Open-file Report 212
New Mexico Bureau of Mines
and Mineral Resources
Origin of the Riley travertine
as constrained by the clay mineralogy of
acid- and EDTA-insoluble residues
by
James M. Barker, Industrial Minerals Geologist
New Mexico Bureau of Mines and Mineral Resources
Socorro, NM
87801
January 31, 1984
Introduction
The Riley
limestone
County,
travertine
deposit
present
travertine
its
1).
of
the
varied
deposition
formation
Barker
(1983),
in Table
Barker
Kottlowski
supported
is
environments
possible
Riley
origins.
Aft.er
unpublished
references
states
the
that
sepiolite
clay
clay
Table
2, the
along
with
environments
minerals.
their
over
others.
covered
is
area
this
report
of
calcite
in
summarized
include
Massingill
The origin
(1977),
most
(pedogenesis).
depositional
can be used to constrain
over
300 published
and caliche,
fraction,
(attapulgite)
relative
(caliche),
work,
of proposed
reviewing
or absence
and
paper
deposit
Based on this
presence
widely
on this
1941).
travertine
mineral
clay
because
secondary
(1982),
(1940,
on calcrete
and palygorskite
other
and others
assemblages
of the
vary
Previous
in the
and Denny
The clay-mineral
the
is controversial
and pervasive
studies
of caliche
Socorro
Riley
pedogenesis
directly
Chamberlin
that
of the
calcrete).
bears
(1962),
residues
Opinions
(travertine),
Earlier
(1983),
investigates
deposition,
which
1.
paper
travertine
morphology.
(nonpedogenic
economic
origin.
Riley
playa-lacustrine
spring
This
its
and potentially
age in northwestern
insoluble
to constrain
highly
include
(Fig.
in the
The origin
of
an unusual
of Plio-Pleistocene
New Mexico
minerals
is
most
but
and other
of attapulgite
abundance,
favors
and
Goudie
frequently
(1972)
contains
may also
work
the
contain
summarized
and sepiolite
some depositional
in
M AUPN I T S
QUATERNARY
Piedmont slope deposits(ps)
Fanglomerate deposits ( f )
QUATERNARY-TERTIARY
Sonta Fe Group(QTsf1
upper(u)inpartcorrelative with Sierra Lodrones Fm. and
including Riley travertine ( t )
Popotosa Fm.(p)
MESOZOIC
Mesaverde Group
undifferentiated;
shole.siltstone,sandstone
c
Figure I . Generalized geologic map of
2
lhe
Riley lravenine and adjacent area.
3
_....
G.C.
Mssingill
(1977)
Age
1
- 3 my.
Plio-Pleistocene
1-3 m.y.
< 3.5 million
years
< late Pliocene
F.E. Kottlovski
(1952)
C.S.
Cenozoic
Quaternary
Denny
(1940, 1941)
t
e
I
S, A
I
I
I
!
A
A, S
Geographicandgeologicsetting
masses ( n o r t h mesa
The R i l e y t r a v e r t i n e o c c u r s i n t w o m a i n
a n ds o u t h
mesa) c e n t e r e da p p r o x i m a t e l y
a p p r o x i m a t e l y1 7
km s o u t h o f t h e
6.5 km west and
s u m m i t o fL a d r o nP e a ka n de a s t -
R i t a ) , N e w Mexico(Fig.2).TheRiley
southeaso
t fR i l e y( S a n t a
t r a v e r t i n e is i n t e r m i t t e n t l y e x p o s e d
by l o c a l e r o s i o n o f
o v e r l y i n gS a n t aF eG r o u ps e d i m e n t sa l o n gm e s ae d g e sf a c i n gt h e
Rio
Salado.
of n o r t h m e s a u n d e r l i e s a p p r o x i m a t e l y
The R i l e y t r a v e r t i n e
46km2
i n T. 2 N.,
R.
3 W. a n d T. 3 N. R.
a p p r o x i m a t e l y2 1
S.,
R.
2 W.,
k m 2 i n T. 1 N., R.
T. 1 S.,
it underlies
A t s o u t hm e s a ,
o ft h eL a d r o nM o u n t a i n s .
R.
3 W.,
S e v i l l e t a Game R e f u g eo nt h e
2
west f l a n k
3 W. o n t h e
w., T.
w., T.
1 N., R. 3
1
and a s m a l l p o r t i o n of t h e
west s i d e o f t h e S i l v e r
Creek
drainage.
i s v i ag r a d e dr o a d sf r o mM a g d a l e n a
Access t o t h e s t u d y a r e a
(US-60) o rf r o mB e r n a r d 0
( e x i t 175on1-25).
