University of Nevada

Reno

/SILICATE AND CARBONATE SEDIMENT-WATER RELATIONSHIPS IN

WALKER LAKE, NEVADA

A Thesis Submitted in Partial Fulfillment of the

Requirements for the Degree of

Master of Science in Geochemistry

by

Ronald J. Spencer MINES 2 - UBKAKY %?:

The thesis of Ronald James Spencer is approved:

University of Nevada

Reno

May 1977 ACKNOWLEDGMENTS

The author gratefully acknowledges the contributions of Dr.

L. V. Benson, who directed the thesis, and Drs. L. C. Hsu and R. D.

Burkhart, who served on the thesis ccmnittee. A special note of thanks is given to Pat Harris of the Desert Research Institute, who supervised the wet chemical analyses on the lake water and pore fluids. I also would like to thank John Sims and Mike Rymer of the

U. S. Geological Survey, Menlo Park, for their effort in obtaining the piston core; and Blair Jones of the U. S. Geological Survey,

Reston, for the use of equipment and many very helpful suggestions.

Much of the work herein was done as a part of the study of the

"Dynamic Ecological Relationships in Walker Lake, Nevada", and was supported by the Office of Water Research and Technology through grant number C-6158 to the Desert Research Institute. I thank the other members involved in the study; Drs. Dave Koch and Roger

Jacobson, and Joe Mahoney, Jim Cooper, and Jim Hainiine; for advice in their fields of expertise and help in sample collection.

Special thanks are extended to my wife, Laurie, without whose help and support this thesis could not have been completed. A final note of thanks to Tina Nesler, who advised Laurie in the typing of the manuscript. ABSTRACT

Walker lake is a closed basin lake located in west-central

Nevada. The lake solutes were acquired through dissolution of evap- orite minerals deposited by a preexisting lake, and weathering of materials within the basin transported by the Walker River. Evapora­ tive concentration, biologic activity, and mineral precipitation have altered the composition of the lake. This has reuslted in a Na-Cl-

HCO^-SO^ water, with a TDS of ^ 10,500 mg/1.

Calcium is removed from solution through the formation of car­ bonate minerals; calcites and monohydrocalcite are present in the sediment. Magnesium is removed from solution through incorporation in calcites and clay minerals, primarily detrital mixed-layer smectites and illites. Minor removal of sodium and potassium by the clay min­ erals also occurs within the lake and sediment. The biotic ccnmunity removes silica (diatcm frustules) and sulfate (anaerobic reduction) from solution, and adds carbon (photosynthesis, respiration, and organic decay) to the system. XV

TABLE OF CONTENTS

SIGNATURE P A G E ...... i

ACKNOWLEDGMENTS ...... ii

ABSTRACT ...... iii

LIST OF FIGURES ...... vi

LIST OF TABLES...... ix

INTRODUCTION ...... 1

SAMPLE COLLECTION AND ANALYSIS ...... 4

Sample Collection ...... 4 In Situ Measurements ...... 5 Pore Fluid Extraction ...... 5 Wet Chemical Analyses ...... 6 Sediment Preparation ...... 6 X-ray Diffraction ...... 7 Clay Chemistry ...... 8 WATEQF ...... 9

RESULTS ...... 10

Walker Lake Chemistry ...... 10 Carbonate Formation From Present Lake Water ...... 10 Silicate Deposition From Present Lake ...... 13 General Description of Cores ...... 13 Pore Fluids ...... 16 Carbonate Miner al o g y ...... 33 Silicate Mineralogy ...... 46 Clay Chemistry ...... 46 Salt Budgets ...... 48

INTERPRETATION AND DISCUSSION ...... 57

Aqueous P h a s e ...... 57 Solid Phases...... 58 Carbonate System...... 67 Silicate System ...... 71 Salt Budgets ...... 75 V

CONTENTS (Continued)

SUMMARY AND CONCLUSIONS ...... 78

Sediment-Water Reactions ...... 30

REFERENCES CITED ...... 83

APPENDIX 87 LIST OF FIGURES

Figure 1. Sample Locations ...... 11

Figure 2. Sample Depths; Core Lengths ...... 18

Figure 3. Sodium With D^pth in the Pore Fluids, Cores B - F ...... 19

Figure 4. Sodium With Depth in the Pore Fluids, Core G ...... 20

Figure 5. Potassium With Depth in the Pore Fluids, Cores B - F ...... 21

Figure 6. Potassium With Depth in the Pore Fluids, Core G ...... 22

Figure 7. Chloride With Depth in the Pore Fluids, Cores B - F ...... 23

Figure 8. Chloride With Depth in the Pore Fluids, Core G ...... 24

Figure 9. Sulfate With Depth in the Pore Fluids, Cores B - F ...... 25

Figure 10. Sulfate With Depth in the Pore Fluids, Core G ...... 26

Figure 11. Carbon With Depth in the Pore Fluids, Cores B-F ...... 27

Figure 12. Carbon With Depth in the Pore Fluids, Core G ...... 28

Figure 13. Calcium With Depth in the Pore Fluids, Cores B-F...... 29

Figure 14. Calcium With Depth in the Pore Fluids, Core G ...... 30

Figure 15. Magnesium With Depth in the Pore Fluids, Cores B - F ...... 31 vii

FIGURES (Continued)

Figure 16. Magnesium With Depth in the Pore Fluids, Core G ...... 32

Figure 17. Silica With Depth in the Pore Fluids, Cores B - F ...... 34

Figure 18. Silica With Depth in the Pore Fluids, Core G ...... 35

Figure 19. PH With Depth in the Pore Fluids, Cores B - E ...... 36

Figure 20. PH With Depth in the Pore Fluids, Core G ...... 37

Figure 21. Aluminum With Depth in the Pore Fluids, Cores B - E ...... 38

Figure 22. Iron With Depth in the Pore Fluids, Cores B - E ...... 39

Figure 23. Phosphate With Depth in the Pore Fluids, Cores B - E ...... 40

Figure 24. Percent Carbonate Minerals, Cores B - E ...... 41

Figure 25. Percent Carbonate Minerals, Core G ...... 42

Figure 26. X-ray Diffraction Patterns ...... 43

Figure 27. Ion Activity Product (CaCO^) Cores C, D, and G ...... 45

Figure 28. Cation Exchange Capacity (CSC) Core G ...... 49

Figure 29. Exchangeable Sodium and Calcium, Core G ...... 50

Figure 30. Exchangeable Potassium and Magnesium, Core G ...... 51

Figure 31. Subareas Used in Salt Budget Calculations ...... 54 viii

FIGURES (Continued)

Figure 32. Monohydrocalcite Precipitate and C r u s t ...... 59

Figure 33. Calcium Carbonate ...... 61

Figure 34. Detrital Sediment and Diatcm F r u s t u l e s ...... 62

Figure 35. Activity-Activity Diagram Mg-Silicates ...... 72 LIST OF TABLES

Table 1. Lake Chemistry ...... 12

Table 2. Saturation D a t a ...... 14

Table 3. Sediment Mineralogy ...... 15

Table 4. Radiocarbon Age Determinations ...... 17

Table 5. Clay Chemistry ...... 47

Table 6. Masses of Na, K, Ca, Mg, U, Cl; River and La k e ...... 52

Table 7. Masses of Na, K, Ca, Mg, U, Cl; Pore Fluids ...... 55

Table 8. Masses of Ca, Mg, Na, K; S e d i m e n t ...... 56

Table 9. Ratios of Mg, Fe, Al, Si, and Exchangeable Cations in C l a y s ...... 64

Table 10. Structural Clay Formulas ...... 65

Table 11. Salt Budgets ...... 76

Table 12. Sediment-Water Reactions ...... 81

APPENDIX

Table 1. WATEQF Thermochemical Data ...... 88

Table 2. WATEQF Species Constants ...... 92

Table 3. Changes to WATEQF ...... 94

Table 4. Walker Lake Chemical Analyses ...... 97 INTRODUCTION

Walker Lake is located in Mineral County, Nevada, and occupies a portion of the Lahontan Basin. At the present, the lake is ap­ proximately 21 by 8 km in maximum length and width, with the long- est dimension oriented north-south. The lake is approximately 33 m , 12 maximum depth, with a total volume of 3.5 x 10 1.

The lake is bounded on the east by the Gillis Range, and on the west by the Wassuk Range. The Walker River enters at the north end.

The drainage of the river extends to the Sierra Nevada and covers an area of about 13,700 square km.

There are a wide variety of rock types in the basin. The upper portion of the basin consists largely of quartz diorites, quartz monzonites, and the granitic rocks of the Sierra Nevada. Between the Sierra Nevada and Walker Lake, the basin rock types include

Mesozoic metavolcanics and metasediments, Caretaceous granites, quartz monzonite, and granodiorite, Tertiary volcanics and sediments, as well as Tertiary to Recent alluvium (Erwin, 1970). In the area of the lake, the Gillis Range is comprised of intermediate to felsic volcanic rocks with seme granitic rocks present; the Wassuk Range also contains both volcanic and granitic rocks (Ross, 1951).

Numerous studies of other saline lakes have been performed.

These include studies by Eugster (1970) on Lake Magadi, Hardie

(1968) on Saline Valley, and work by Jones (1965) on Deep Springs

Lake. Other studies include those of Jones et al (1977) on Lake 2

Magadi, Phillips and Van Denburgh (1971) on Abert, Summer, and

Goose Lakes, and Van Denburgh (1975) on Abert and Summer Lakes.

Models for the evolution of closed basin lakes have been presented by Jones (1966) and by Hardie and Eugster (1970).

Jones (1966) presented a model for the "Geochemical Evolution of Closed Basin Water in the Western Great Basin." The geochemical evolution of closed basin waters is described as a function of sol­ ution, transport, mineral precipitation, and evaporative concentra­ tion. The factors controlling the chemical composition of closed basin water are divided into primary, solute acquisition, and secon­ dary, modification, influences.

Primary influences are a function of the lithologies of the material with which the water in the basin cones in contact. If evaporite deposits are present, these will exert a dominant influ­ ence on the composition of the waters in the basin. A second pri­ mary influence is silicate hydrolysis, which may be expressed gen­ erally as follows:

primary silicate + H^O + CC^ = clay + cation

+ k c o 3~ + n4sio4

Feth et al (1964) and Garrels and Mackenzie (1967) used a similar model in explaining the chemical composition of springs in the

Sierra Nevada. An overriding control on the primary influences are the basic hydrologic characteristics of the basin, such as precipi­ tation, infiltration, circulation, and runoff. These factors control 3

the extent of weathering and transport of material within the basin.

Secondary factors influencing the composition of closed basin waters include evaporative concentration, organic reactions, and mineral precipitation. The organic reactions include the addition of C0? to the system, such as photosynthesis, and the resulting res­ piration and decay. The anaerobic decay of organic material may also give rise to bacterial sulfate reduction and the formation of sulfide. Dissolved silica is also directly influenced by biologic activity. The precipitation of less soluble mineral species, such as calcium carbonate, calcium sulfate, or sepiolite, is also a secondary control on the composition of closed basin waters.

This study is concerned with the interpretation of geochemical influences on the composition of lake water, pore fluids, and sed­ iment at Walker Lake. A geochemical model for the interactions of the lake water, pore fluids, and sediment is presented; a general model of the evolution of the lake is also presented. These models are based on the water chemistry, the sediment mineralogy, and salt budget calculations. The lake water and pore fluid chemistry in combination with the mineralogy, as determined by x-ray diffrac­ tion (XRD), are used to define the carbonate system. In the sili­ cate system, the XPD data is supplemented by chemical analyses to better define the clay mineral composition. The lake water, pore fluid, and sediment compositions are used to determine salt budgets, and to define reactions between solid phases and solution. The sediment-water relationships are also examined with respect to available thermochemical data. SAMPLE COLLECTION AND ANALYSIS

Materials used in this study include six gravity cores, one piston core, and several sediment dredge samples from Walker Lake.

Water samples were also collected frcm the lake at two month inter­ vals during 1975-1977. Additionally, water and suspended sediment from the Walker River were also collected. Several grab samples of a carbonate crust were also taken from rocks along the shore of the lake.

SAMPLE COLLECTION

Water samples for wet chemical analyses were collected from the lake using Van Dooren bottles. A portion of the sample was then transferred to a one gallon cubitainer; a second portion was trans­ ferred to a one quart plastic bottle, which was chilled. A 125 ml split was filtered through a 0.45 u millipore membrane into a plastic bottle, and a second 125 ml split was filtered through a 0.1 p mil­ lipore membrane into a 125 ml glass bottle, and was acidified.

