ORIGIN AND MATURITY OF THE ORGANIC MATTER IN THE MUD
BRECCIA FROM “ANAXIMANDER” MUD VOLCANOES, EASTERN
MEDITERRANEAN
N. PASADAKIS, E. MANUTSOGLU
Technical University of Crete, Mineral Resources Engineering Department,
University Campus,
73100 Chania, Greece
Abstract
In
this
work
standard
geochemical
procedures
were
applied
to
characterize the organic matter content from four cores samples,
covering the upper 70cm of the sea bottom sediments. Three of them
were collected from the “Amsterdam” mud volcano sediments and a forth
one from the “Kazan” mud volcano in the “Anaximander” area (Eastern
Mediterranean). TOC, elemental analysis, Rock-Eval pyrolysis, isolation
of the extractable organic matter and routine biomarkers analysis were
employed. The experimental analytical results revealed a mixed origin of
the organic matter. Indications of organic material with minor diagenetic
alterations, as well as indications of thermally mature constituents were
found. Fingerprint of terrigenous origin was also identified. Differences in
the organic matter composition were observed between the two areas
under study. The obtained results are in agreement with geochemical
findings derived from other mud volcanoes previously studied in
Mediterranean Sea.
Geologicall setting
Samples and methods
The samples under study (Table 1) were collected during a site survey in
October 2004 on board of R/V Aegaeo from mud volcanoes areas in
Eastern Mediterranean (Anaximander project, EC contract EVK3-CT2002-000068). All samples were retrieved from the upper 70cm layer of
sediments and were stored under refrigerated conditions (4oC). The
contained water found to be ~30% w/w, determined by freeze-drying
prior to the subsequent analyses.
Table 1: Sediment samples analyzed during this study
Sample
φ
λ
Sampling
Area
Depth (m)
Α
35025’ 912
30033’ 691
Gravity core
Kazan M.V.
1693
Β
35019’ 990
30016’ 292
Gravity core
Amsterdam M.V.
2030
C
35020’ 000
30016’ 272
APCA core*
Amsterdam M.V.
2030
D
35020’ 001
35016’ 276
Box core
Amsterdam M.V.
2030
*
Core
Total carbon as well as total organic carbon after the removal of
carbonates by Hcl treatment were determined using a Euro 3000
elemental analyzer (Eurovector). The Rock-Eval analysis was carried out
on a Delsi Instruments R-E II system.Quantities (~3g) of each dry
sediment sample, after the addition of internal standard (19μg of n-C38)
were
ultrasonically
extracted
using
CHCl3-MeOH
(3:1
v/v).
The
extraction was repeated six times using 3ml of solvent mixture in each
step. The obtained extracts, after preconcentration, were separated into
two fractions, using open column chromatography on 5% activated silica
gel. Hexane and hexane-toluene (4:1 v/v) were used to elute non-polar
and polar fractions respectively. The non-polar (saturates) fractions were
further
analyzed
using
gas
chromatography
(GC)
and
gas
chromatography-mass spectrometry (GC-MS) techniques. Components
were identified based on the retention times of n-alkanes, as well as on
their mass spectra.
Results
The obtained experimental results are summarized below.
