NOTICE CONCERNING COPYRIGHT
RESTRICTIONS
This document may contain copyrighted materials. These materials have
been made available for use in research, teaching, and private study, but
may not be used for any commercial purpose. Users may not otherwise
copy, reproduce, retransmit, distribute, publish, commercially exploit or
otherwise transfer any material.
The copyright law of the United States (Title 17, United States Code)
governs the making of photocopies or other reproductions of copyrighted
material.
Under certain conditions specified in the law, libraries and archives are
authorized to furnish a photocopy or other reproduction. One of these
specific conditions is that the photocopy or reproduction is not to be "used
for any purpose other than private study, scholarship, or research." If a
user makes a request for, or later uses, a photocopy or reproduction for
purposes in excess of "fair use," that user may be liable for copyright
infringement.
This institution reserves the right to refuse to accept a copying order if, in
its judgment, fulfillment of the order would involve violation of copyright
law.
Geothermal Resources Council, TRANSACTIONS, Vol. 8, August 1984
POSSIBLE RELATIONS BETWEEN ANOMALOUS SPRING WATER CHEMISTRY I N THE STILLWATER
RANGE AND THE DIXIE VALLEY GEOTHERMAL SYSTEM, NORTHERN NEVADA
BURKHARD BOHM
DESERT RESEARCH INSTITUTE
UNIVERSITY OF NEVADA SYSTEM, RENO, NEVADA
v a l u e s f a l l w i t h i n t h e 14 to 68 p e r c e n t i l e ,
s u l f a t e w i t h i n the 7 8 to 89 p e r c e n t i l e and
b i c a r b o n a t e w i t h i n t h e 51 t o 87 p e r c e n t i l e . T h i s
i s indeed unusual s i n c e l e v e l s of c h l o r i d e , sulf a t e and b i c a r b o n a t e i n r e c h a r g e areas i n western
and c e n t r a l Nevada g e n e r a l l y were found t o be
below 3, 21 and 245 mg/l, r e s p e c t i v e l y (Bohm,
Abstract
Electrical c o n d u c t i v i t i e s of s p r i n g waters i n
t h e S t i l l w a t e r Range, t h e Augusta, Clan Alpine and
Desatoya Mountains, i n d i c a t i n g varying l e v e l s o f
i o n i c c o n c e n t r a t i o n , w e r e compiled. Anomalously
h i g h i o n i c c o n c e n t r a t i o n s are l a r g e l y l i m i t e d t o
t h e n o r t h e r n S t i l l w a t e r Range. High l e v e l s of
s u l f a t e , c h l o r i d e , and b i c a r b o n a t e may t o a
c e r t a i n e x t e n t be d e r i v e d from m i n e r a l i z e d and
s c a p o l i t i z e d zones and l i m e s t o n e s i n Mesozoic
s e d i m e n t a r y and igneous rocks. However, t h e
h i g h e s t b i c a r b o n a t e l e v e l s are found i n s p r i n g s
emerging from igneous r o c k s . Their close
p r o x i m i t y to a major f a u l t and t h e o c c u r r e n c e o f
h i g h C02 p r e s s u r e s i n t h e Dixie V a l l e y geothermal
system may s u g g e s t a geothermal s o u r c e of Cop
b e n e a t h t h e S t i l l w a t e r Range.
1982).
E l e c t r i c a l c o n d u c t i v i t i e s measured i n groundwaters i n mountain r e g i o n s were g a t h e r e d by t h e
Bureau o f Land Management i n 1982 (B. S u l a r i a and
D. Schafersman, p e r s o n a l communication, March
1984).
These d a t a were augmented with d a t a coll e c t e d by t h e a u t h o r d u r i n g f i e l d work i n 1983/84.
The d a t a were normalized to a temperature of 25OC
and p l o t t e d on a map i n F i g u r e 1, c o v e r i n g t h e
n o r t h e r n S t i l l w a t e r Range, t h e Augusta, Clan
Alpine and Desatoya Mountains.