When d r y ,t h eR i o
S a l a d op r o v i d e ss e c o n d a r yf o u r - w h e e l - d r i v ea c c e s st ob o t hn o r t h
a n ds o u t h
mesas.
N o r t h mesa is a p p r o a c h e dm o s te a s i l yf r o mt h e
n o r t h o nr a n c hr o a d sb e a r i n gs o u t h e a s t w a r dt o w a r d st h ew e s t e r n
s l o p eo ft h eL a d r o nM o u n t a i n sf r o mt h ec o u n t yr 0 a . dt oR i l e y .T h e
s o u t hm e s a
i s r e a c h e dm o s te a s i l yf r o mt h eH u d g i n sR a n c hr o a d
w h i c hi n t e r s e c t s
m o s to fs o u t h
US-60 e a s t ofMagdalena.
A l l o fn o r t h
mesaand
mesa a r e o nt h eR i l e y1 5 - m i nq u a d r a n g l ew i t ht h e
r e m a i n d e ro nt h eM a g d a l e n a1 5 - m i nq u a d r a n g l e .P r e l i m i n a r y
m i nq u a d r a n g l e s
7.5-
are available.
T h eR i l e yt r a v e r t i n e
t h eS a n t aF eG r o u p( B a r k e r ,
is a r e l a t i v e l yu n d e f o r m e d
1983) d e p o s i t e db e t w e e n
member o f
1 and 3 m.y.
6
.
.
ago (Chamberlin and others, 1982).
It descends in elevation from
north mesa to south mesa and overlaps progressively younger
(Paleozoic, Mesozoic, and Cenozoic) units to the south.
The Riley travertine rangesfrom massive to laminar with
locally significant reworked, vuggy, algae-like, and fragmented
portions.
This varied morphology is interpreted by Barker (1983)
as follows.
The limestone is the result of a nonpedogenic
process producing proximal (surface and subsurface) and
distal (subsurface) secondary carbonate deposits
related primarily to lateral groundwaterflow. The
carbonate-charged water is interpreted to havebeen
generated in Paleozoic limestones on the west
flank of
the Ladron Mountains and the southeast flank of Sierra
Lucero in the late Cenozoic. These waters flowed over
and through alluvial fansand other sediments into and
down the axis of an elongatebasinor valleydraining
southward. This drainage merged with an east-trending
valley which drained eastward near the present latitude
of San Lorenzo Canyon and emptied into the ancestral
Rio Grande. Proximal spring, lacustrine, and reworked
carbonate deposits were formed at thesurface. They
are contemporaneous with pervasive
and expansive
subsurface secondary calcite cementation preof
existing host sediments. This depositional system is
analogous in part to the ground-water calcrete
(nonpedogenic) described in Western Australia by
several authors (see for example Carlisle and others,
1978).
This model should yield clay-mineral assemblages
that result from
the depositional environmentof the host sedimentary
rocks or
sediments and, therefore, that are varied.
In contrast, one mode
of formation wouldtend towards a single clay-mineralassemblage.
If the Riley travertine is a caliche, attapulgite should be
dominant over other clays.
If it is an alkaline lacustrine-playa
deposit, sepiolite should be dominant.
A
spring, fresh-water
lake, or pervasive secondary origin shouldyield detrital clays
--
such as illite, smectite, and kaolinite, typical for an arid
climate acting on a Paleozoic limestone substrate.
Sampling and experimental techniques
Seventeen samples of the Riley travertinewere collected in
March 1983.
Preliminary data, including clay mineralogy
of HC1 (10%) insoluble fractions, are published in Barker (1983).
Additional
work
was
done
in
gently derived insoluble fractions.
the
fall
of
1983
togenerate
These samples werepartially
digested using very dilute acetic acid followed by warm EDTA
solution.
The clay-size fractions of the insoluble residues were
then analyzed by X-ray diffraction (XRD) for clay and
detrital mineralogy.
Samples of the Riley travertinewere treated initially with
dilute (0.25 M) acetic acid as described by Ostrom (1961).
Because of the samples' high calcium carbonate content, this
p r o v e d t o o slow.
The
samples
werepurgedof
washing and decanting with deionized water.
E D T A w a s t h e n used
Fernalld (1973).
for
digestion
as
acetic by
acid
A 0.2 M solution of
described
by Bodine
and
This greatly sped up carbonate solution but at
much greater cost in reagents.
The EDTA procedure was modified
slightly as describedbelow.
Carbonate-solution procedures
Acetic-acid method--Samples of the Riley travertine
(approximately 150-gr) were scrubbed and washed thoroughly in
deionized water.