Seven sediment cores were collected at the lake. Six of these were collected using a gravity corer, with a plastic liner. The liners were cut and capped at the lake and placed on ice until pro­ cessing. The seventh core was a piston core collected in coopera­ tion with the United States Geologic Survey (U. S. G. S.). Sediment dredge samples were collected using an Eckman dredge. 5

IN SITU MEASUREMENTS

Temperature, pH, specific conductance, and dissolved oxygen were measured in the field, using a Hydrolab surveyor model 6D on lake water samples. Additionally, pH was measured using Orion specific ion meters (401 A) and combination electrodes (91-02) on both water and dredge samples. Eh was also measured on the dredge samples, using an Orion meter (401 A) and platinum redox electrode

(96-78). Alkalinity titrations were also performed on several occasions in the field, and found to be in good agreement with laboratory values.

PORE FLUID EXTRACTION

In the laboratory, 10 cm sections of the cores were squeezed, using a modified version of the apparatus described by Kalil and

Goldhaber (1973). This process allowed pore fluids to be removed without contact with the air. During squeezing, the core section was cooled by circulating ice water through copper coils around the section. The first 5 ml of fluid extracted from the sample was discarded. Immediately after extraction, pH and Eh were measured on a portion of the sample. The remainder was filtered through a

0.1 p millipore menbrane into two vials. One split was untreated;

Cl, S04, C (alkalinity), and Si09 were measured on this. The second was acidified and used to analyze for Na, K, Ca, Mg, Al, Fe, and Mn.

On more concentrated samples, a 1:10 dilution was done immediately after extraction. Sulfide determinations were also made on portions of two cores; a Beckman specific ion electrode (39610) was used. 6

Standards and samples were analyzed in a 25 percent SAOB solution.

WET CHEMICAL ANALYSES

In general, cation analyses of water samples were done on fil­

tered acidified samples by atomic absorption. Appropriate dilutions

on concentrated samples were made using a Hamilton digital dilutor,

such that the analysis fell within the dynamic range for the species

being determined (Varian Techtron, Analytical Methods for Flame

Spectroscopy).

Chloride was determined through a titration with silver nitrate,

using a potentiometric end point (Standard Methods, 13th, 1971, p

377.). Alkalinity was determined through a titration with hydro­

chloric acid, using a potentiometric end point, and the result was

reported as bicarbonate (Standard Methods, 13th, 1971, p 52.).

Sulfate was determined using the thorin method (Brown et al, 1970).

Reactive silica was determined colorimetrically, using molybdate

blue, on filtered samples (Standard Methods, 13th, 1971, p 303.).

SEDIMENT PREPARATION

As the cores were sectioned for processing in the laboratory,

samples were taken and weighed every 10 cm. These samples were then

dried in a dessicator, and the weight percent water determined.

Additional samples were also taken for mineralogical determinations.

An untreated sample was set aside for XRD analysis, and a second

sample was dispersed in a column of distilled water. The < 2 y

portion was then separated by gravity settling. Stokes Law was used

to determine settling rates (Carroll, 1970). This portion was used to determine clay chemistry by XRD. The > 2 y fraction was examined microscopically.

Further separations on the < 2 y fraction of some samples were also done. This work was performed by the author at the U. S. G. S. headquarters in Reston, Virginia, using the centrifuge equipment available there. Separations were made, and the materials examined, by XRD on the 1-2 y, 0.5-1 y, 0.2-0.5 y, 0.08-0.2 y, and < 0.08 y size fractions. The fractions < 0.2 y were found to be free frcm non-clay minerals. The material, therefore, was separated into the

< 0.2 y fractions for further analysis. The material was cleaned both through centrifugation and rinsing over a 0.1 y filter with distilled water.

X-RAY DIFFRACTION

Samples were analyzed using a Norelco model 12045 3/3 XRD unit.

Radiation used was Ni Cu filtered K a. Bulk sediment samples were dried and ground at room temperature. Unoriented mounts in aluminum sample holders were then scanned frcm 10-60 degrees 28. Estimates of major mineral species were made, using peak heights relative to those of prepared standard patterns. The peaks used were 101 of quartz, 104 of calcite, 040 of feldspar, and 111 and 112 of mono- hydrocalcite. Scans were also run at slower speeds between 28 and

32 degrees 20, in order to determine the Mg content in calcite. The calcite 104 peak position was determined, using halite as an internal standard. The data of Plummer and Mackenzie (1974) was used to determine mole percent iMgCCp. 8

Clay mineralogy was determined on oriented glass slide mounts scanned from 2-32 degrees 28. Estimates were made of the relative proportions of the clay minerals, using ratios of the areas of the basal reflections on glycolated mounts (Biscaye, 1965).

CLAY CHEMISTRY

Cation exchange capacity (CEC), exchangeable cations, and bulk clay chemistry were determined on the < 0.2 u fraction of sediment of several core sections. This size fraction was selected because it was found, by XRD, to be free of non-clay minerals.

A modified version of the techniques of Sawhney et al (1959) was employed for exchangeable cation determinations. A weighed clay sample (v 0.100 g) was placed in 25 ml of a 2 N SrCl2 solution. The clay was dispersed using a Varian Aerograph sonic cleaner. The solution was then removed from the clay by filtration. Exchangeable

Ca, Mg, Na, and K were then determined by atomic absorption. Three samples were run through this procedure a second time to establish the completeness of the exchange.

The clay was then rinsed with distilled water, in order to re­ move excess Sr, and then placed in 25 ml of a 2 N CaCl2 solution.

The clays were dispersed using the sonic cleaner, and the solution removed from the clays by filtration. Sr was then determined by atonic absorption, giving a measure of the CEC.

The bulk clay chemistry was also determined on the < 0.2 p size fraction of several samples. The methods of Shapiro (1975) were employed here. The samples were fused, using a lithium 9

metaborate-lithium tetraborate flux. The resulting beads were then dissolved. Wet chemical analyses were run to determine SiC^, Al,

Fe, Mg, Ca, Na, and K.

WATEQF

WATEQF is a FORTRAN TV computer program that models the ther­ modynamic speciation of inorganic ions and complex species for a given water analysis (Plummer et al, 1976; Truesdell and Jones,

1974). Individual ion activity coefficients are calculated using the extended form of the Debeye-Huckel equation.

A z.2 f L log y . ------+ b I 1 + B a /L

Where is the individual ion activity coefficient, A and B are constants depending on the solvent (water), I is the ionic strength, z the charge of the ion, a and b are parameters derived from curve fitting of mean salt activity coefficients for the various species.

A list of log K (equilibrium constants) used in the program is given in Appendix 1. 10

RESULTS

WALKER LAKE WATER CHEMISTRY

The analytical data available for lake water chemistry was

reduced by calculating an average of 35 analyses taken during a one year period. The analyses chosen were fran station 14 (Figure 1),

sampled at five depths, 1, 5, 10, 20, and 26 m, on seven dates during

1975 and 1976. The results of these calculations are shown in

Table 1, including the logarithms of activities of the major ions.

The major ions in the lake remained nearly constant over the one year period. The temperature ranged fran 6.0°Celsius (C)

throughout the lake during the winter, to 25.0°C near the surface during the summer.

Sodium is the major cation in the lake (Table 1) , accounting for

90 percent of the total cation equivalents. The lake is relatively

low in Ca, which accounts for < one percent of the total cation equivalents. The molar ratio of Na/Ca in the lake is nearly 500:1, and that of Mg/Ca 20:1.

The anion equivalents are distributed between C, SO^, and

HCO^-CO^ (Table 1). Chloride accounts for 42 percent of the total anion equivalents, SO^ for 28 percent, and HCO^-CO^ for 30 percent.

CARBONATE FORMATION FROM PRESENT LAKE WATER

Formation of Ca-carbonate has been observed occurring in two environments at Walker Lake. The first is as an encrustation on

SPECIES mg/1 standard epm molality log activity deviation

Ca2+ 11.0 0.9 0.55 2 .77xl0~4 -4.34

Mg-2+ 136. 12. 11.2 5.65xl0~3 -2.99

Na+ 3120. 107. 135.7 1.37xl0_1 -1.01 K+ 166. 15. 4.2 4.29xl0-3 -2.52

Cl" 2260. 50. 63.7 6.43xl0-2 -1.33 2- 00 • SO / 2060. o 42.8 -2.26 4 2.17xl0_2 h c o 3“ 2900.* 70. 47.5 4.80xl0-2 -1.66

7+

8 -2.70 OJ ( OJ

sio2 0.71 0.44 1.19xl0~5 -4.99

TO 3~ 1.6 0.2 0.05 1.17X10-3 -8.69 0.025 0.005 9.37xl0~7 -20.18

Fe3+ <0.01

Total -dissolved :solids (TDS) = 10,650.

pH = 9.45 - 0.05 T°C = 6.0 - 25.0

eon cations = 153.3

epm anions = 155.7

TABLE 1. Average lake water chemistry 1975-1975. Log activity cal­

culated at 10°C using WATEQF. *HCO_ given as total alka­

linity measured in the field. 13

rocks along the shore; the second is in the deeper water, forming a fine, white, stringy precipitate on the bottom sediments. In both instances, the carbonate forms as monohydrocalcite (CaCO^'H^O).

The water chemistry described above was used to calculate sat­ uration data for the carbonate minerals which may be significant in

Walker Lake. The results of these calculations are shown in Table 2. \'

SILICATE DEPOSITION FROM PRESENT LAKE

Silicate deposition from the present lake consists primarily of detritus. Silica is also being deposited authigenically in the form of diatom frustules. As shown in Table 1, dissolved SiC^, Al, and

Fe are all low in the lake.

Aside frcm Si02 in diatom frustules, Al, Fe, and Si02 are trans­ ported to the sediment as detrital material. Quartz and feldspars, along with clays (primarily smectites and illites), all make up a significant portion of the material reaching the deeper portions of the lake floor as detrital sediments.

GENERAL DESCRIPTION OF CORES

The six gravity cores obtained at Walker Lake varied frcm 77-205 cm; additionally, a 467 cm piston core was recovered from the lake.

The location of each core is shewn in Figure 1. The deep lake sedi­ ments consist largely of silt and clay size material, with seme sand size quartz and feldspar. The core materials contained between 36 and 90 percent water by weight (Table 3); the trend being a decrease of water with depth. The core sections were black in color when recovered, and contained free I^S throughout. Six of the seven cores 14

PHASE KDG LOG IAP LOG IAP /X,

ANHYDRITE -4.49 -6.61 -2.11

ARAGONITE -8.19 -7.04 1.14

CALCITE -8.37 -7.04 1.37

DOLOMITE -16.64 -12.72 3.98

GYPSUM -4.60 -6.61 -2.01

HALITE 1.55 -2.34 -3.88

MAGNESITE -4.66 -5.68 -1.02

MIRABILITE -1.85 -4.30 -2.45

MONOHYDROCALCITE -7.46 -7.04 0.41

NAHCOLITE -0.69 -2.67 -1.98

NATRON -1.92 -4.74 -2.81

THENARDITE -0.16 -4.28 -4.12

THERMONATRITE 0.23 -4.72 -4.95

TRCNA -0.10 -7.39 -7.29

TABLE 2. Saturation data for mineral phases in Walker Take water.

