards: n-C24D50 and n-C32D.
195
18?.9-1
-Au--2-'
)
-c"C
t.il.___J
A'-''
948
31:20
920
30:40
988
30:00
880
29:20
860
28:48
848
28:00
828
27:20
I
I
I
I
'
800
26:40
\
211.2-i
)
A,r_c,-e
/
I
I
I
1040
1060
1880
34:40
35:20
36:88
1120
37:20
1108
36:40
1148
1160
1180
38:00
38:40
39:20
1568
52:08
52:48
273.6
- 3-,.-c
I
/
RIC
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I.
1448
1468
48:00
48:48
1488
49:20
1500
50:08
J\
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50:40
1548
51:28
1588
Figure 6.7. Reconstructed ion chromatograms (RIC) representative of the aliphatic
ketones generated during the molecular probe experiments pyrolyzed with Messel
shale: a) ketones from 1,1 3-tetradecadiene; b) ketones from 1 -hexadecene; c) ketones
from eicosane.
196
A(c.,-
I
108.
/ f,4(, (
1440
48:88
1460
48:40
1480
43:20
1580
50:88
1528
50:40
1540
51:28
1568
52:08
1580
52:48
Figure 6.8. Mass fragmentogram (mlz 57, 58, 71; 72) representative of the aliphatic
ketones present in a hydrothermally-derived oil (1972-CH1 Interior).
197
: L4,-'C
5
*
ø(_u_
/#._'
' ,-
----- -
-----
Z- t4-
OH-
In
cT
£eot1
Ii)
*
C)
Figure 6.9. Proposed reaction scheme for the generation of ketones during the
pyrolysis of aliphatic-rich organic matter.
CHAPTER 7
Conclusions
199
Hydrothermal alteration of sedimentary organic matter in the Guaymas Basin
transforms the insoluble organic matter into petroleum by high temperature aqueous
pyrolysis. The results obtained in this dissertation demonstrate the utility of applying
pyrolysis techniques such as hydrous pyrolysis and confinement pyrolysis to simulate
and study the organic geochemical processes occurring under extreme hydrothermal
conditions such as those found in the Guaymas Basin hydrothermal system. A survey
of the oils and sediment extracts from this system and the application of pyrolysis
techniques to duplicate the natural hydrous pyrolysis process has resulted in the
following:
several homologous series of aliphatic ketones were found to be
ubiquitous in the oils associated with high temperature hydrothermal
vents, and in the extracts of sediments that have been thermally altered
by sill intrusions, their smooth distributions indicate a pyrolytic origin;
novel isoprenoid phenols are the major compounds in the polar NSO
fractions of hydrothermal oils and their distributions indicate an origin
from natural product precursors in the sedimentary organic matter;
several series of alkylphenol isomers are present in the oils, their smooth
distributions indicate that they are hydrothermal synthesis products;
the rapid hydrothermal oil generation process at high temperature is
suited for simulation by pyrolysis methods such as hydrous pyrolysis;
a series of experiments using the hydrous pyrolysis technique resulted in a
re-evaluation of the Hoering (1984) paper, proposing a combination of
ionic and radical reactions to explain the extent of deuterium incorporation
observed when pyrolysis experiments are carried out in D20;
the application of a standard hydrous pyrolysis technique duplicated some
of the thermally-enhanced diagenetic conversions documented under
natural conditions;
200
evaluation of the hydrous pyrolysis technique indicated that mineralcatalyzed reactions may be preferentially decreased relative to the radical
cracking reactions when applying the method to the pyrolysis of
unconsolidated marine sediments;
the procedure of confinement pyrolysis was developed and successfully
applied to the simulation of catagenetic transformations occurring by
hydrothermal alteration;
reaction pathways were proposed to explain the origin of the aliphatic
ketones common in the hydrothermal oils.
The proposed reaction pathways presented in this thesis are based on both
experimental results and evidence reported in the literature. The hypothesized role of
clays as active sites for ionic chemistry is supported by numerous reports in the
literature on the catalytic effects of clay minerals. Further research into specific
reaction pathways of model organic compounds is required before conclusions can be
drawn about the relative contributions of ionic and radical reactions.
201
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APPENDICES
213
Appendix 1
The (;as Chromatograms for the Seabed Oils from the Hydrothermal Vents of
Guaymas Basin, Gulf of California
In this Appendix the gas chromatograms of the aliphatic , aromatic and NSO
fration' for the interior and exterior oils collected during the 1988 Alvin dive series are
pre.ented.
214
1972-CH1 Interior
215
1972-CH1 Exterior
216
1983-CH1 Interior
217
1983-CH1 Exterior
218
1984-CH1 Interior
219
1984-CH1 Exterior
220
1984-CH2 Interior
221
1984-CH2 Exterior
222
Appendix 2
The Gas Chromatograms for the Downcore Sediment Extracts from DSDP Site
477 of Guaymas Basin, Gulf of California
In this Appendix the gas chromatograms of the total extracts, aliphatic
aromatic and NSO fractions for the sediment extracts from DSDP Site 477 used in this
thesis are presented.
223
477-2-2 (145-150)
224
477-7-1 (88-90)
225
477-7-1 (106-108)
226
477-16-2 (140-145)
227
477-16-2 (145-150)
r
I.
Hi
228
477-16-4 (130-135)
229
477-16-4 (135-140)
230
477-17-1 (145-150)
231
477-19-1 (130-135)
232
477-19-1 (135-140)
33
234
477-21-1 (52-57 + 91-96)
fl
235
477-22-1 (110-115)
236
477-23-1 (90-95)
237
477-23-1 (CC)
238
Appendix 3
The Gas Chromatograms for the Downcore Sediment Extracts from DSDP Site
481A of Guaymas Basin, Gulf of California
In this Appendix the gas chromatograms of the total extracts, aliphatic
aromatic and NSO fractions for the sediment extracts from DSDP Site 481 A used in
this thesis are presented.
481A-4-2 (93-98)
481A-6-5 (118-120)
241
481A-6-5 (124-135)
n
r'
p
242
481A-7-6 (71-80)
243
481A-8-7 (top of pipe)
244
481A-12-4 (55-65)
245
F
481A-18-1 (30-32)
247
481A-18-1 (CC)
481A-20-1 (110-115)
J
fl
249
481A-22-1 (65-70)
250
481A-22-7 (top of pipe)
251
481A-22-7 (97-101)
252
481A-24-CC
253
481A-25-CC
254
48 1A-26-CC
255
Appendix 4
The (;as Chromatograms from the Pyrolysis Experiments on the North Rift
Surface Sediment and Downcore Sediments of DSDP Site 481A, Guaymas Basin,
Gulf of California
In this Appendix the gas chromatograms of the aliphatic , aromatic and NSO
fraction' of the unaltered sediment extracts and the pyrolyzed sediment extracts used in
Chapter 5 of this thesis are presented.
256
AII-112-29 PC-S
(Unaltered)
257
AII-112-29 PC-S
(24 hr at 330°C)
258
All-112-29 PC-5
(48 hr at 330°C)
259
AII-112-29 PC-5
(72 hr at 330°C)
481A-8-7 (top of pipe)
(Unaltered)
261
481A-8-7 (top of pipe)
(24 hr at 330°C)
262
263
481A-8-7 (top of pipe)
(72hr at 330°C)
264
265
481A-22-7 (top of pipe)
(24 hr @ 330°C)
266