The n o r t h e r n
S t i l l w a t e r Range and a small s e c t i o n i n t h e Clan
Introduction
Geothermal e x p l o r a t i o n i n t h e Dixie V a l l e y
geothermal system i n i t i a t e d i n the l a t e 1970's has
s t i m u l a t e d i n t e r e s t i n t h e h y d r o l o g i c system of
t h e D i x i e V a l l e y r e g i o n . A l a r g e amount of hydrochemical d a t a from h o t s p r i n g s , w e l l s and mountain
s p r i n g s and c r e e k s have been g a t h e r e d (Bohm e t
a l . , 1 9 8 0 ) . Anomalously h i g h c o n c e n t r a t i o n s of
i o n s i n mountain s p r i n g s i n t h e S t i l l w a t e r .Range
l e d to t h e s p e c u l a t i o n t h a t geothermal a c t i v i t y
o c c u r s i n some parts of t h e S t i l l w a t e r Range.
However, t h e evidence a v a i l a b l e a t t h a t t i m e
remained i n c o n c l u s i v e . S i n c e t h e n t h e a u t h o r h a s
collected more f i e l d d a t a i n o r d e r t o s u b s t a n t i a t e
t h e presumptions made earlier. I t is t h e purpose
o f t h i s paper t o preview ongoing r e s e a r c h and
compare t h e area w i t h r e g i o n a l t r e n d s o f mountain
s p r i n g chemisty around n o r t h e r n Dixie Valley.
Discussion
The chemical composition of t h e groundwaters
i n t h e n o r t h e r n S t i l l w a t e r Range is unusual i n
t h a t t h e i o n i o c o n c e n t r a t i o n s are much h i g h e r t h a n
what would be expected i n a h i g h mountain r e c h a r g e
area. c h l o r i d e ranges between 28 and 605 mg/l,
s u l f a t e r a n g e s between 20 and 725 mg/l and bicarbonate a l k a l i n i t y r a n g e s between 134 and 436 mg/l.
These c o n c e n t r a t i o n r a n g e s were compared w i t h
cumulative frequency d i s t r i b u t i o n s of groundwaters
from the S i e r r a Nevada and western and c e n t r a l
Nevada ( l i t e r a t u r e d a t a g a t h e r e d by Bohm, 1982).
w i t h i n t h e s e frequency d i s t r i b u t i o n s t h e c h l o r i d e
0
FIGURE 1
ELECTRICAL CONDUCTIVITIES OF SPRING WATERS I N THE
STILLWATER RANGE AND THE CLAN ALPINE AND DESATOYA
MOUNTAINS. GEOLOGY AFTER SPEED ( 1 9 7 6 ) .
369
BOHM
The molar r a t i o s of HCOj/Cl of s p r i n g waters
from t h e S t i l l w a t e r Range were p l o t t e d on a map i n
F i g u r e 2 . R a t i o s of 1.4 and g r e a t e r o c c u r o n l y i n
s p r i n g waters i n t h e v i c i n i t y of t h e White Rock
Canyon F a u l t . These s p r i n g s have t h e h i g h e s t
bicarbonate a l k a l i n i t i e s i n the northern
S t i l l w a t e r Range (more than 400 mg/l a t 7000 f e e t
around White Rock Canyon). This is somewhat
unusual s i n c e they are a l l l o c a t e d i n igneous
rocks of t h e J u r a s s i c Humboldt L o p o l i t h and
T e r t i a r y r h y o l i t e s . D e r i v a t i o n of a l k a l i n i t y from
d i s s o l u t i o n of limestones i n surrounding format i o n s seems u n l i k e l y , s i n c e t h e r a t i o s of
(Ca+Mg)/HC03 are too low. A d d i t i o n a l l y , bicarbonate a l k a l i n i t i e s d e r i v e d from b i o g e n i c C 0 2 i n t h e
s o i l zone of an a r i d environment are n o t expected
to be t h a t high.