Then, they were crushed for 5 min in a Buehler
concentric-ring vibratory.crusher yielding avery fine carbonate
8
more
powder.Such
a f i n eg r i n du l t i m a t e l yc a u s e dp r o b l e m si nb o t h
d i s s o l v i n gm e t h o d su s e d ,b e c a u s e
much o f t h e c a r b o n a t e m a t e r i a l
b e g i n sa sc l a y - s i z ep a r t i c l e s .T h e s e ,p l u st h el a r g e rp a r t i c l e s
j u s t b e f o r ep a r t i c l e
d i s s o l v e di n t ot h ec l a y - s i z er a n g e
e x t i n c t i o n ,y i e l d i n gp e r s i s t e n tc l a y - s i z ec a r b o n a t er e s i d u e s
t h e X R D slides.
(1961) p r o c e d u r e is
T h i s c h a n g ef r o mO s t r o m ' s
is n o t p o s s i b l e
n o tr e c o m m e n d e ds i n c ec l a y - c a r b o n a t es e p a r a t i o n
is c o m p l e t e l yd i s s o l v e d .
u n t i la l lt h ec a r b o n a t e
on
I l e f tc o a r s e r
p a r t i c l e s ( l c m + ) t o i n s u r e t h a t c a r b o n a t e w a s a l w a y s p r e s e nst o
t h ea c i dw o u l db el e s sl i k e l yt oa t t a c k
t h e c l a y s .O s t r o m ' s
a -60 mesh g r i n ds h o u l db eu s e d ,b e c a u s e
(1961)recommendationof
t h er e l a t i v e l yc o a r s ec a r b o n a t ec a nb es e p a r a t e de a s i l yf r o mt h e
time d u r i n g t h e d i s s o l v i n g
liberatedclay-sizematerialatany
process.
A c e t i ca c i d ,m i x e dt o
0.25 M c o n c e n t r a t i o n ,w a sa d d e dt ot h e
samples,whichwerestirredperiodicallyuntilreaction
complete.
The s p e n ta c i d
was d e c a n t e d ,a n d
new
a
was
c h a r g e of 0.25
M a c e t i c a c i d a d d e d f o r a s many i t e r a t i o n s a s n e e d e d .
m a t e r i a l sa sr i c h
With
i n c a r b o n a t ea st h eR i l e yt r a v e r t i n e ,d o z e n so f
c h a r g e so fa c i dw o u l db en e e d e da tt h e0 . 9 - l i t e rc h a r g es i z e
utilized.
T h u s , a n EDTA-based p r o c e d u r ew a si n i t i a t e dp a r t
way
t h r o u g ht h es a m p l e - d i s s o l v i n gs t a g e .
EDTA m e t h o d - - C h e l a t i o n o f c a r b o n a t e
e t h y l e n e d i a m i n et e t r a c e t i ca c i d
by t e t r a s o d i u m
(EDTA) a f f o r d s a methodof
c a r b o n a t es o l u t i o nt h a td o e sn o ta f f e c to r i g i n a lc l a ym i n e r a l o g y .
T h em e t h o dd e s c r i b e d
Basedon
t h e i rc h a r t s ,
byBodineandFernalld(1973)wasused.
a 0.2 M EDTA s o l u t i o n( 7 5
9
gm t e c h n i c a l -
grade disodium EDTA in 1 liter deionized water at pH 12.5) was
applied to the ground carbonate partially digested by acetic
The solution was heated to90° C for 6 0 to 9 0 min using a
acid.
continuous magnetic stirrer.
After settling and decanting, a new
charge of EDTA was added until the carbonatewas entirely
chelated.
The problems caused by the very fine grind as
described above were also present in this procedure.
After dissolution, decanting, and deflocculation, using
deionized water only, the clay fraction was separated from the
coarser insoluble particles.
Standard clay-mineralogy techniques
were then used as follows.
Following deflocculation, the dispersed clay
was left
undisturbed for 10 min.
Then, eyedropper charges of the
suspension were collected carefully from the topmostsurface and
deposited on glass slides until they were fully covered.
Four
slides of each sample were prepared as described above and then
allowed to air dry overnight.
The oriented slides thus derived
are not useable for quantitative work
because of size
fractionation in the suspension columnduring drying.
The larger
kaolinites settle out first
and then are masked somewhat
by later
mantling by the slower-settling smaller clayssuch as srnectite or
illite.
The
slides
38O to 2O02
and a second
.
were
runon
a diffractometer a t 2 O
28/minfrom
The slide was thenglycolated at 60° C for 3 hrs
run
was
made
as describedabove.
then heated to approximately300-330°
C
Theslides
were
(some to 390° C) for 1 hr
and run hot as described above, except thespan was shortened t o
15O-Zo
20.