Table 2: Measured geochemical parameters
Sample
Total C (%)
TOC (%)
Saturates content
μg/g sediment
Α
1.720
0.51
49
Β
4.066
0.58
217
C
4.594
0.94
203
D
3.896
2.12
103
Table 3: Measured Rock-Eval parameters
Sample Tmax S1
S2
S3
S2/S3 HI
OI
Α
413
0.06 0.06 0.32
0.18
11.85 63.20
Β
421
0.06 0.13 0.41
0.32
22.34 70.46
C
425
0.07 0.16 0.66
0.23
16.50 69.73
D
420
0.23 0.10 0.50
0.19
4.49
23.38
Figure 2. Concentration profiles of normal alkanes (μg/g sediment)
determined from the GC analysis of the saturated fraction
Sample A
ug/g
1,5
1
0
C14 C15 C16 C17 Pr
C18 Ph C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33 C34 C35 C36 C37
Sample B
6
ug/g
4
2
0
C14 C15 C16 C17 Pr
C18 Ph C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33 C34 C35 C36 C37
Sample C
ug/g
10
5
0
C14 C15 C16 C17
Pr C18
Ph C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33 C34 C35 C36 C37
Sample D
ug/g
4
2
0
C14 C15 C16 C17 Pr
C18 Ph C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33 C34 C35 C36 C37
Figure 3. m/z 191 fragmentograms of the saturated fraction
A1 _SA_ 30
43 .7 43
10 0
42 .3 93
50 .8 78
45 .5 27
%
46 .0 94 48 .0 78
40 .1 92
51 .3 95
52 .6 79
39 .5 26
56 .4 4
37 .5 42
33 .6 58
0
B1 -S-2PP
42 .4 43
10 0
43 .8 43
40 .2 59
39 .5 76
38 .1 92
%
23 .6 22
31 .0 90
33 .7 41
45 .3 60
0
C 1-S61 2
42 .3 93
10 0
43 .7 94
42 .3 43
%
44 .5 11
40 .2 43
39 .5 76
23 .5 72
46 .1 28 48 .0 28
31 .0 91
50 .8 96
52 .2 46
56 .3 8
0
D 1_ 2PP_S
42 .4 43
10 0
%
43 .7 94
44 .4 77
40 .2 43
46 .1 11
39 .5 42
31 .0 74
23 .4 05 24 .1 55
0
15 .0 00
17 .5 00
20 .0 00
22 .5 00
25 .0 00
28 .8 73
27 .5 00
30 .0 00
33 .6 74
32 .5 00
36 .2 92
35 .0 00
48 .0 78
50 .8 95
52 .2 46
37 .7 25
37 .5 00
40 .0 00
42 .5 00
45 .0 00
47 .5 00
50 .0 00
Discussion
TOC values measured are of the same magnitude compared to analogous
from other hydrate bearing sediments reported in the literature[1].
The concentration of individual n-alkanes varies significantly between
samples derived from different sites. Our findings for the Kazan M.V.
sample are in agreement with previously reported results [2]. The GC
traces of the non-polar fraction of the samples B and D exhibit fairly
similar unimodal distribution of n-alkanes centered on C26-C27 carbon
number. On the contrary sample A exhibit a bimodal distribution with
relative high concentrations of the C35-C37 alkanes. The apolar fraction
52 .5 00
56 .4 6
55 .0 00
5
of sample C shows a unimodal n-alkanes distribution with higher
concentrations of the lighter C17-C25 hydrocarbons compared to the B
and D samples. A UCM peak around C30 can also be observed in
samples B and D, which is absent in the samples A and C.
The observed odd-to-even predominance especially in the C27-C33 range
indicates a terrestrial input of the organic matter.
The calculated CPI indices are very low compared to the typical values
reported for recent sediments. It can be explained as an indication of
mixing with more mature organic matter. Similar mixing has been
reported in the Napoli mud volcano [3].
The steranes concentration found to be higher than the respective one of
hopanes, indicating significant microbial conrtibution in the organic
content of the sediments.
The determined S1 values are extremely low indicating the absence of
low hydrocarbons. S2 values are also of the same megnitude. The
measured low Tmax values indicate immature organic matter, relative
high oxugen content can be attributed to a possible terrestrial input.
References
[1]
A. Waseda A. and T. Uchida, 2005. “Organic geochemistry of gas,
gas hydrates and organic matter from JAPEX/JNOC/GSC et al. Mallik
gas hydrate production research well; in Scientific Results from the
Mallik 2002 gas Hydrates Production Research well Program, Mackenzie
Delat Northwest Territories, Canada, (ed.) S.R. Dallimore and T.S. Collett;
Geological Survey of Canada, Bulletin 585, 11p.
[2]
H.-M. Schulz, K.-C. Emeis, N. Volkmann. “Organic carbon
provenance and maturity in the mud breccia from the Napoli mud
volcano” Indicators of origin and burial depth” Earth and Planetary
Science letters, 147 (1997) 141-151.
[3]
J.P. Werne, J.S. Sinninghe Damste. “Mixed sources contribute to
the molecular isotopic signature of methane-rich mud breccia sediments
of Kazan mud volcano (eastern Mediterranean” Organic Geochemistry, 36
(2005) 13-27.