Alpine Mountains c l e a r l y s t a n d o u t a s areas of
h i g h l y c o n c e n t r a t e d groundwaters, i .e., e l e c t r i c a l
These
c o n d u c t i v i t i e s g r e a t e r than 1000 micromhos
waters seem t o occur i n c l o s e proximity t o outc r o p s of t h e Humboldt Lopolith.
However, t h e y
also occur i n areas u n d e r l a i n by T r i a s s i c and
J u r a s s i c pelites. I n some i n s t a n c e s t h e s e a r g i l l i t e s c o n t a i n i n t e r c a l a t e d limestones and
dolomites.
.
The high anion l e v e l s can be explained i n
s e v e r a l ways. Stable i s o t o p e d a t a i n d i c a t e some
e v a p o r a t i o n i n t h e mountain c r e e k s (Ingraham,
1982). Evaporation from shallow ground water
tables i n t h e v i c i n i t y of s p r i n g o r i f i c e s i s unl i k e l y t o happen, s i n c e t h e l e v e l s of p H and temp e r a t u r e (below 7.9 and 10°C, r e s p e c t i v e l y ) i n t h e
mountain s p r i n g s appear t o be too low t o i n d i c a t e
evaporation. Even i f some evaporation may occur,
i t could n o t e x p l a i n why it would raise i o n conc e n t r a t i o n s i n o n l y one l i m i t e d area i n such a
p e r s i s t e n t and d r a s t i c manner. I n s t e a d , scapoli t i z e d zones (Speed, 1976) i n t h e Humboldt gabbroic complex could provide h i g h l e v e l s of chlori d e , and weathering r e a c t i o n s may be enhanced sign i f i c a n t l y by a c i d i t y provided by t h e o x i d a t i o n of
s u l f i d e s i n mineralized zones. Anomalous concent r a t i o n s of b i c a r b o n a t e a l k a l i n i t y could be
d e r i v e d from d i s s o l u t i o n of i n t e r c a l a t e d l i m e s t o n e s , p a r t i c u l a r l y i n t h e very n o r t h e r n end of
t h e n o r t h e r n S t i l l w a t e r Range.
The White Rock Canyon F a u l t (Whitney, 1980)
is b e l i e v e d t o provide a barrier f o r f l u i d flow
w i t h i n t h e Dixie Valley geothermal system ( B e l l e t
al., 1980)
I t could e x p l a i n why D i x i e H o t
S p r i n g s , l o c a t e d west of t h e f a u l t , produces sulf a t e - c h l o r i d e waters, whereas Sou Hot S p r i n g s ,
McCoy H o t Springs and Hyder Hot S p r i n g s located
east of t h e f a u l t produce b i c a r b o n a t e waters. The
geothermal w e l l DF6621, located east of t h e f a u l t
and completed i n igneous rocks of t h e H G b o l d t
L o p o l i t h , w a s a s t r o n g C 0 2 and HCO3 producer ( u p
t o 1100 mg/l HCO3), whereas DF4514, completed i n
metasediments w e s t of t h e f a u l t produced v e r y
l i t t l e C 0 2 and HCO3. This i n d i c a t e s t h a t t h e
e a s t e r n part of t h e geothermal r e s e r v o i r ( s 1 is i n
many i n s t a n c e s r i c h i n Cop. Even DF5218, comp l e t e d east of t h e f a u l t , produced around 400 ppm
HCO3 (Mariner e t al., 1983)
.
.
One e x p l a n a t i o n could be t h a t f r a c t u r e zones
associated w i t h t h e White Rock Canyon F a u l t s e r v e
a s c o n d u i t s f o r geothermal waters to emerge from
d e p t h . A similar mechanism has been proposed by
Barnes e t a l . (1981) f o r carbon d i o x i d e r i c h soda
s p r i n g s i n t h e S i e r r a Nevada. However, t h e l e v e l s
of s i l i c a never exceed 25 mg/l and t h e temperat u r e s do n o t appear t o i n d i c a t e geothermal waters.