Controlled-humidity and cation-saturation runs were
10
not done.
Clay-mineral reactions during carbonate solution
Two problems possibly developed using the acetic-acid or
EDTA digestion techniques.
as
These are destruction of clays, such
illite or smectite, by excess acidity and the alteration of
attapulgite-sepiolite by either excessively acid or basic
conditions.
The work by Ostrom (1961) in proving his technique showed.no
alteration in acidic solutions (if less than 0.3 M) for randomly
interstratified illite-montmorillonite, chlorite, illite, or
kaolinite.
He did not include attapulgite or sepiolite.
Carroll
(1970, pp. 43-44) states that attapulgite and sepiolite require
alkaline conditions for survival
and that they are decomposed by
acid and won't survive below pH 7 .
the threshold.
Other workers suggest pH 3 as
In addition, Khoury, et al. (1982) predict that
"
chlorite will forminstead of attapulgite-sepiolite at high pH
and high Mg and/or Al.
This prediction is based on their
interpretation of the work of Siffert (1962, in Khoury et al.,
"
1982), who found that sepiolite precipitates at pH8.5,
trioctohedral smectite (mixed-layer kerolite-stevensite of Khoury
et al.,
-~
1982) at pH 8.5-9,
at pH above 9.
and talc plus trioctohedral smectite
The EDTA solution used has a pH of approximately
12.5, which is possibly high enough to alter sepioliteattapulgite to mixed-layer kerolite or stevensite (chlorite) plus
talc (Ebrl,et al., 1982).
The
XRD
data
suggest
that
no
"
conversion occurred during digestion of the Riley travertine
since neither kerolite, stevensite,or talc were detected.
11
such
Bodine and Fernalld (1973) evaluated the effects of EDTA
treatment on clayminerals.
They found no significant alteration
occurred with treatment times under 4 hrs.
They examined
chlorite and illite (mixture), montmorillonite, and kaolinite.
They did not determine effects on attapulgite-sepiolite.
Glover
(1961) implied that EDTA treatment was less destructive than
acid
treatment where clays wereinvolved, but he studied no clays
individually.
Hill and Runnels (1960) made a similar Suggestion.
The original digestion using 10% HC1 (Barker, 1983) produced
clay-size residues containing kaolinite, illite, and smectite in
order of decreasing abundance (Table 3).
Treatment with this
concentrated a solutionof HC1 probably biased the clay data so a
less chemically harsh dissolution technique was
used for this
study.
The presence
01:
absence of attapulgite or sepiolite is
significant in the identification of depositional environment,
and the HC1 technique might have removed or altered
them.
Clay-mineral analysis
The clay size fraction of the insoluble residues from eight
samples
ofRiley travertine were analyzed by X-ray diffraction
techniques.
The samples were deflocculated by repeated rinsings
with deionized water and 10-min centrifugation cycles. No
deflocculating chemicals were used.
Standard oriented slides were prepared by sedimentation
(Stokes Law) techniques with their inherent bias (Stokke and
Carson, 1973; Gibbs,,1965, 1968).
This bias precluded meaningful
measurement of clay-mineral percentages, and many of the illite
curves are masked by mixed-layer clays.
12
Thus, the following
analysis is based on the presence or absence of significant clays
rather than on relative abundance.
The
XRDanalysis
was
done
a Rigaku
on D-Max.
copper fine focus at40 KV and 25 ma.
Settings
Slits were lo divergence,
lo scatter, 0.3O receiving, and 0.3O monochromator.
was
run
untreated
were
followed
by aglycolated
run
Each sample
and
heated
(300° C
and/or 390° C) runs.
Results
The mineralogy of the clay fraction,
based on number of
occurrences in the samples and in decreasing order is as follows:
-
quartz
feldspar (Na-Ca-K combined)
kaolinite
- illite
- mixed-layer
-
illite smectite (randomand ordered)
rhodochrosite
amphiboles
zeolite (clinoptilolite)
vermiculite (masked)
chlorite (masked)
smectite (difficult to identifyas mashed)
superlattice clay or ordered mixed-layer
(vermiculite-illite)
This is the mineralogy derived from acetic-acid/EDTA
insoluble residues.
In contrast, the harsher HC1-derived'
insoluble residues have a much
simpler mineralogy in their claysize fraction, as shown below:
13
Sample
1
Quartz
Plagioclase
K-spar
Hb
Kaolinite
Illite
Calcium
Smctite
~~~~~
4
+
0
0
0
+
0
tr
RTB 12
0
0
tr
tr
0
0
0
RTB 13
+
+
+
+
+
tr
0
0
0
0
-
0
+
tr
0
0
0
0
0
RTB
RTB 14
RTB 15
Symbol
Relative abundance
+
-
major
minor
absent
trace
0
tr
Source:
Barker,
Table 3.