Log log IAP, log IAP/X j , were calculated at 10°C

using WATEQF. 15

CORE/ w t % w t % wt % w t % w t % MOLE % w t % w t %

DEPTH (m) SOLID QTZ FSPAR MHYCAL CALC M G IN c a c o 3 CLAY CALC

B 0.05 10.8 11 9 24 20.4 45 B 0.35 15.1 9 9 4 15 11 16.7 49 B 0.65 17.6 10 9 18 3 11 18.0 44 B 0.95 21.3 16 10 3 17 12 17.5 47 B 1.25 24.9 10 10 8 3 10 9.5 44

C 0.05 10.7 10 8 25 21.3 48 C 0.35 14.6 10 12 12 10.3 48 C 0.65 17.5 10 13 12 7 11 16.5 46 C 0.95 22.0 10 10 10 4 12 11.7 50

D 0.05 12.8 10 7 26 22.0 40 D 0.35 14.9 12 12 21 17.8 42 D 0.65 17.0 11 12 7 9 10 50 D 0.95 20.7 10 11 19 10 50

E 0.05 12.6 7 7 22 18.7 48 E 0.15 14.8 6 6 24 20.4 45 E 0.55 13.4 11 10 10 8.5 52 E 0.95 17.0 8 10 14 11.9 50 E 1.35 20.8 10 15 5 3 11 7.3 47 E 1.55 26.8 11 11 15 10 13.5 50 E 1.65 28.7 8 10 16 10 14.5 50

G 0.05 12.0 10 8 24 20.4 45 G 0.45 18.6 12 13 18 3 11 17.9 39 G 0.95 20.2 12 15 7 12 12 16.3 41 G 1.45 21.7 9 8 20 12 17.5 50 G 1.95 20.3 7 7 30 7 28.1 45 G 2.45 24.6 26 19 28 5 26.6 20 G 2.95 64.0 27 32 13 <3 13.0 20 G 3.45 55.0 20 15 24 <3 24.0 34 G 3.95 50.0 23 10 22 <3 22.0 40 G 4.60 32.2 10 10 23 <3 23.0 48

TABLE 3. Sediment mineralogy; weight percent of minerals in

the solid fraction. 16

contained portions of a volcanic ash layer.

The volcanic ash encountered in the cores consists of five or six thin (1-2 irm) ash layers interbedded with lake sediments (1-

5 mm) . The ash layers allcw correlation, stratigraphically, be­ tween cores, and give a good reference plane to estimate sedimenta­ tion rates. Radiocarbon dates (Table 4) on several core sections extrapolated to the ash indicate that it was deposited approximately

1,200 yrs B. P. Figure 2 shews the location of the ash layer in each of the cores. This data yields a sedimentation rate of roughly 1-

1.5 mm/yr.

PORE FLUIDS

The points in the following figures are plotted at the mid point of each section; depths in cores are from sediment-water inter­ face. The results of the Na, K, Cl, SO^, and C analyses on the pore fluids are given in Figures 3-12. The concentration profiles with depth are similar for these species. The Na, K, Cl, SO^, and C concentrations in core B and the upper portion of core E decrease with depth. Concentrations of Na, K, Cl, S04, and C increase with depth in the remaining cores.

The concentration profiles for Ca with depth are shown in

Figures 13 and 14. In each core there is an initial increase of Ca in solution with depth. This is followed by a decrease with depth, except in core B. The concentration of Mg in the pore fluids (Fig­ ures 15 and 16) decrease with depth in all of the cores.

The results of the SiC^ measurements are given in Figures 17 17

RESULTS OF DATING ON WALKER LAKE CORES

CORE DEPTH (m) AGE (yrs.)

B 0.0-0.1 m o d e m

B 0.5-0.7 450 - 50

B 1.2-1.4 1,020 - 60

D 0.3-0.5 645 ~ 55

D 0.8-1.0 985 - 55

E 0.0-0.1 m o d e m

E 0.2-0.7 305 - 50

E 0.7-0.9 315 - 55

E 1.1-1.3 595 - 55

E 1.5-1.7 840 - 55

TABLE 4. Radiocarbon age determinations from cores B,

D, and E Figure 2. Sample depths; core lengths.

00 iue . oimwt dph n h pr fluids, pore the in depth with Sodium 3. Figure

DEPTH IN METERS BELOW SEDIMENT - WATER INI ERFACE oe B-F cores W LE LK CRS 3-F CORES LAKE ALKER 19 iue . oimwih et i te oe fluids, pore the in depth ith w Sodium 4. Figure

DEPTH IN METERS BELOW SEDIMENT- WATER INTERFACE oe G core W LE LK CR 6 CORE LAKE ALKER 20 Figure

. oasu ih et i te oe fluids, pore the in depth with Potassium 5. DEPTH IN METERS BEl.OW SEDIMENT - WATER INTERFACE cores AK LK CRS 3-r CORES LAKE WALKS B-F 2 1 iue . tsimwih et i te oe fluids, pore the in depth ith w otassium P 6. Figure

DEPTH IN METERS BELOW SEDIMENT WATER INTERFACE 2 . 0 — core AKR AE OE G CORE LAKE WALKER G. GL K" MG/L 300 I r “I

400 500

300 2 2 iue . hoie t dph n h pr fluids, pore the in depth ith w Chloride 7. Figure

DEPTH IN METERS BELOW SEDIMENT-WATER INTERFACE oe B-F cores 2000 AKR AE OE B-F CORES LAKE WALKER Cl L / 6 M 0 0 0 4 0 0 0 6 8000 2 3 F igure

DEPTH IN METERS BELOW SEDIMENT WATER INTERFACE l5 - 5-l 3.5-1 2.0 - .3 0 2.5 — .H A o.oH . hoie ih et i te oe fluids, pore the in depth with Chloride 8. — oe G core AKR AE OE 3 CORE LAKE WALKER I 1 14 12 IS 3 1 GL t O'3) IO rtX C MG/L G E K A L • A ^0 ! 9 24 iue . uft wt dph n h pr fluids, pore the in depth with Sulfate 9. Figure

DEPTH IN METERS DEI OW SEDIMENT - WATER INTERFACE oe B-F cores AKR AE OE 3-F CORES LAKE WALKER 2 5 Figure 10. Sulfate with depth in the pore fluids, fluids, pore the in depth with Sulfate 10. Figure

DEPTH IN METERS BELOW SEDIMENT WAI EH INTERFACE oe G. core AKR AE OE G CORE LAKE WALKER 2 6

F gr 12. igure

DEPTH IN METERS BELOW SEDIMENT - WATER INTERFACE abn ih et i te oe fluids, pore the in depth with Carbon oe G. core iue 3 Climwt dph n h pr fluids, pore the in depth with Calcium 13. Figure DEPTH IN MEIERS BELOW SEDIMENT - WATER INTERFACE 2.0 1.9 — 3 — — .3 1 1.7— . — 1.3 1.3 — 7.0- 1.6 — 1.4 — 1.2 — II. 9 — .9 . 3 — - € O co ■ • ■ 0 0 10 r cores AKR AE OE 3-F CORES LAKE WALKER B-F G /L Ca- MG / L 40 i o C A E K A L • I D F 3 E T 5 b 2 9 Figure 14. Calcium with depth in the pore fluids,

core G.

\ iue 5 Mgeimwt dph n h pr fluids, pore the in depth with Magnesium 15. Figure

DEP1H IN METERS BELOW SEDIMENT - WATER INTERFACE oe B-F cores AKR AE OE 3-f CORES LAKE WALKER 3 1 Figure 16. Magnesium with depth in the pore fluids fluids pore the in depth with Magnesium 16. Figure

DEPTH IN METERS DELOW SEDIMENT - WATER INTERFACE 5— .5 0 0.0 — G • E K A L . A oe G. core WALK R AE CORE G LAKE ER 33

and 18. In the upper portion of all of the cores there is an increase of SiCh in solution with depth. In cores B and E the SiO_ levels reach a maximum at about one m, 57 mg/1 in core E. Below this, SiC>2 decreases slightly. SiC^ increases with depth in cores

C, D, and F. In core G there is an increase in Si02, followed by a decrease and a second increase with depth.

The pH of the interstitial fluids extracted frcm the five cores are given in Figures 19 and 20. The pH of the lake, 9.45 - 0.05, is also shown. There is an initial decrease in the upper portion of core G, to 8.7 at 1.45 m; below this there is a general increase.

Cores C, D, and F shew this same trend. In the two more shallow cores, B and E, the pH decreases in the upper portions, and there is no consistent trend toward an increased pH with depth.

Aluminum and iron were determined on sections of cores B, C, D, and E; the results are given in Figures 21 and 22. Thera is a gen­ eral increase relative to the lake in the upper core sections. This is followed by a decrease with depth. Phosphate analyses fron cores

B, C, D, and E are plotted in Figure 23. In all cases there is a significant increase in PC>4 with depth in the cores.

CARBONATE MINERALOGY

The carbonate mineralogy, as determined by XRD on various core sections, is tabulated in Table 3. The percent carbonate minerals are graphically represented in Figures 24 and 25. The carbonates detected consist of mononydrocalcite, and calcite containing varying amounts of Mg; selected XRD patterns are shown in Figure 26. iue 7 Slc wt dph n h pr fluids, pore the in depth with Silica 17. Figure

DEPTH IN METERS BELOW SEDIMENT - WATER INTERFACE cores AKR AE OE B-F CORES LAKE WALKER B-F 3 4

iue 9 P ih et i te oe fluids, pore the in depth with PH 19. Figure

DEPTH IN METERS BELOW SEDIMENT-WATER INTERFACE oe B-E cores AKR AE CE B-F CC^ES LAKE WALKER 3 6 iue 0 P wt dph n h pr fluids, pore the in depth with PH 20. Figure Q Ul h- 2 3.0- ~ 2 IE UJ i U cc2.5— CD I U s > 2.0— w UJ o UJ 1.5- £ S 2 < £ UJ h- cc - 1.0- 1.0- - »- Ui c c

0- .0 4 DEPTH IN METERS BELOV/ SEDIMENT-WATER INTERFACE

3.5- FACE . - 0.0 p

. 85 90 9.5 9.0 5 8 8.0 u\ 1 LAKE A « 6 6 « oe G core AKR AE OE G CORE LAKE WALKER 0 pH 9 9 • Q 0 9 » A 9 37 Figure 21. Aluminum with depth in the pore fluids, fluids, pore the in depth with Aluminum 21. Figure

DEPTH IN METERS BELOW SEDIMENT—WATER INTERFACE . . 2.0 1 1.6 1.0 1.9 — 1.5 1.2- 1.7- 1.4 — 1.3- 1.1- . .8- .5 —i 9- .9 .6 7 .7“ : 8 2 J . — 1 y w c g w r a a t > ■ * v : * . »?. -

do a a Cl ® a 0.5 ku 5 «.:** oe B-E. E - B cores wu : AKR AE OE 9-F CORES LAKE WALKER s . 1.5 I.O a L Ai /L G M a . w;T»,a a yy* t-v1;. * w w w i v w - •••\> - w : v i w w * t-v1;.w yy* a a o LAKE A © 2.0 c 8 D E 2.5 iue 2 Io wt dph n h pr fluids, pore the in depth with Iron 22. Figure DEPTH IN METERS BELOW SEDIMENT-WATER INTERFACE oe B-E cores W LE LK CRS B-F CORES LAKE ALKER iue 3 Popae ih et i te oe fluids pore the in depth with Phosphate 23. Figure DEPTH IN METERS BELOW SEDIMENT-WATER INTERFACE oe B-E cores AKR AE OE B-F CORES LAKE WALKER L PC4J /L G M ' ■ iue 4 Pret abnt mnrl, oe B-E. E - B cores minerals, carbonate Percent 24. Figure

DEPTH IN METERS BELOW SEDIMENT-WATER INTERFACE 2 1.4- . .9- .3- 0 - a ©fl ao B 9 MHC = monohydrocalcite; all calcites con con calcites all monohydrocalcite; = MHC an rm 01 ml pret iMgC03> percent mole 10-12 from tain 0□ to © © WA , a 0 20 10 KR AE OE S-F CORES LAKE LKER ABNT MINERALS CARBONATE % © © • a□ ® □ S a © - o a o a □ C 9 © E 0 0 QOO H C MHC B Calcite act E Calcite D Calcile D MHC C Calcite B MHC H E MHC ■ 30 iue 25. Figure

DEPTH IN METERS BELOW SEDIMENT-WATER INTERFACE - .O O 2 4.0-| 0.5- 2.5- 3.0- 3.5- 1.5- 1 . . 0 0 - - I □ Monohydrocalcite Monohydrocalcite □ ecn croae ieas core minerals, carbonate Percent Clie C03 gC M % Calcite ® © □ - 12- r-, W LE LK CR G CORE LAKE ALKER 10 ABNT MINERALS CARBONATE %

<3« 12 20 » <3 □ © © Figure 26. X-ray diffraction patterns; 2-10 oriented glycolated; 16-35 no orientation. S=sinectite; I=illite; M=monohydrocalcite; P=feldspar; C=calcite; Q=quartz. 44

In general, monohydrocalcite is the predominant carbonate min­ eral in the upper metre oj. sediment. Magnesium containing calcites,

4—12 mole percent MgCO^, are most abundant in the next metre of sed­ iment. The lower portion of sediment from core G contains calcites which are low in I4g (< 3 mole percent MgCO^) .