Rather, it i s suggested t h a t C 0 2 emerges from t h e
geothermal r e s e r v o i r a t depth and is d i s s o l v e d i n
shallow ground waters i n t h e mountain r a n g e s . A t
s l i g h t l y a l k a l i n e pH l e v e l s t h e C 0 2 i s i n p a r t
converted to b i c a r b o n a t e . This would r e a d i l y
e x p l a i n t h e h i g h carbon d i o x i d e r e s s u r e s computed
f o r t h e s e s p r i n g s (more than lo-' a t m o s p h e r e s ) .
T h e r e f o r e t h e a p p a r e n t a s s o c i a t i o n of h i g h bicarbonate a l k a l i n i t i e s i n s p r i n g waters w i t h a d e e p
r e a c h i n g f a u l t s t r u c t u r e may s u g g e s t geothermal
a c t i v i t y below t h e n o r t h e r n S t i l l w a t e r Range.
The s o u r c e of COP a t d e p t h could be metamorp h i c r e a c t i o n s i n sediments, e.g. t h e l i m e s t o n e s
of t h e Boyer Ranch Formation. The Boyer Ranch
Formation is i n p a r t o v e r l a i n by and i n part i n t e g r a t e d i n t o t h e Humboldt L o p o l i t h (Speed, 1976).
The Humboldt L o p o l i t h is b e l i e v e d to a c t p a r t i a l l y
as a r e s e r v o i r rock f o r t h e Dixie V a l l e y geotherm a l system ( B e l l e t al., 1982). I t is l i k e l y t h a t
e f f e c t s s i m i l a r t o t h o s e suggested f o r t h e White
Rock Canyon F a u l t occur to a much lesser e x t e n t
throughout t h e n o r t h e r n S t i l l w a t e r Range.
FIGURE 2
MOLAR RATIOS OF HCO3/Cl I N SPRINGS AND GEOTHERMAL
WATERS I N DIXIE VALLEY AND THE STILLWATER RANGE
GEOLOGY AFTER WILLDEN AND SPEED (197 41, JOHNSON
(1977) AND SPEED (1976).
370
Bohm, B., 1982, C o n t r o l s on Ground Water Chemistry
i n C e n t r a l and Western Nevada, D i s s e r t a t i o n ,
U n i v e r s i t y of Nevada, Reno, Nevada.
Summary and Conclusions
I n summary, it can be s a i d t h a t t h e s p r i n g
water c h e m i s t r y i n t h e n o r t h e r n S t i l l w a t e r Range
s t a n d s o u t as a n anomalous f e a t u r e r e l a t i v e t o
o t h e r groundwater c h e m i s t r i e s i n h i g h mountain
ranges around t h e Dixie V a l l e y geothermal s y s tem
The anomaly can n o t be e x p l a i n e d f u l l y a t t h i s
s t a g e . I t a p p e a r s t h a t i n some i n s t a n c e s p a r t i c u lar rock t y p e s may c o n t r i b u t e h i g h l e v e l s of sulf a t e and c h l o r i d e . A d d i t i o n a l l y , e v a p o r a t i o n may
raise i o n i c c o n c e n t r a t i o n s i n c r e e k waters. Howe v e r , t h e h i g h l e v e l s of b i c a r b o n a t e a l k a l i n i t y
are d i f f i c u l t t o e x p l a i n w i t h t h e s e p r o c e s s e s . I t
a p p e a r s as though some of t h e h i g h b i c a r b o n a t e i n
t h e s p r i n g waters is a s s o c i a t e d w i t h a major f a u l t
s t r u c t u r e i n t h e D i x i e v a l l e y geothermal system.
I t is t h u s concluded t h a t t h e anomalous s p r i n g
water c h e m i s t r y i n t h e n o r t h e r n S t i l l w a t e r Range
may i n d i c a t e geothermal a c t i v i t y a t depth.
Bohm, B., R.L. Jacobson, M.E.Campana and N.L.