Cu f i n e f o c u s
KV = 40, ma = 25
K-spar = potassium feldspar
Hb = hornblende
1983
Q u a l i t a t i v e X-ray d i f f r a c t i o n a n a l y s i s of t h e f i n e f r a c t i o n
(-230 mesh) of selected samples of t h e R i l e y t r a v e r t i n e
t r e a t e d w i t h 10% HC1. The clay peaks were very small
except for kaolinite.
14
-
quartz
feldspar
kaolinite
illite
-
amphibole
-
smectite
The minerals described below are from the EDTA/acetic-acid
procedure. Each
mineral is described by characteristic and
common peaks seen in the samples.
Quartz
Quartz is identified by its characteristic peak at
approximately 26.7O 2 9.
A
common peak also occurs at
approximately 21° 2 9 with some variability.
Feldspar
The feldspars occur from 27.5O 2 8 to 28.1°
29
with some
variation depending on potassium, calcium, and sodium content.
The
various
feldspars
were
not
differentiated.
I
Kaolinite
Kaolinite is found in 85% of the samplesexamined.
around 12.4O 2 9
, 20.5O(+)
28
, and
24.9O 2 9
Peaks
are typical.
Kaolinite is a very stable clay so it is least affected by acid
or EDTA techniques and,thus, is dominant in both suites of
analyses.
Illite
Illite is as common as kaolinte(85% of samples), but its
main
peak
at
9 is masked by the
approximately 28-80
illite-smectite mixed-layer "bump".
broad
Illite in untreated slides
is typically represented by a "shoulder" on the mixed-layer
15
Sample Clay
Number
K
I
S
C
V
M
+
?
+?
+?
5
+
-
-
?
0
I
+ +
?
8
+
+
9
+
11
+
L
SL
Remarks
minerals
Q
F
A
Z
R
+(nr) ? 0
+
+
-
0
+
+?
+(nr)? 0
+
+
+
o
n
0
0
+(r)
0
+
+
-
0
+
?
0
0
+(r)
0
+
+
0
+
0
+
?
+
0
+(r)
0
+
+
+
0
0
0
0
+
-
tr
+
0
tr
venniculiteillite superlatice
12
t r 0
0
0
0
0
0
+
tr 0
0
tr
virtually no
clay minerals
13
0
tr ?
0
0
+(r)
0
+
+
0
+
4
I
Other
minerals
I
I
0
+
0
t
no
heated
run
r
1
? cannot be differentiated
K = kaolinite
+ present
1 = illite
s = smectite
- trace
C = chlorite
0 absent
V = vermiculite
ML = mixed-layer illite-smectite (random
= r, ordered = nr)
SL = superlattice vermiculite-illite(?)
Q = quartz
A = amphibole
R = rhodochrosite
F = feldspar
Z = zeolite (probably clinoptilolite)
Table 4. Qualitative X-ray diffraction analysis of the acetic-acid/
EDTA insoluble residues of selected of
samples
the Riley
travertine.
curve, which separates somewhat upon glycolation.
The illite
peak is greatly sharpened and enhanced by heating of slides
because of recrystallization of the mixed-layer clay.
Mixed-layer Illite-Smectite
Mixed-layer
bumpbetween
clays
% ofthesamples
occur 7 0in
approximately3 O 2 8 and go 28.
This
aas broad
rangevaries
and usually includes a masked illitepeak and often a masked
vermiculite-chlorite one as well.
The mixed-layer clays are
frequently random, but one possible instance of an ordered mixedlayer clay was observed in sample 4.
However, this could also be
interpreted as a vermiculite o r chlorite peak.
Sample 4 has no
heated run because of slide disintegration; consequently, a
definitive answer is not possible.
The broad mixed-layer peak
shifts to a lower 2 8 upon glycolation (lattice expands).
Rhodochrosite
Rhodochrosite (MnC03) is found in 85% of the slides, usually
in trace amounts.
It is recognized by a sharp peak at
approximately 31.4O 2 8.
The Riley area is noted for high
manganese values including aonce-active mine at north mesa.
The
probable source rocks in the Paleozoic carbonatesalso have
appreciable amounts of manganese (Table 5).
Four samples with
peaks at 31.4O 2 8 were analyzed for MnC03 (Table 6).
Measurements range from a trace to 0.25% manganese.
Given the
abundance of manganese and the close relationship between calcium
and manganese carbonates, the presenceof rhodochrosite is not
unusual.