The logarithms (log) of the ion activity products (IAP) for

CaCOs in the pore fluids from cores C, D, and G are shown in Figure

27. The plots also represent the IAP for monohydrocalcite (CaCCu-

H20) , since the activity of water is essentially one in the pore fluids. The logs of the equilibrium constants (K) for calcite, K , aragonite, Ka , and monohydrocalcite, 1^, are also plotted. Values were calculated at 10°C.

The > 37 ]i size fraction of several portions of core G were examined microscopically. Fragments of monohydrocalcite were ob­ served in the upper portion of the core. The birefringence of these fragments varied from first order to fourth order within a single grain. Portions of the grains gave uniaxial interference figures, and other portions biaxial, with a 2V frcm 5-15 degrees. The remains of the chitonous exoskeleton of Moina hutchinsonii, a zoo­ plankton found in the lake, were also observed. The chiton appeared to have been replaced by monohydrocalcite. Similar fragments and remains of Moina hutchinsonii were observed throughout the core, including portions of core where calcite was identified by XRD as the only carbonate mineral present. iue 27 Figure DEPTH IN METERS. BELOW SEDIMENT-V/ATER INTERFACE , , n G. and D, C, n o I AKR AE OE G CORE LAKE WALKER ciiy rdc (CaCC>3) , product activity cores 4 5 SILICATE MINERALOGY

The lake sediments contain quartz, feldspars, and clay minerals.

The results of the XRD analyses are given in Table 3, and selected

XRD patterns are given in Figure 26. Smectite is the dominant min­ eral found in the sediments. Some quartz, feldspar, illite, kaolin- ite, and chlorite were detected in all samples examined.

All of the sediment examined microscopically contained silice­ ous diatcm fragments. No attempt at estimating the total weight of the diatoms was made; this makes up a portion of the remaining solid material. Other organic material was also present throughout the cores. These may account for about 10 percent of the total solid mass. Feldspars were examined microscopically on several core sec­ tions . Generally, they shewed wide variation in composition within a single section. Both high and low temperature feldspars were also noted in most sections; all appeared to be detrital.

CLAY CHEMISTRY

The bulk chemistry, CEC, and exchangeable cations of the < 0.2 y size fraction of portions of core G were determined. The exchange­ able cations determined consisted of Ca, Mg, Na, and K. In the bulk clay determination, the cations mentioned above, along with Fe, Al, and SiO^, were analyzed. The results of the bulk clay measurements are given in Table 5. A standard clay (montmorillonite; Bums,

Mississippi 21) was analyzed along with the Walker Lake samples.

The composition of this clay, taken from the Preliminary Reports,

Reference Clay Minerals, American Petroleum Institute Research SAMPLE w t % w t % w t % w t % w t % w t % w t % DEPTH (m) N a 20 k 2o CaO MgO sio2 F e 2°3 M 2°3

DREDGE 1.0 1.3 0.8 8.1 6.6 7.2 33.1

G 0.4 2.0 1.9 0.8 6.2 8.3 10.5 58.4

G 1.0 0.8 1.7 1.9 4.3 9.1 12.2 53.5

G 1.5 0.9 1.8 2.1 3.9 8.4 12.0 60.9

G 2.0 1.3 2.1 1.6 4.0 9.6 12.3 52.2

G 3.0 1.6 2.7 1.3 7.0 9.2 10.6 48.9

G 4.0 1.8 2.1 1.2 5.1 8.6 11.0 49.2

G 4.5 0.6 1.8 1.8 4.9 8.2 11.0 52.3

Std 21 0.05 0.1 2.1 4.3 2.5 13.4 56.4

Std 21* 0.17 0.38 2.12 4.41 2.46 16.30 51.18

TABLE 5. Weight percent of oxide components in the < 0.2 p size fraction frcm core G, API

reference clay Std 21, data for Std 21* is frcm the Preliminary Reports, Reference

Clay Minerals, American Petroleum Institute Research Project 49. 49, is included as an indication of analytical error. The

CEC is shown diagramatically in Figure 28. The sun of the exchange­ able Ca, Mg, Na, and K is shown as one measure of CEC. The CEC, as measured by the exchange of Ca for Sr, is also given; the two mea­ sures agree well. Figure 29 shows the exchangeable Ca and Na for the clays. The exchangeable K and Mg are given in Figure 30.

SALT BUDGETS

Salt budgets were calculated for Na, K, Ca, Mg, Cl, and U.

Estimates of the time of the last dessication of the lake, the vol­ ume flux since that time, river concentrations over the period since dessication, and the present lake volume, were obtained frcm L. V.

Benson (personal communication). The last lake dessication was placed at 5,000 yrs B. P., and the volume flux since that time at 15 1.41 x 10 1. The average river concentrations were estimated as follows: Na 3.0 mg/1, K 0.84 mg/1, Ca 6.7 mg/1, Mg 1.48 mg/1, Cl

0.9 mg/1, and U 0.7 ug/1, based on analyses of river water in the upper portion of the basin during high and low flow in 1976. The- 12 present lake volume was estimated at 3.53 x 10 1; lake concentra­ tions were taken from the average lake values discussed previously;

U was determined by neutron activation by Lawrence Livermore Labora­ tory (1976) . The assumption was made that the entire volume flux was due to the Walker River. The mass flux from the river and the total mass in the lake for the species are given in Table 6.

In order to estimate the Ca, Mg, Na, K, Cl, and U in the sedi­ ment deposited over the past 5,000 yrs, the basin was divided into iue 8 Cto ecag cpct (E) cr G core (CEC), capacity exchange Cation 28. Figure

DEPTH IN METERS BELOW SEDIMENT-WATER INTERFACE o.o- 4.5- - .0 4 2 . - 0.5 2.5-1 3.0- 3.5- 1.5- - o . i . 0 - 70 AKR AE OE G CORE LAKE WALKER 90 E ME I G O /IO EQ M CEC O ^ O e O O O HO CEC O a O 9 0 o « T ] RIVER Q 9 x e O O

ons n io t a c • • O o & ® 0 130 4 9 iue 29.Figure

DEPTH IN METERS BELOW SEDIMENT-WATER INTERFACE O.O- 2 5-- - .5 4 . - 0.5 . - 4.0 2.5- 3.0- 3.5- 1.5- 1 . . 0 0 - - 0 O CA RIVER RIVER CA O ❖ NA RIVER RIVER NA ❖ A OE G CORE CA O A OE G CORE NA © O xhnebe oim n clim cr G. core calcium, and sodium Exchangeable AKR AE OE G CORE LAKE WALKUR 9 X CTOS MEQ/ICOG CATIONS EX. O O

30 9 9 CO 00 0 9 9 ® 0 00 60 I O o 9 O 5 0 iue 0 Ecagal ptsim n magnesium, and potassium Exchangeable 30. Figure

DEPTH IN METERS BELOW SEDIMENT-WATER INTERFACE o.o- 2 . - 0.5 0- .0 4 4.5- 2.5- 3.0- 3.5- 1.5- 1 . . 0 0 - - O O O O 0 oe G.• core OO 0 0 AKR AE OE G CORE LAKE WALKER 0 © X CTOS G/OOG O /IO EG M CATIONS EX. ❖ 10

9 ® 9 0 O 0 o 0 20 O MG RIVER RIVER MG O $ K OE G CORE K G© CORE MG O K RIVER RIVER K 5 1 DETRITAL CLAY

TOTAL RIVER RIVER LAKE LAKE SPECIES SPECIES w t % x 109 mg/1 k g x 109 mg/1 kg x 109

C a 6.7 9.45 11.0 0.038 Na 0.37 0.285

Mg 1.48 2.09 136.0 0.480 K 1.45 1.12

N a 4.0 5.64 3120.0 11.0 Ca 1.37 1.05

K 0.68 0.96 166.0 0.586 Mg 2.0 1.54

Cl 0.9 1.27 2257.0 7.97

U 0.0007 0.001 0.13 0.0005

TABLE 6. Masses of Ca, Mg, Na, K, Cl, and U derived from river, and in solution in the lake.

Total flux from river estimated at 1.41 x 1015 1; present lake volume estimated at

3.53 x 1012 1. Total detrital clay estimate of 7.7 x 10^9 kg is frcm total clay

estimate in sediments. 53

three subareas, as shown in Figure 31. Subareas A and B were esti­ mated to contain five m of sediment deposited since the last dessica-

tion of the lake, based on a sedimentation rate of one mm/yr, and

the data for core G. Subarea C was estimated to contain no sediment.

The sediment in subarea B has probably been overestimated, and sub-

area C underestimated; it is hoped that the two will compensate.

The subareas were then divided into ten subvolumes each. The

data in Table 3 for weight percent water, and the analytical data

for cores G and B, were used to determine the mass of each species

in solution in the pore fluids of subareas A and B respectively;

the results are given in Table 7. The estimates of Ca and Mg in the

carbonate minerals, based on the data from Table 3, are given in

Table 8. The Na, K, Ca, and Mg in the clay fraction are also given

in Table 8. The estimates are based on the bulk clay chemistry for

core G; in subarea B the clays were assumed to contain Ca as the

dominant exchange cation, based on the pore fluid data for Ca and

Na (Figures 3, 4, 13, and 14). Figiire 31. Subareas used in salt budget calculations. SUBAREA k g H^O kg Ca kg Mg k g N a kg K kg Cl kg U lrt10 DEPTH (m) x 10 x 106 x 106 X 10 x 107 x 108 x 10

A 0-0.25 0.84 0.17 1.05 0.25 0.15 0.25 1.01 A 0.25-0.75 1.69 0.42 0.76 0.67 0.35 0.64 1.18 A 0.75-1.25 1.69 0.34 0.25 1.01 0.37 0.87 0.85 A 1.25-1.75 1.68 1.43 0.41 1.13 0.50 A 1.75-2.25 1.68 1.68 0.51 1.39 0.17

A 2.25-2.75 1.66 2.00 0.64 1.75 A 2.75-3.25 1.46 2.19 0.67 1.87 A 3.25-3.75 1.33 2.40 0.80 2.11 A 3.75-4.25 1.42 3.12 0.96 2.59 A 4.25-5.00 2.41 5.55 1.70 4.62

B 0-0.25 1.46 0.20 1.82 4.37 0.18 0.28 ' 1.10 B 0.25-0.75 2.93 0.88 2.49 6.44 0.34 0.29 1.17 B 0.75-1.25 2.90 1.45 2.03 5.07 0.19 0.09 0.58 B 1.25-1.75 2.91 1.45 1.46 4.37 0.16 0.03 0.29 B 1.75-2.25 2.90 1.45 1.16 3.63 0.13 0.02

B 2.25-2.75 2.88 1.44 0.87 2.88 B 2.75-3.25 2.53 1.27 0.51 1.90 B 3.25-3.75 2.31 1.15 , 0.23 1.15 B 3.75-4.25 2.46 1.23 0.12 0.62 B 4.25-4.75 4.18 2.09 0.21

TOTAL 13.5 13.0 23.3 7.55 17.9 6.85

TABLE 7. Masses of species in solution in the pore fluids.