Ingraham, 1980, Hydrology and Geochemistry,
I n Geothermal R e s e r v o i r Assessment Case
Study, Northern Basin and Range Province,
Northern D i x i e Valley, Nevada, Vol.1, Mackay
Min. R e s . I n s t . , Univ. Nevada, Reno, p. 159.
.
Ingraham, R.L. Jacobson and
Campana, 1980, Environmental I s o t o p e
Hydrology of t h e D i x i e V a l l e y Geothermal
System, I n Geothermal R e s e r v o i r Assessment
Case Study, Northern Basin and Range
Province, Northern D i x i e Valley, Nevada,
Vo1.3, Mackay f i n . R e s . I n s t . , Univ. Nevada,
Reno, ~ p p .C.
Bohm, B.,
Ingraham, N e i l L., 1982, Environmental I s o t o p e
Hydrology of t h e Dixie Valley Geothermal
System, Dixie Valley, Nevada, M.St T h e s i s ,
U n i v e r s i t y of Nevada, Reno, Nevada, 1982.
The same e f f e c t s are p r o b a b l y masked i n t h e
Dixie V a l l e y graben by l a r g e accumulations of c o l d
groundwater i n t h e a l l u v i a l d e p o s i t s . The h o t
s p r i n g s i n t h e v a l l e y a p p e a r t o be e x c e p t i o n s . I n
o t h e r words, c e r t a i n geothermal phenomena may i n
some cases be d e t e c t a b l e i n a mountain range. The
h y p o t h e s i s should be t e s t e d w i t h d e t a i l e d c o l l e c t i o n of environmental i s o t o p e d a t a . This unders t a n d i n g may e v e n t u a l l y l e a d t o new approaches i n
t a r g e t i n g geothermal e x p l o r a t i o n w e l l sites.
Johnson, M.G.,
1977, Geology and Mineral D e p o s i t s
of P e r s h i n g County, Nevada, Nev. Bur. Min.
and Geol., Bull. 8 9 .
Mariner, R.H.,
Presser, and W.C. Evans, 1983,
Geochemistry of Active Geothermal Systems i n
t h e Northern Basin and Range Province,
Geothermal Resources Council, S p e c i a l R e p o r t
No. 13, 1983, ,p. 95.
References
K i s t l e r , mar mariner and T.S.
Barnes, I., R.W.
P r e s s e r , 1981, Geochemical Evidence on t h e
Nature of t h e Basement Rocks of t h e S i e r r a
Nevada, C a l i f o r n i a , U.S. Geol. Survey Water
Supply Paper 2181.
Bell,
N.L.
M.E.
Speed, R.C.,
1976, Geologic Map of t h e Humboldt
L o p o l i t h and Surrounding Terrane, Nevada,
Geologic S o c i e t y of America, Map S e r i e s MC14.
Whitney, R.A.,
1980, S t r u c t u r a l - T e c t o n i c Analysis,
I n Geothermal R e s e r v o i r Assessment Case
Study, Northern Basin and Range Province,
Northern D i x i e Valley, Nevada, V o l . 1 , Mackay
Min. R e s . I n s t . , Univ. Nevada, Reno, p. 61.
E.J.,
D.B.Slemmons, R.A. Whitney, T.R. Bard,
R.L. Jacobson, M.E. Campana, R.W.
Juncal,
L.T.
Larson, B.W. Bohm-and N.L. Ingraham,
1980, Models of t h e D i x i e V a l l e y Geothermal
System, I n Geothermal R e s e r v o i r Assessment
Case Study, Northern Basin and Range
Province, Northern D i x i e Valley, Nevada,
V o l . 1 , Mackay Min. R e s . I n s t . , Univ. Nevada,
Reno, p. 206.
Willden, R. and R.C. Speed, 1974, Geology and
Mineral Deposits of C h u r c h i l l County, Nevada,
Nev. Bur. Min. and Geol., B u l l . 83.
371