Rhodochrosite is soluble in HC1, so it did not appear
in the hydrochloric-acid treated samples (addendum 1).
17
.
...
+sal, 1*t€d
.
w
2.20
0.47
14.47
16.27
,1.14
0.96
2.03
5.74
.4.11
6.32
8.26
97.80
99.53
85.53
83.73
98.86
99.04
97.97
94.26
95.89
93.68
91.74
M
10.01
12
mssive,
recrystell.
mssive, saw
13
recrystal.
M
2.43
calrrete not Riley traverine 21.07
RTB 1
2
3
4
,:
mss. to la. M
mssive
91
5 . laminated
5a
l&ted
w
M
6
7
laminatel.
??4
mssive
missive
N4
.
8
9
10
14
15
16
18
LAD 7
9
12c
12d
M
crulely1aminatEd
travertine facies
11
MATB
'
upper mdSs1ve
middle.
...
..
EM
-. .
.
-
92.15
97.89
87.66
79.16
36.9
39.2
35.1
31.7
0.26
0.23
0.27
0.39
1300
639
583
278
92.40
95.65
37.0
38.3
0.23
0.22
528
635
91.64
39.1
0.30
757
1483
775
e57
490
1087
1099
933
710
' 857
1083
1099
89.99
96.89
38.8
0.33
462
97.57
78.93
72.66
70.96
95.42
87.61
99.a
39.9
0.22
416
64.93
83.66
93.40
26.0
33.6
37.4
0.38
0.38
0.34
34
81
53
35
6
7
6
6
<30
117
23
5
5
(30
t30
150
7
<30
608
78
8
(30
555
1123
5
32
488
114
4
331
373
233
e4
6
56
7
28
35
<30
6
30
'
~~
-I
'
mssive
91
mssive, r e v s t .
mssive
91
mssive
SM
%
27.34
29.04
4.58
12.39
569
G-mkerlin et al.1982 M
alalhrlin e t al.1982 w
Qlambeelin et al.1982 M
chanberlin et al.1982
travertine, Lucero
>20
.20
20
>20
w
0.91
99.09
98.39
39.4
3%
318
(300
0.15
0.3
0.2
0.5
1500
0.27
37
471
500
1000
700
617
759
1,339
759
99.46
40.04
0.13
'
+23.2
ffi.8
ffi.2
+7.0
i0.6
Amphibole
I did not
differentiate
the
various
peaks
from
1l0 210
8
to
but rather assigned them to the general class
of amphiboles.
Depending on composition, a range of peaks is possible, and the
varied lithologies of provenance areas open possibilities
beyond
the scope of this paper.
Zeolites
A strong peak at 9.8O
indicates clinoptilol'ite.
2e
with a secondary peak at 22.3O 2 8
The presence of a zeolite in 25% o f
the samples is not unexpected, since these are very common
sedimentary minerals in arid terranes.
Zeolites form generally
in alkaline ground-water conditions or in igneous rocks.
Clinoptilolite is more indicative of a sedimentary origin but may
be diagenetic on a small scale
rather than representing largescale alkaline conditions.
Vermiculite-Chlorite
Vermiculite (sample 5) or chlorite (sample 9) is indicated
by a peak at 6.3-6.5O
2 8.
Neither was affected by glycolation,
but, in one instance, the peak disappeared upon heating
(vermiculite) but did not in the other (chlorite).
Smectite
Smectite
may
be
present aas
distinct
phase
is m a s k e d b y
but
the broad mixed-layer illite-smectite peak.
-
Super lattice Clay
One
sample
showed
a broad
peak
at
3.8O 2 8 and a multiple
at
7.6O 2 6 , which, when converted to d-spacing, yielded a clay most
likely made up of vermiculite-illite.
This clay did not expand
much upon glycolation nor contract much upon heating
(from 23O 2 8
19
Sample
Number
Remarks
4
5
11
12
I
Table 6.
Manganese
Percent
0.025-0.125
trace
trace
0.05-0.25
massive facies, south mesa
laminated facies, north mesa
massive facies, some
recrystallization, north mesa
Semiquantitative X-ray fluorescence analysis of
manganese content of Riley travertine samples with
a
31.5O 2 8 (rhodochrosite).
to 20.50 2 e to 2 2 0 2 8 1.
Discussion
The data for the HC1 digestion are in Table
3, and the data
for the acetic-acid/EDTA digestion are in Table 4.
The XRD plots
are in addendum 1 (HC1) and addendum 2 (acetic acid-EDTA). X-ray
fluorescence (XRF) plots of selected samples for their manganese
content are in addendum 3.