Ln Ui SUBAREA kg SOLID k g C a in kg M g in k g C a in kg M g in k g N a in k g k in DEPTH (m) CALCITE CALCITE CLAYS CLAYS CLAYS CLAYS 1A10 x 10 x 109 x 107 x 107 X 107 x 107 x 107

A 0-0.25 0.132 0.111 0.30 2.69 0.39 0.60 A 0.25-0.75 0.322 0.231 0.324 0.68 4.65 1.90 1.98 A 0.75-1.25 0.395 0.257 1.57 2.14 4.08 0.96 2.27 A 1.25-1.75 0.460 0.323 3.31 2.91 4.56 1.35 2.85 A 1.75-2.25 0.544 0.612 3.05 2.63 5.51 2 . 2 0 3.94

A 2.25-2.75 0.615 0.657 2.48 1.23 4.43 1.32 2.74 A 2.75-3.25 1.30 0.649 2.34 10.8 3.13 5.77 A 3.25-3.75 1.63 1.56 4.55 18.2 6.37 4.08 A 3.75-4.25 1.42 1.25 4.34 15.3 6.71 8.58 A 4.25-5.00 1.30 1.19 7.64 17.8 2.76 9.32

B 0-0.25 0.180 0.147 0.41 3.68 0.54 0.82 B 0.25-0.75 0.642 0.445 2.04 1.84 9.53 1.83 4.05 B 0.75-1.25 0.966 0.581 3.90 4.14 9.97 0.86 5.55 B 1.25-1.75 0.797 0.560 5.74 3.59 7.91 0.75 4.94 B 1.75-2.25 0.943 1.06 5.29 4.25 9.56 0.88 6.83

B 2.25-2.75 1.07 1.14 4.30 2.29 7.68 0.47 4.75 B 2.75-3.25 2.25 1.12 4.82 18.7 1.00 10.0 B 3.25-3.75 2.82 2.71 9.37 31.6 1.95 7.08 B 3.75-4.25 2.46 2.17 9.24 26.5 1.92 14.9 B 4.25-4.75 2.25 2.07 11.3 30.9 2.35 16.2

TOTAL 22.5 18.9 32.0 80.1 244.0 39.6 117.0

TABLE 8. Masses of species in carbonate and clay minerals in the sediment. 57

INTERPRETATION AND DISCUSSION

AQUEOUS PHASE

Saturation data for lake water (Table 2) indicate that Ca/Mg- carbonate phases are the only minerals which would be expected to form authigenically. Dissolved Si02 is kept at low levels by the activity of diatoms, therefore precluding the formation of large amounts of silicates. + 4- — 2*- The concentrations of Na , K , Cl , S04 , and C (Figures 3-12) in pore fluids increase with depth in cores C, D, E (lower portion) ,

F, and G. However, the pore fluids remain undersaturated with respect to chloride and sulfate minerals. In core 3 and the 'upper portion of core E, there is a general decrease in Na+ , K' , Cl , SO^, and C (Figures 3, 5, 7, 9, and 11) with depth. Both types of con­ centration gradients are interpreted as being due to the diffusion of ions from areas of higher concentration to areas of lower con­ centration. In cores C, D, E (lower portion) , F, and G the dissolu­ tion of evaporite minerals deposited during a previous period of desiccation (Benson, 1977) causes the transfer of dissolved solids frcin the sediments to the overlying water mass. Where the evapc- rites are not present (at the lake periphery) , the transfer of mass is from the lake to the sediments.

Sulfate is being removed from solution by reduction to sulfide; the reduction cf organic carbon is an additional source of C in Jne 58

pore fluids. Potassium concentration gradients (Figure 5) indicate that chemical reactions involving K+ are also occurring.

Pore fluid data indicate an upward diffusion of Ca2~ (Figure 13) in core B and the upper portion of E. This is interpreted as the result of dissolution of carbonate minerals deposited during a prior low stand of Walker Lake. An initial increase of dissolved 2+ Ca occurs in cores C, D, F, and G (Figures 13 and 14) ; with in-

2+ 7+ creasing depth, dissolved Ca decreases. Dissolved Mg decreases with depth in each of the cores (Figures 15 and 15) ; the decrease being more rapid in cores C, D, F, and G. In general, the concen- 2+ tration gradients indicate removal of Mg from overlying lake water and interstitial fluids.

Dissolved silica increases with depth in the upper portion of the cores (Figures 17 and 18) . In the < 2 m cores the Si02 ^ ^ con- -3 centration levels off at an activity of ^ 10 . In core G the

Si02 activity increases to v 10-3 at 2 m, then decreases to 3.5, and 3+ 2+ ■ then increases again (Figure 18) . Both A1 and Fe increase m the upper portions of certain cores (Figures 21 and 22) ; this may indicate the dissolution of detrital silicates.

SOLID PHASES

Monohydrocalcite has been observed in the lake sediments and as an encrustation along the shoreline (Figure 32) . The upper 1-1.5 m of sediment generally contains monohydrocalcite. There is a general decrease of the mineral with depth (Table 3 and Figures 24 and 25) .

In the upper 1-1.5 m calcites containing 10-12 mole percent MgC03 Figure 32. Monohydrocalcite precipitate (bottom) and

encrustation (top). 6

are also found, and generally increase in abundance with depth

(Table 3 and Figures 24 and 25) . Below 1.5 m in core G the percent

MgCO^ in the calcites decreases with depth, and below 2.5 m the calcites contain < 3 mole percent MgCO^.

It is thought that monohydrocalcite formed hirst and that cal- cite has formed diagenetically from them. The low-Mg-calcite .found in the lower portion of the cores may be a primary precipitate or it may be a recrystallized monohydrocalcite or high-Mg-calcite. Petro­ graphic examination of this portion of sediment (1.5-4.5 m, core G) indicate variable birefringence (Figure 33) and uniaxial-biaxial interference figures within single grains, suggesting strain in the calcite lattice. This suggests that a metastable carbonate phase has since recrystallized to calcite.

The silicate minerals at Walker Lake are primarily quartz, feldspars, and various clay minerals (Table 3). Microscopic exami­ nation indicates the quartz and feldspars are of detrital origin; sharp edges and fractures have been preserved (Figure 34). Diatom frustules are abundant throughout all of the cores, and appear relatively unaltered (Figure 34).

The clay minerals consist almost entirely of a randomly mixed- layer smectite-iliite phase. The smectite-illite may be detrital or authiqenic. The smectites account for between 55 and 83 percent and illites from 12-30 percent of the clay minerals. River clays are similar to these found in the sediment.

Malar ratios of the structural components of the clay fraction Figure 33. Calcium carbonate grain mounts under crossed

p o l a r s ; G 0.4 m (top) m o n o h y d r o c a l c i t e ,

G 4.5 m (bottom) calcite. 62

Figure 34. Detrital sediment (top) and diatom frustules

(bottom) from 4.5 m in core G. 63

of core G are presented in Table 9. The ratios Fe/SiO.,, Al/SiC^, and Fe/Al are nearly constant with depth. The Fe/Si02 ratios from

dredge sample are high, and the Al/Si02 from 0.4 m is low in relation to the others. The ratios involving Mg change with depth, decreasing fron the surface to 2 m, increasing to 3 m, and then decreasing again. The trend in exchangeable cation charge per mole

SiC>2 parallels the Mg ratio trends.

The chemical data frcm Table 4 was used to construct structural smectite-illite formulas after the methods of Ross and Hendricks

(1945) . These formulas are given in Table 10. Iron was assured to be in the ferric state. The sediment contained H2S at the time of collection. Rozenson and Heller-Kallai (1976) found that Fe in smectites was reduced in the presence of sulfide solutions; thus a portion of the Fe is therefore probably in the ferrous state. As a result, the layer charge calculated in Table 10 is probably low.

With the exception of the upper portion of sediment, the ratios involving Fe, Al, and Si02 (Table 9) are nearly constant. This indicates that below the depth of about 1 m clay minerals are not forming, or at least are not forming in large quantities.

In the upper portion of sediment, the formulas in Table 10 do not conform well to structurally ideal clay; the layer charge dir- fers greatly from the interlayer charge, and the number of octahedral cations calculated in the dredge sample » 2.0. This suggests that a portion of the < 0.2 y fraction was either organic or Al/Fe oxy- nydroxides. Excess of Mg in the clay fraction of the upper 0 . 5 m SAMPLE

DEPTH (m) Mg/Si Fe/Si Al/Si Mg/Al Fe/Al Mg/Fe Int- Ch./Si K/Si

DREDGE 0.37 0.15 0.35 1.05 0.43 2.42 0.17 0.05

G 0.4 0.15 0.11 0.29 0.54 0.37 1.44 0.14 0.04

G 1.0 0.11 0.13 0.36 0.31 0.35 0.88 0.16 0.04

G 1.5 0.09 0.10 0.32 0.29 0.33 0.89 0.15 0.04

G 2.0 0.11 0.14 0.38 0.30 0.37 0.81 0.17 0.05

G 3.0 0.21 0.14 0.35 0.59 0.39 1.46 0.20 0.07

G 4.0 0.15 0.13 0.36 0.42 0.37 1.16 0.19 0.05

G 4.5 0.13 0.12 0.33 0.39 0.36 1.10 0.15 0.05

TABLE 9. Molar ratios of components determined in the < 0.2 p size fraction from core G.

("Int. Ch." equals interlayer charge.) SAMPLE SMECTITE-ILLITE LAYER OCT O C T SITES TET SITES INTERLAYER CHARGE IONS

DREDGE (Al3+ Fe3+ Mq^+ ) (Al3+ Si4+ ) 0.5 8x+ 1.84 2.41 ' 0.63 0.51 ^1.27; l^0.57b 3.43;

G 0.4 (Al3+ Si4+ ) 0.55x+ 0.69 2.05 ( M 1.03Fe0.43Mg0.59) ^ 0.10bl3.90; 3+ „. 4+ . G 1.0 0.60x+ 0.65 2.01 ( M l.llFe0.49Mg0.41) ( M 0.24Sl3.76)

G 1.5 (Al3+ Fe3+ Mq2+ ) 0.59x+ 0.42 1.93 ' 1.19* e0.39^0.35; (M0.07Sl3.93) ,A 3+ _ 3+ .. 2+ . G 2.0 (Al3+ Si4+ ) 0.63x+ 0.71 2.04 (A1l.llFe0.52Mg0.41) ^0.30b 3.70J

G 3.0 (Al3+ Fe3 1 M cj2+ ) (A23+ Si4+ ) 0.72x+ 1.15 2.14 1 0.87 0.51^0.76^ ^0.39^3.61;

G 4.0 (Al3+ Fe3h M q 2+ ) (Ai3+ si4+ ) 0.70x+ 0.86 2.05 v 1.02 e 0.48 ^ 0 . 5 5 ; UU0.31b 3.69J

G 4.5 (Al3+ si4+ ) 0.57x+ 0.68 2.04 (A11.08^0.46^0.50} 1 0.18‘ 3.82;

TABLE 10. Calculated structural formulas for the < 0.2 y size fraction of core G. 66

of sediment is also probably present as either organic material

(e. g. chlorophyll A), or as oxy-hydroxide.

At 2 m there is a slight increase in the proportion of potassic

layers (Table 9) , which is even more evident in the 3 m sample. The

progressive increase of K layers from 4.5-2.5 m is also reflected in

the amount of exchangeable K+ (Figure 30) . The sanples which contain

higher proportions of K also show corresponding increases in Ma

(Table 9) . The calculated layer charges between 2.0 and 4.5 m

(Table 10) , are high, relative to the interlayer charge. This also

indicates the presence of material which is not a part of the mixed-

layer structure, e. g. , brucite. The presence of brucite layers is

supported by XPD data; the smectite 001 peak did not readily collapse

to 10 A upon heating.

The low CSC (Figure 28) in the upper 0.05 m of sediment appears

to be more a function of dilution of the mixed layer clay by other material in the clay fraction than a decrease in the CEC. The major

part of the exchange capacity is presumably due to the smectite

portion of the mixed-layer clay. The exchange stemming frcm the

illite layers is represented by exchangeable K+ (Figure 30) . The

upper 2 m of sediment contain roughly the same proportion of ex­

changeable K+ as the river clays. + 2+ The principal exchangeable cations found were Na and Ca (Figure 29) . The river clays are relatively high in exchangeable

Ca2+, while the clays in the lake are higher in Na' . However, in the

upper portion of core G, Ca2+ replaces Na+ as the principal exchange­

able cation. 67

CARBONATE SYSTEM

At present, monohydrocalcite is being precipitated from the

lake, although it is metastable with respect to dolcmite, calcite, and aragonite. The formation of metastable carbonate phases is common in nature (de Boer, 1977; Berner, 1975) .

Dolomite should form in Walker Lake. Berner (1971) concluded that dolomite is kinetically inhibited from forming in sea water.

It is likely that at Walker Lake dolomite is also kinetically inhib­

ited. Calcite is the next most stable form of carbonate in Walker

Lake. Several authors who have investigated the carbonate system

(Bischoff, 1968; Berner, 1974; Folk, 1974) have found that rela­ tively high Mg/Ca molar ratios (> 2) in solution will inhibit the

formation of calcite. At Walker Lake the Mg/Ca ratio is 20, and this probably inhibits calcite formation.

Synthesis of monohydrccalcite has been accomplished in solutions where magnesium chloride or sodium polyphosphate was added to sea water (Brooks et al, 1950; van Tassel, 1962), and from solutions with high Mg/Ca ratios (Hardie, personal canmunication). This indicates

that high Mg/Ca ratios also inhibits the formation of aragonite. In

Walker Lake the Mg/Ca ratio in solution is v 20:1. It is suggested

that this high Mg/Ca ratio inhibits the formation of the more stable

carbonates, allowing monohydrocalcite to form (reaction (A))

Ca2+ + C032' + H,0 = CaCCy H20 (A)

The pH in the upper portion of sediment, is significantly lower 68

than that of the lake (Figures 19 and 20) . In determining the

extent of the pH charge, the HCO^ -CO^ buffer capacity must be considered (B) :

HC03“ = C032' + H+ (B)

The mass action equation (C)

[C032"] [H+ ] K = (C) [h c o 3"] may be used to evaluate the extent of reation (B) . The pH in the

lake water is 9.5 - .2, and the average pore fluid pH at 0.05 m is

-10 33 2- - ^ 8.8, K for the reaction is 10 ’ . The C03 -HC03 ratios are then given by (D) and (E)

(D) [h c o 3- ]

(E) [h c o 3“ ]

respectively for lake water, and pore fluid at 0.05 m. If, for sim­ plicity, activity is assumed to equal molality, equation (F) may oe solved from the analytical molality of carbon in the lake (0.039) and

in the upper 0.05 m of sediment 0.044) , using the relations in

(D) and (E).

mcarbon = ir‘HC03 + (F) T /

69

The lake waters contain v 0.005 m / 1 CO 2~, and v 0.034 m/1 HCO ~.

The pore fluids at 0.05 m contain ^ 0.001 m/1 C032" and v 0.043 m/1

HC03“. This indicates v 0.004 m/1 C032- have reacted to form HC03"

through equation (D) , and that v 0.005 m/1 HC03“ have been added to

the system. From equation (D) v 0.004 m/1 of H+ must have been

produced/added to accomplish the observed change in pH. 2- Biologic reduction of SO^ and carbonaceous organic material

(CH20) in the sediment may account for the change in pH (G) .

SO 2" + 2CH 0 b^ 1°g1C> 2H+ + S2_ + 2HCO.~ 4 2 reduction

The lake waters contain v 0.022 m/1 SO^ and the pore fluids 0.019

m/1 at 0.05 m; sulfide was noted in all of the core sections. Assum-

2- ing that the decrease in SO^ is entirely due to (G) , ^ 0.006 m/1

+ 2— — H , % 0.003 m/1 S , and v 0.006 m/1 HC03 would be produced. The

H_r", S2_ and KC03” produced through reaction (G) agree well with the

observed trends in pH and HCC>3 .

In the upper 1-1.5 m of sediment, the pH is probably buffered

by the dissolution of monohydrocalcite (H)

CaCC>3 • H 20 + H+ = C a 2+ + HC03" + H 20

which accounts for the increase of Ca in the upper portions O j.

cores C, D, F, and G (Figures 13 and 14). The addition of HCO

through reaction (H) is insignificant relative to the high concen­

trations of HC03 already in solution.

As shown in Figures 24 and 25, monohydrocalcite is present 70

throughout cores C and D, and in core G to a depth of 1 m. The logarithms of the ion activity products (log IAP) of CaC03 for these core sections range from -7.47 to -6.97 (Figure 27), with an analyti­ cal uncertainty of - 0.05. The log I A P ^ for the lake water is

-7.07 - 0.05.

In the lake, saturation with monohydrocalcite is being approached from an oversaturated state through precipitation. However, in the pore fluids, saturation is being approached through dissolution of the mineral where it is present. The log LAP values in the pore fluids approach that of the lake water, indicating a log K for mono­ hydrocalcite of approximately -7.07. This is not in good agreement with log K, determined using the thermochemical data of Hull and

Turnbull (1973) , of -7.46. The data for the upper part of core C is in good agreement with the Hull and Turnbull data. These core sec­ tions may, however, be undersaturated with respect to monohydrocal­ cite, if the rate of pH decrease is greater than that of monohydro­ calcite dissolution.

The Mg/Ca ratios decrease in the pore fluids with depth. The log LAP_ w from 0.45 and 0.95 m in core G are controlled by monohv- ^ Ca-Mg drocalcite dissolution. At these Ca/Hg ratios, a calcite containing about 10 mole percent MgC03 should form from solution (de Boer, 1977) .

The Mg content of the calcites in this area is about 10 mole percent

(Table 3) . Dolomite is still the most stable form of Ca-Mg carbonates in this region, but is kinetically destabilized.

At 1.45 m in core G, monohydrocalcite is no longer present. As 71

shewn in rigure 27, the waters are highly supersaturated with re­ spect to calcite. The high degree of supersaturation in the pore fluids where monohydrocalcite is not present may be due to phosphate inhibition of calcite formation.

The Mg/Ca ratio in the pore fluids decreases below 1.45 m, causing calcites with lower Mg content to be stabilized. The cal- cites found in the sediment conform to this model; the Mg content of the calcites decreases with depth (Table 3).

SILICATE SYSTEM

In Walker Lake the activity of SiC>2 is controlled by the diatom activity. In the sediment, SiC>2 concentrations appear to be in- 24- versely related to Mg with depth. Silica concentrations in core

G (Figure 18) increase in the upper 2 m; Mg in this region (Figure

16) decreases with depth. From 2-3.4 m SiC>2 ^ ^ decreases; in this region, Mg is being released from calcites. Below 3.5 m the calcite

Mg source is no longer present, and Si02 ^ ^ increases.

24- 4-2 Core G pore fluids are plotted on a Mg /(H) vs H^SiO^ activity diagram in Figure 35. At 0.45 m the pore fluid compositions plot within the Mg-montmorillonite field. This indicates that dia- genetic clay formation, or dissolution of detrital clays, may control

SiCL , . and M cj2+ in solution in this region. However, it appears 2 (aq) that Mg is leaving the clay fraction in this region, but that silica is not, indicating separate controls. The increase of Si02 (Figure

18) may be controlled by the kinetics of diatom and/or primary sili- cate weathering in the upper 2 m. The change in Mg is probably due iue 5 Atvt-ciiy iga ; s e t a c i l i s - g M diagram Activity-activity 35. Figure log [Mg2‘] / j y ] 2 rm egsn t l (1969). al et Helgeson from o [4 04] i0 [H4S log 7 2 73

to carbonate, rather than silicate controls. Frcm 2-3.5 m f the pore fluids remain within the montmorillonite (smectite) field; in this 2+ region, Si02 ^ j and Mg are probably controlled by the formation of diagenetic smectite—illite clays. Magnesium is derived from the cal- cites, and silica from diatom and/or primary silicate weathering.

Below 3.5 m the pore fluids remain undersaturated with amorphous silica, and within the montmorillonite field. The carbonate source of Mg is no longer present; Si02 ^ ^ increases due to diatcm and/or primary silicate weathering, as seen in Figure 18, but the activities are still controlled by the smectite-illite formation. The amount of diagenetic clay formed is probably minor with respect to the detrital component, but sufficient to control dissolved SiC>2 and

Mg2+ below 2 m.

The pore fluid data for Fe and A1 frcm cores B, C, D, and E

(Figures 22 and 21) indicate a source of Fe and A1 to solution in the upper 0.5 m of sediment. This is probably the result of dissolution of oxy-hydroxides present in the clay fraction. The Fe and A1 in the pore fluids (Figures 22 and 21) is removed between 0.5 and 1.0 m.

The Al appears to enter the smectite-illite structure, possibly reolacina Mg. The iron is probably removed frcm solution to form

Fe-sulfides.

The interlayer cations, Na and Ca , change significantly from the river to the lake. The river clays are high in exchangeable

Ca2+, while the lake clays are high in Na (Table 1). The exchange reaction (I) 74

2Na+ + Ca(clay) = N a 2 (clay) + C a 2+ (I) is a function of relative concentrations of Ca2+ and Na+ . As the

Na/Ca ratio in the fluid increases, so must the Na/Ca ratio on the exchange sites. 2+ The increase of Ca in solution in the upper metre of sediment

(Figure 14) causes reaction (I) to go from right to left. Calcium replaces sodium as the dominant exchangeable cation in this region.

With increasing depth, the Na/Ca ratio in solution increases (Fig­ ures 4 and 14) , and reaction (I) proceeds to the right. The rela­ tively high Ca content at 4.5 m , core G, does not fit this model.

This is the area of highest Na/Ca ratio in solution, and these clays have been exposed to this environment for the longest period. There 2M is apparently a source of Ca in the region, or an error in the + 2+ exchangeable Na and Ca“ determinations. -

In core G fixation of potassium in interlayer positions occurs at about 3 m in the sediment (J) .

Na, Ca [smectite] = K [illite] (J)

The K fixation is controlled primarily by the layer charge (Table 10), rather than by the concentration in solution (Figure 6) . An in­ creased layer charge favors K^" in interlayer positions (Weaver and

Pollard, 1973); the K+ is fixed and the clay structure collapses fron 14-10 A, going from a smectite to an illite. The increased layer charge appears to be a function of Mg availability.

The processes acting in the sediment of core G occur in the other portions of the lake as well. There are, however, some notable

2+ exceptions. Where Ca increases with depth (Figure 13, cores B and E) , and Na decreases (Figure 3, cores B and E) , Ca may be the major exchangeable cation. In this portion of the lake, the Mg^+ gradient (Figure 15, cores B and E) is not as sharp as in the G core. Although the K+ in solution (Figure 5, cores B and E) is lower, fixation of K+ may occur to a greater extent in this region, due to the availability of Mg to structural clay sites.

SALT BUDGETS

The results of the salt budget calculations are summarized in

Table 11. The calculations are based on estimated river concentra­ tions, volume flux, and mass calculations of the various ionic species in lake water, sediment, and pore fluids. The lake is assumed to have started filling 5,000 yrs B. P. (Benson, 1977) .

The river concentrations are based on recent data on the upper

Walker River. Concentrations vary between periods of high and low flow. A weighted average (80 percent high flow, 20 percent lev/ flow) has been used to estimate past river concentrations. The contents of the lower 3-4 m of sediment have been estimated from the data on only one core (G).

The pore fluid data for Na^, K+ , and Cl- (Figures 3, 4, 5, 6,

7, and 8) in cores C, D, F, and G indicate a source O j. these salts below this portion of the lake. The salt budgets gave seme indica- __ 24* tion as to the importance of this source to the system. The Ca SOURCES SINKS

RIVER DETRITAL TOTAL LAKE PORE CARBONATE CLAY TOTAL SPECIES INPUT CLAY INPUT FLUID SINKS

C a 9.45 1.05 10.5 0.038 0.0135 18.9 0.80 19.7

Mg 2.09 1.54 3.63 0.480 0.0130 0.32 2.44 3.25

N a 5.64 0.29 5.93 11.0 2.33 6.40 13.7

K 0.96 1.12 2.08 0.586 0.0755 1.17 1.83

Cl 1.27 1.27 7.97 1.79 9.76

U 0.001 0.001 0.0005 0.0000069 0.0005

TABLE 11. Sources and sinks determined for salt budgets; all values are kg x 109 . 77

2+ source of Ca to solution in this portion of the lake. Calcium may also have been derived fran the dissolution of carbonate minerals deposited during the decline of a preexisting lake within the basin.

Magnesium does not appear to be added to the sediment-water system via the dissolution of former evaporite deposits (Figures 15 and 16).

If the clay in the sediment is assumed detrital, and the detri- tal clay to contain 2.0 percent MgO by weight, the total sinks, solids and fluids, account for 90 percent of the estimated Mg flux.

The major Mg sink is the clay minerals; minor sinks are the lake water and the carbonate minerals (Table 11). The formation of authigenic or diagenetic clays may account for an overestimate in the detrital clay input.

The salt budget for U shows that about 50 percent of the total estimated flux frcm the river remains in the lake water. Uranium

in solution in the pore fluids is relatively minor, and decreases with depth.

The estimated Ca input accounts for only 53 percent of the total

Ca in the lake and sediment. The Ca is primarily tied up in car­ bonate minerals. This indicates a significant source of Ca within the basin.

The budget calculations for Na and Cl also indicate a signif­

icant input frcm salts within the basin. The river flux accounts

for only 13 percent of the Cl in the lake and sediment. The flux of

Na frcm the river accounts for only 43 percent or the total Na. The

K in the lake and sediment accounts for v 90 percent of the

estimated input. 78

SUMMARY AND CONCLUSIONS

The overall chemical composition of Walker Lake is largely the result of the dissolution of evaporite minerals deposited during the decline and desiccation of a preexisting lake. The salt budgets indicate that approximately 60 percent of the Na, 50 percent of the

Ca, and 90 percent of the Cl in the lake and associated sediments were derived from evaporite salts within the lake basin. Concentra­ tion gradients in the deep lake cores also indicate a source of K

(Figures 5 and 6) , SO^ (Figures 9 and 10) , and C (Figures 11 and 12) , within the evaporite deposits.