Glass and others (1973) and Frye and others (1974, 1978)
studied the Ogallala Formation in eastern New Mexico.
The
general regional geology is similar to that of the Riley
travertine area.
Both are underlain by Permian and Triassic
rocks, often with identical units.
The clay minerals they
assigned to a "normal" detrital assemblage from such basement
rocks were smectite, illite, and kaolinite.
This assemblage is
basically the same as that
found in the Riley travertine
insoluble residues.
Based on this association, the Riley
travertine has only a detrital claycomponent.
Attapulgite and sepiolite were not detected in
the Riley
travertine.
The data in Table 2 can be used to differentiate the
occurrence of attapulgite and sepiolite.
to be mutually exclusive.
These two minerals tend
However, they often occur together
during a transition, and this mixture represents slightly
varying
conditions at the interface between the stability fields for
each.
Universal requirements for both attapulgite
and sepiolite
are relatively dry or dessicating conditions.
The chemistry of
these minerals requireshigh silica, high Mg, and high (but
21
restricted) pH.
Table 5 shows the high Mg content of the
regional carbonates.
Ishphording (1973) has shown that
attapulgite additionally requires high aluminum.
sepiolite occurs under drier conditions.
Climatically,
Attapulgite has much
greater resistance to weathering than sepiolite.
Attapulgite is
usually sedimentary, whereas sepioliteis sedimentary but also is
common in igneous association.
Since both require high
magnesium and alkalinity, conditions may not havebeen correct.
However, Glass and others (1973) and Frye and others (1974, 1978)
found abundant attapulgiteand sepiolite in certain facies
dependent on environment.
So
attapulgite and sepiolite do occur
in eastern New Mexico where source
rocks and climate are very
similar to northwestern Socorro County.
Thus, the lack of
attapulgite and sepiolite in the Riley traverinte must be related
to factors other than lack of magnesium,
low alkalinity, etc.
since they formed in eastern New Mexico under similar
conditions.
The variable seems to be the environment ofdeposition.
is
Attapulgite is primarily associated with soils while sepiolite
more common in alkaline lakes or playas (Table 2).
Apparently,
these environments were not present during formation
of the Riley
travertine, which is thus neither asoil nor an alkaline
lacustrine deposit.
This conclusion is in harmony with recent
work (Barker, 1983).
The main 2-8 peaks for attapulgite (A) and sepiolite ( S ) are
as follows:
A
8.4*(10)
13.75(3)
S
7.3*(10)
11.91(2)**
19.86(4)**
27.61(3)**
35.19(3)
19.77(3)** 20.60(2)** 26.52
22
(2)**
*
**
key line
usually masked in Riley samples
(relative intensity)
The 10-intensity peaks are maskedby the broad mixed-layer illite
zone.
In addition, many of the secondary peaks are maskedby
I
I
various other clay and nonclay minerals.
Thus, a small amount of
I
attapulgite
i
I
or sepiolite could be present and missed.
the basis for assigning a pedogenic
OK
However,
alkaline lacustrine
environment to the Riley travertine
is based on attapulgite or
sepiolite dominating the claymineralogy.
Minor amounts of
attapulgite and sepiolite overwhelmedby illite, smectite,
kaolinite, etc. is nondiagnostic.
that
the
Riley
For these reasons, I conclude
travertine
was
not
formed
a soil
or
as
as
an
alkaline lake-playa deposit.
The illite-smectite-kaolinite suite does not define
other
environments conclusively.
Therefore, the Riley travertine could
be a spring deposit or a pervasive secondary carbonatedeposit.
The detrital clays couldbe deposited in a travertine during its
deposition either by wind or, as circumstances permit,
by fluvial
activity. In contrast, during pervasive carbonate deposition, the
clays are an artifact of the depositional environmentthe host
sediments represent.
Carbonate crystallization can destroy some
silicates (including clays),
so
the initial host clay mineralogy
cannot be known with certainty.
Summary
The origin of the Riley travertineis constrained by the
absence of attapulgite and sepiolite.
These clay minerals are
associated with soils (caliche-calcrete) and alkaline lakes,
23
respectively, so the probability that these are
the depositional
environments for the Riley travertine
is low.
The clay-mineral assemblage present is a typical detrital
one for areas of New Mexico with
Permian-Triassic bedrock.
The
vermiculite, chlorite, illite, mixed-layer illite-smectite, and
kaolinite are not diagnostic
and may represent either syngenetic
minerals in a spring depositor minerals representative of the
host-rock depositional environment if a pervasive calcite origin
is correct.
The presence of vermiculite and chlorite is uncertain
pending more detailed sampling.