The major source of water to the lake has been the Walker River.

A large portion of the detrital sediment, and of the remaining dis­ solved species, have also been derived from the river.

The dissolved constituents, derived from both-the evaporite min­ erals and from the river, have subsequently been concentrated through evaporation. Certain constituents have been altered through biologic activity and mineral precipitation. Calcium has been removed from solution in the lake through the precipitation of carbonate min­ erals . H e carbonate minerals in the sediment consist of calcite in the lower portion, and calcites containing Mg, and monohydrocal- cite in the upper portion. At the present, mcnohydrocalcite is be­ ing formed; the calcites in the upper portion of the sediment have formed from preexisting monohydrocalcite. It is possible that all 79

of the calcites were originally monohydrocalcite.

Magnesium has also been removed frcm solution, but to a lesser extent than calcium. In the upper portion of sediment, M g 2+ is removed frcm solution through the formation of Mg containing cal­ cites . Magnesium has also been removed from solution through the formation and alteration of clay minerals. In the lower sediment, brucite layers may be present in the smectite-illite. In the uppermost sediment, the clay fraction contains a high proportion of

Mg, both as a result of Mg in the clay structure, and as either a hydroxide or an organic precipitate.

Sodium and potassium have been removed from solution, but to a minor extent, through cation exchange and fixation by clay min­ erals . The result has been to greatly increase Na+ and K+ in sol-

24- 2+ ution, relative to Ca and Mg , resulting in the formation of a sodium lake.

- - 2 - The major anion species in the lake are Cl , HCO^ , and S0^“ .

The chloride has been primarily derived frcm the evaporite minerals, and concentrated through evaporation. The evaporite minerals are also a major source of SO^ and HCO^. Carbon is removed frcm solu­ tion in the formation of Ca-Mg-carbonate minerals. There is also an addition of C to the system through biologic activity. Sulfate is removed from solution through biologic reduction.

The major anionic composition of the lake is thersj-ore princi­ pally a result of the dissolution of the evaporite minerals in the basin. Due to chemical precipitation of carbonates and biologic 80

reduction of aulfate, the relative abundance of chloride has in­

creased in the lake.

SEDIMENT-WATER REACTIONS

A series of pertinent reactions occurring within the lake and

sediment are listed in Table 12. These reactions do not necessarily

occur in all portions of the system, but are important in some in­

stances.

The reactions occurring within the lake are the formation of monohydrocalcite (1) frcm solution, and the exchange of Na for Ca

in smectites (5) . Silica is removed frcm solution in the lake

through biologic activity (reaction (9)). Detrital material has been added to the lake as sediment. Chemical changes in the detri­

tal material, such as silicate hydrolysis (8) , are probably minor.

Dissolution of monohydrocalcite (2) occurs in the upper few metres of sediment as a result of a lower pH, due to biologic re­

duction (15) . Monohydrocalcite is destabilized in the upper few

metres of sediment, due to changing Mg/Ca ratios. Magnesium-cal-

cites are forming in this region. The calcites are thought to be

the primary sink for Mg in this portion of sediment. The increase

in Ca2+ in solution caused by monohydrocalcite dissolution (2)

causes Ca to substitute for Na in exchangeable cation sites, (5).

The change in pH may also cause Fe (12) or A1 hydroxides (13) to go

into solution. The hydroxides are probably of detrital origin, and

a portion of the clay fraction. Iron is removed frcm solution to

form Fe-sulfides (14) and Al may replace Mg and/or Si in smectites 81

REACTION NUMBER REACTION

(1) Ca2+ + C032- + H20 = CaC03- H20

(2) H+ + CaC03 * H20 = Ca2+ + HC03“ + H20

(3) CaC03- H2o + Mg2+ = Ca(1. x ).% 003

(4) ^(l-xj^x00! + Ca2+ = CaC03 + Mg2+

+ 2+ (5) Ca(smectite) + Na = Na (smectite) + Ca

3+ (6) Al + (smectite-illite) = (smectite-illite) +

M g 2+ + H4Si04

(7) A l J+ + Mg2 ' + H 4Si04 = (smectite-illite)

(8 ) H 20 + C0 2 + (primary silicate) = (clay) + HC03 +

H 4Si04 + cation

(9) (diatom frustule) = H 4Si0 4

(10) co2 + h2o = (ch2o) + o2

(ID 0 o + (ch2o) = co2 + h2o .

(12) Fe (OH) 3 + H+ = F e 3_r + H 20

(13) Al (OH)3 + H+ = A l 3+ + H 20

2+ 2- (14) Fe + S“ = FeS2

(15) so,2- + ch2o = h2s + hco3“

TABLE 12. Sediment-water reactions. 82

(6) , -Orm new clays (7) . Dissolved SiC^ increases in the upper

few metres of sediment, due to diatom dissolution, (7) . Silica and magnesium may be controlled by equilibrium between clay minerals and

solution, (6) or (7).

With increasing depth in the sediment (v 1.5-3.5 m) , the Mg/Ca

ratio in solution decreases. This destabilizes the Mg containing

calcites, which are replaced by calcite (4) . Magnesium is incorpo­

rated in the clay fraction, either through the formation of new

clays (7) , or is incorporated as brucite-like layers in the smectite-

• . . 2+ lllite. In this region, Mg and SiC^ appear to be controlled in

solution by the clay phase. Exchange of Na for Ca (5) occurs in the portion of sediment underlain by the evaporite salts.

In the lower sediments (v 3.5-4.5 m) , K fixation occurs in the

smectites. This is due to an increased layer charge, primarily due

2+ to Mg incorporation in the clays. The Mg and SiC>2 in solution are

controlled by reaction with the smectite-illite phase (7) . The

carbonate phase present is calcite, which is stable in this region.

The pore fluids are highly supersaturated with respect to calcite,

possibly due to phosphate inhibition.

At some depth below the penetration of the core samples, dis­

solution of salts deposited from a preexisting lake is occurring.

In the more shallow portion of the lake, these appear to be pri­

marily Ca-carbonates. The deeper portion of the lake is underlain

by more soluble salts; the ions released from these salts then

diffuse upwards. 83

REFERENCES CITED

Berner R. A. (1971) Principles of Chemical Sedimentology, 240 op. McGraw-Hill.

Berner R. A. (1974) The role of magnesium in the crystal growth of calcite and aragonite. Geo. Cosmochim. Acta 39, 489-504.

Biscaye P. E. (1965) Mineralogy and sedimentation of recent deep- sea clay in the Atlantic Ocean and adjacent seas and oceans. Geol. Soc. Aner. Bull., v. 76, 803-832.

Bischoff J. L. (1968) Kinetics of calcite nucleation: magnesium ion inhibition and ionic strength catalysis. J. Geophys. Res. 73, 3315-3322.

Bischoff J. L., Clancy J. J., and Booth J. S. (1975) Magnesium removal in reducing marine sediments by cation exchange. Geochim. Cosmochim. Acta 39, 559-568.

Brooks R., Clark L. M., and Thurston E. F. (1950) Calcium carbonate and its hydrates. Phil. Trans. Roy. Soc. London, A, 243, 145-167.

Brown E., Skougstad M. W., and Fishman M. J. (1970) Techniques of Water-Resources Investigations of the United States Geological Survey. Methods for Collection and Analysis of Water Samples for Dissolved Minerals and Gases. U. S. Geol. Surv., 160 pp.

Carrol D. (1970) Clay Minerals: A Guide to Their X-ray Identifica­ tion. Geol. Soc. of Aner. Spec. Paper 126, 75 pp. de Boer R. B. (1977) Stability of Mg-Ca carbonates. Geochim. Cosmochim. Acta 41, 265-270.

Brever J. I. (1971a) Early diagenesis of clay minerals, Rio Aneca Basin, Mexico. J. Sediment. Petrol. 41(4), 982-994.

Drever J. I. (1971b) Magnesium-iron replacement in clay minerals in anoxic marine sediments. Science 172, 1334-1336.

Erwin J. W. (1970) Gravity Map of the Yerington, Como, Wabuska, and Wellington Quadrangles, Nevada. Nevada Bureau of Mines Map 39. 8

Eugster H. P. (1970) Chemistry and origin of the brines of Lake Magadi, Kenya. Mineral. Soc. Amer. Spec. Paper No. 3, 215-235.

Fsth j. H., Roberson, C. E., Polzer W. L. (1964) U. S. Geol. Surv. Water Supply Paper 1535-1, 170 pp.

Folk R. L. (1974) Hie natural history of crystalline calcium car­ bonate: effect of magnesium content and salinity. J. Sediment. Petrol. 44, 40-53.

Garrels R. M. and Mackenzie F. T. (1967) Origin of the chemical composition of some springs and lakes. Equilibrium Concepts in Natural Water Systems. Am. Chem. Soc., 222-242.

Grim R. E. (1953) Clay Mineralogy, 384 pp. McGraw-Hill.

Hardie L. A. and Eugster H. P. (1970) The evolution of closed basin brines. Mineral Soc. Amer. Spec. Paper No. 3, 273-290.

Hardie L. A. (1968) The origin of the recent non-marine evaporite deposit of Saline Valley, Inyo Co., Calif. Geochim. Cosmochim. Acta 32, 1279-1301.

Helgeson H. C., Brown T. H., and Deeper R. H. (1969) Handbook of Theoretical Activity Diagrams Depicting Chemical Equilibria in Geologic Systems Involving Aqueous Phase at One Atm. and 0° to 300°C. 253 pp. Freeman, Cooper, and Co.

Hull H. and Turnbull A. G. (1973) A thermochemical study of monohy- drocalcite. Geochim. Cosmcchim. Acta 37, 685-694.

Jones B. F. (1966) Geochemical evolution of closed basin waters in the western Great Basin. Northern Ohio Geol. Soc., Symp. Salt, 2nd, 181-200.

Jones B. F. (1965) The hydrology and mineralogy of Deep Springs lake, Inyo Co., Calif. U. S. Gaol. Surv. Prof. Paper 502-A, 56 pp.

Jones B. F., Eugster H. P., and Rettig S. L. (1977) Hydrochemistry of the Lake Magadi Basin, Kenya. Geochim. Cosmochim. Acta 41, 53-72.

Kalil E. K. and Goldhaber M. (1973) A sediment squeezer for removal of pore waters without air contact. J . Sediment. Petrol., 43(2), 553-557.

Katz A. (1973) The interaction of magnesium with calcite during crystcil growth a.t 25—90 C cind. ons cLtmosph0r6 . Goochiiru Cosmochim. Acta 37, 1563-1586. 85

Kerr P. F ., editor^ (1951) Preliminary Reports Reference Clay Minerals American Petroleum Institute, Research Project 49.

Lawrence Livermore laboratory (1976) Walker Basin Pilot Study (Uranium e t c . ) .

Phillips K. N. and Van Denburgh A. S. (1971) Hydrology and geochem­ istry of Abert, Summer, and Goose lakes, and other closed-basin lakes in south-central Oregon. U. S. Geol. Surv. Prof. Paper 502-B, 86 pp.

Plummer L. N., Jones B. F., and Truesdell A. H. (1976) WATEQF-A Fortran IV Version of WATEQF, A Computer Program for Calculating Chemical Equilibrium of Natural Waters. U. S. Geol. Surv., Water Resources Invest. 76-13.

Plummer L. N. and Mackenzie F. T. (1974) Predicting mineral solubil­ ity from rate data: application to the dissolution of magnesium calcites. Amer. J. Sci. 274, 61-83.

Ross D. C. (1961) Geology and Mineral Deposits of Mineral County, Nevada. Nevada Bureau of Mines Bull. 58, 98 pp.

Ross C. S. and Hendricks S. B. (1945) Minerals of the montmorillonite group. U. S. Geol. Surv. Prof. Paper 205-B, 79 pp.

Rozenson I. and Heller-Kallai L. (1976) Reduction and oxidation of FeJ_r in dioctahedral smectites-2: reduction with sodium sulphide solutions. Clays and Clay Min. 24, 243-288.

Sawhney B. L., Jackson M. L., and Corey R. B. (1959) Cation-exchange capacity determination of soils as influenced by the cation species. Soil Sci. 87-5, 243-248.

Shapiro L. (1975) Rapid analysis of silicate, carbonate, phosphate rocks. U. S. Geol. Surv. Bull. 1401, 43-47.