Because of the preliminary natureof this report, some
additional work mustbe done to confirm the conclusions
reached.
Additional work includes, but may not be limited to, the
following:
Dissolve by EDTA a calcareousrock with attapulgite
and sepiolite as a control for the above
experiments.
Redissolve all the Riley travertine samples using EDTA
in the
alone to eliminate possible problems inherent
acetic-acid procedure.
3
The clay-size fraction should be further sized and
scanning-electron micrographs should be made of a
fraction appropriate to detect acicular attapulgite
and/or sepiolite.
4)
A recent calichefrom the Riley area should be analyzed
for attapulgite and sepiolite
to see if they are forming
under present conditions.
This could include secondary
carbonate material fromcase-hardened portions of the
24
Riley travertine.
Drill cores of the Riley travertineare in hand, and
deeper portions shouldbe analyzed as described earlier
to eliminate any overprint in clay mineralogy from
collecting near-surface samples.
Undertake additional detailed geology including dating,
mapping (geologic and facies), thin-section analysis,
and detailed sampling.
Acknowledgments
All the ideasexpressed and the conclusions reached in this
report
are own.
my
My
colleagues
at
the
New
Mexico
Bureau
Mines and Mineral Resources were a great
help in various portions
of this study.
In particular,I thank G. S. Austin, J. Renault,
J. Love, R. M. North, K. B. Faris,
and contributions.
andP. Cooksey
for
their
time
Technical assistance was supplied by M.
Bowie, B. Casselberry, and J. Hintgen.
References
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1983, Preliminary investigationof the origin of
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Mexico Geological Society Guidebook to 34th
Field Conference,
pp. 269-276.
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of gypsum, anhydrite, and Ca-Mg carbonates: Journal of
Sedimentary Petrology, v. 43, no. 4, pp. 1152-1156.
Carlisle, D., and others, 1978, The distribution o f calcretes and
gypcretes in southwestern United States and their uranium
favorability based on deposits in western Australia and
southwest Africa (Namibia): U.S. Department of Energy,
Open-file Report GJBX-29(78), 274 pp.
Carroll, D., 1970, Clay minerals--a guide to their x-ray
identification: Geological Society of America, Special
25
of
P a p e r1 2 6 ,7 9p p .
C h a m b e r l i n , R. M., a n do t h e r s ,1 9 8 2 ,P r e l i m i n a r ye v a l u a t i o no ft h e
m i n e r a lr e s o u r c ep o t e n t i a lo ft h eS i e r r aL a d r o n e sW i l d e r n e s s
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t h eS a nA c a c i aa r e a
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i
n
n
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r
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r
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n
d
c
l
a
y
m
i
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c e n t r a l - e a s t e r n N e w Mexico:
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of Sedimentary
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G l o v e r , E. D., 1 9 6 1 ,M e t h o do fs o l u t i o no fc a l c a r e o u sm a t e r i a l
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Goudie, A., 1 9 7 2 C
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4 , pp.449-463.
W. R., J r . , a n dR u n n e l s ,
R. T., 1 9 6 0 ,V e r s e n e ,
a ndw t o o l
f o rs t u d yo fc a r b o n a t er o c k s :A m e r i c a nA s s o c i a t i o no f
P e t r o l e u mG e o l o g i s t sB u l l e t i n ,
v. 44, pp., 631-632.
Isphording,
W.
C.,
1 9 7 3 ,D i s c u s s i o n
26
of t h eo c c u r r e n c ea n do r i g i n
o fs e d i m e n t a r yp a l y g o r s k i t e - s e p i o l i t ed e p o s i t s :C l a y sa n d
C l a yM i n e r a l s ,
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K h o u r y , H. N., E b e r l , D. D., a n d J o n e s ,
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C l a y Minerals, v.30,no.5,pp.327-336.
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v. 3,no.
4 , pp.957-964.
27
x-
Addendum 1
XRD Data on HC1-derived
Insoluble Residues of Riley Travertine
Samples
a
a
a
29
30
e
e
e
e
e
e
34
a
e
a
35
36
38
Addendum 2
XRD Data on Acetic Acid/EDTA
Derived Insoluble Residues of
Riley Travertine Samples
39
40
41
!
I
0
0
44
0
0
45
49
I
.t
-
? :>
52
53
54
e
e
e
57
a
a
e
62
63
e
e
a
69
70
Addendum 3
XRF DataonManganese
C o n t e n t of some R i l e y T r a v e r t i n e
Samples
a
'
72
'., .
..
, I
r: 4.
.~.
-
-.
-
"
-
Rigaku Part No. KC-01
e
,
e
. .
e
-
75