Sholkovitz E. (1973) Interstitial water chemistry of Santa Barbara Basin sediments. Geochim. Cosmochim. Acta 37, 2043-2073.

Taras M. J. et al (1971) Standard Methods for the Examination of Water and Wastewater. 13th ed. An. Pub. Health Ass. 874 pp.

Truesdell A. H. and Jones B. F. (1974) WATEQJ*, a Ccmputer Program for Calculating Chemical Equilibria of Natural Waters. J. Res. U. S. Geol. Surv. 2(2), 233-248. van Bennekcm A. J. and van der Gaast S. J. (1976) Possible clay structures in frustules of living diatcms. Geochim. OosmoJaim. Acta 40, 1149-1152. 86

Van Denburgh A. S. (1975) Solute balance at Abert and Summer Lakes, south-central Oregon. U. S. Geol. Surv. Prof. Paper 502-C, 29 pp.

Van Tassel R. (1962) Carbonatniederschlage aus gemischten calcium- magnesiumchloridlosungen. Z. Anorg. Allgem. Chem. 319, 107-112.

Weaver D. E. and Pollard L. D. (1973) The Chemistry of Clay Minerals. Developments in Sedimentology 15. 213 pp. Elsevier Scientific Publishing Co.

Winland H. D. (1969) Stability of calcium carbonate polymorphs in warm, shallow sea water. J. Sediment. Petrol. 39, 1579-1587. --•"vw--- ■

87

APPENDIX I NPEACT DH LOGKTO 1 KFE +3 9.7000 -13. 0130 2 KFEHt-2 20.1150 -15. b733 3 KFE3H* 13.2130 -9.3190 b KFE0H3 32.9950 -29.L580 5 KFESO ^ 15.9200 -8.3660 6 KFECL 1S.152G -11.60 00 7 KFECL2 0. C -10.9190 8 KFECL3 0.0 -11.9250 9 KFFSO 0.5600 2.2000 1C SIDSRITF -5.3280 -10.550 11 HA G.SESlf -6.1690 -A.9C00 12 OOLOMIiE -9.2800 -17.0000 13 CALCITE -2.5850 -8.L7Q0 lb KH3STO 8.9350 -9.S3Q0 15 KH2SI0 2S.71LQ -21.6190 16 KHPO^ -3.5300 12.3L60 17 KH2PCA -A.5200 19.5530 18 ANHYDRIT -3.7690 -L.6370 19 GYPSUM 0.2610 - b , 59GQ 2C 0RUCITE 0.8500 „ -11.bb70 21 CHRYSCTL 27.L300 -52.6270 22 ARAGON IT -2.9590 -3.3GG3 23 KMGF L.67L0 1.3200 Zb KCASO«t 1 • 50 0 C 2. 30 25 KMGOH 2.1^00 2.6000 26 TALC A5.110Q -62. bBbQ 39 hydmag -25.5200 -37.318 AO ADULAR 31.1A0 0 -21. L1L3 b l AL8ITE 26.2000 -18.3570 bZ ANORTH 17.6730 -20.6230 bZ ANALCH 18.3000 -13.5290 bb KMICA 67.9200 -51.3590 b 5 PHLOG 0.0 -63.5300 be ILLITE 0.0000 -37.6660 b7 KAOLIN b 3 . 7<+00 -37.6910 b a HALLOY bb, 6800 -32.8200 t*9 CHLOR 54.7600 -90.61QQ 50 ALUNIT 29.8200 -85.3200

PPENDIX TA9LE 1. WATEQF THERMOCHEMICAL CO (CONTINUED) (CONTINUED) I NREACT DH LCGKTO 51 GI8CRS 16.1900 -32.7810 52 30t.HM 11.5050 ' -33.C6G0 53 PYPOPH 57.9000 -L3. 88AO 5L PHILIP 0.0 -19.5600 55 ERION 0.0 :. G 56 NAHCOL 3.7200 -0.5^80 57 TRCNA -18.0000 -Q.7950 58 NATRON 15.7 L50 -1.3110 59 THRNAT -2.6020 Q. 1250 60 FLUOR 1.5300 -9.5370 61 MONTCA 58.5220 -L6.16 70 62 HALITE G.9180 1.5623 63 THENAR -0.5720 -0.1790 6L MIF A 91 18.9370 -1.1130 65 YACKIT 0 .C -A,6310 66 KHC03 3.5500 -IQ.3300 67 KNAC03 8.9110 l.OG 68 KNAHC03 0.0 -Q . 25 G 0 69 KNASOL 1L. 78 9C 0.750 70 KKSOL 3.0520 0.6L7Q 71

APPENDIX TA3LE 1. KATEQF THERMCCHEMICAL CONSTANTS (CONTINUED) (CONTINUED) I NREACT CH LOGKTO 101 KFEQH2 0.0 -20.1730 10 2 • KF EOH 3 0.0 -26.5710 103 KFEDHA 0.0 -3A.39A0 10 A KFE0H2 28.5650 -20.5700 10 5 VIVIAN 0.0 -36.0000 106 MAGNET -A G •6600 -9.5650 107 HEHATI - 30•c A50 -3.9920 106 MAGHEM 0.0 6.3700 109 GOETH 25.5550 - A A . 2000 110 GPEENA 0.0 -63. 1900 111 FE0H3A 0.0 A . 8350 112 ANNITE 6 2. A 8 0 0 -8 A,2A0Q 113 FYRITE 11.3030 - 1 8 . A8QQ 1 1 A HU N'T ITE -25.7600 -30.5100 115 GPEGITE 0.0 -17.9700 116 FESPPT 0.0 -3.9150 117 XFEH2P 0.0 2.7000 118 KCAPOA 3.1330 6.A590 119 KCAH2P 3. A 0 0 0 1. AG 80 120 KMGPOA 3.1000 5.5890 121 KMGH2P 3 . A 0 0 0 1. 5130 122 XLIOH A.6320 0 . 20 0 0 123 XLTSOA 0.0 0.6A0Q 12 A KNHAR 137.0550 119.0770 125 LAUMON 39.6100 -31.9600 126 KSFOH 1.1500 0.5200 127 KBAOH 1.7500 0.6AG0 126 XNHASQ 0.0 1.1100 129 KHCL 13.6300 -6.1000 130 KN ACL 0.0 -1.6020 131 KKCL o.: - 1 . 585G 132 KH2SOA 0.0 -1. OCOO 133 X02 SATO G.C -11.3850 13A XC02 -5.G0QC - 1 . A600 135 KFFHPO O.C 3.6000 136 KFEHP+ 0.0 -7.6130 137 AL0H3A 12.5900 -31.6100 138 ??EHNT 1G.AA3G -13. 06 CO 139 STRONT 2.3610 -9.2520 1A0 CELEST - 1 . 3 5Au -5.97 AO 1A1 3AFITE 6.1A10 -9. 7560 1A2 WITHERIT 6.9500 -5.56 50 1A3 STRENGIT -2.C30Q -26.AGO 0 1AA LEON 90.0700 -65.5700 1A5 KNA2SO -3.6570 1.5120 lit 6 NESQUE - A . 5510 -5.A209 1A7 ARTIN 0 .A9S0 -15.AO Q 0 1A8 X 0 2 AQ 33.A570 - 2 1 . A950 li»9 KW 13.3A5Q -13.5980 150 SEP PT 0.0 -37.2120

APPENDIX TABLE 1. WA7EQF THERMCCHi f-ICAL CONSTANTS (CONTINUED) 91

(CONTINUED) I NREACT DH tOGKTO 151 OIASP -15.4050 -32.4700 152 W1TRKT 26.1900 -28.2150 153 KFEHP2 0.0 - 7. 5630 154 KMN 3 + 25.7600 -25.5070 155 KMNCL + 0.0 0.6070 156 KMNCL2 0 .G 0.0410 157 *MNCL3- 0 ,c - G . 3D 50 158 KMNOH+ G • G 3.4490 159 K H N ( O H ) 3 •o.c 7.7820 150 KMNF + 0.G 0.3500 161 KMNS04 3.70Q0 1.70 80 162 KMNNQ 3i2 -0.3960 0.G593 163 KMNHC03+ O.C 1.7160 164 KHN04- 176.6200 127.6240 165 KMN04 — 150.0200 113.4409 166 KHNF++ G .0 150.0000 167 KHPN02 — 0 .0 -34.4400 168 MANG a NO -24.G250 17.9360 169 PYPOLUST -29.1800 15.5613 170 9I9NSITE G .0 18.0910 171 NUSTITE O.C 17. 5C40 172 9 1 X 3 YIT E -15.2450 -0.6110 173 HAUSMITE -2.6600 -15.2210 174 MN0H2 4.1000 -12.9120 175 MNOH 3 20.0900 -35.6440 176 MANGANIT C .0 -0.2380 177 RHOOOCHR -2.0790 -1C.5390 178 MNHCO 3 »2 141.4400 90.1910 179 MNCL2 -17.6220 6.7600 130 XNCL2.1W -7.1750 5.5220 131 MNC12 12 W 1.7100 3.9740 182 MNCL2.4W 17.3300 2.7100 18 3 TEPHRIl E -40.0600 23.1220 184 RHOOONIT -21.8350 9.5220 185 MNS GRN -10.6300 -13.3430 186 MN$04 -15.4300 2.6690 137 MN2S04,3 -39.C60Q -5.7110 188 H N 3 P 0 4 , 2 2.1200 -23.8273 189 MNHP04 0. G -12. 9470 190 MCNTNA 50.4510 -46.3420 191 MONT K 51.6210 -46« 6460 192 MONTHG 58.2150 -46.1970 193 MHCALC -1.79 -7.527

APPENDIX TA8LE 1. w a t e q f THERMOCHE m i c a l c o n s t a n t s 92

S P E CIES CHARGE AT. WT. CHA 1 CA 2 **Q . Q8Q0 6. C 2 MG 2*+. 312 G 6.5 3 NA 22.9898 *+.0 *+ K 1 39.1020 3.0 5 CL . -1 35. *+53 0 3.0 6 SO*+ -2 96.0616 *+.C 7 HC03 -1 61.0173 5. *+ 8 FE 2 55.8*+7 0 6.0 9 FE 3 5 5.8 *+7 0 9.0 10 FEOH 2 72.85*+*+ 5.0 11 FEOH 1 7 2 . 85*+9 5.0 12 FE (OH ) 3 -1 10 6.8690 5.0 13 FEHPO *♦ 1 151.8200 5.*+ 1*+ H2S A Q 0 3*+, 0 79 9 15 FES 0*+ 1 151.9086 16 F£CL 2 91.3000 17 anal H2S 0 3*+. 0 799 18 CO 3 -2 6 0 .0G9*+ 5 • *+ 19 MGOH 1 *+1.319*+ 6.5 20 MGF 1 *+3.310*+ *+.5 21 MGC03 AQ 0 5 *+. 321 *+ 0.0 22 MGHCO 3 1 85.3293 *+.0 23 MGS 0*+ AQ 0 120.3736 0.0 2*+ H*+S IO *+AQ 0 96.1155 0.0 25 H3SIO *+ -1 95.1075 *+. 0 26 H2SI0 *t -2 9 *+ . 0 99 5 5. *+ 27 CH -1 17.007*+ 3.5 28 FECL2 1 126.7530 5. 0 29 CAOH 1 57.087*+ 6.0 30 cahco 3 1 101.0973 6.0 31 CAC03 AQ 0 100.0890 0 . 0 32 CAS O** AQ 0 1 3 6 .1*+16 o.c 33 FECL3 0 162.2060 0.0 3*+ FESO*+ G 151.9C86 0.0 35 S IO 2 TOT 0 60 .0 S*+3 0.0 36 H3B03 AQ 0 61.8331 0 . Q 37 H2B03 -1 60.8251 2.5 38 NH3 A Q 0 17.0306 O.G 39 NH*+ 1 13.0386 2.5 *+0 HGPO*+ -1 119.283*+ 5.*+ *+i MGH2P 0*+ 1 121.2993 5.*+ *+2 NAC03 -1 82.9992 5.*+ *+3 NAHCO 3 0 S3.9909 0 . G *+*+ NAS 0*+ -1 119.051*+ 5. *+ *+ 5 PO*+ - 3 9*+. 971 *t 5.G *+6 KSO *+ -1 135.1636 5. *+ *+ 7 HPO*+ -2 95.979*+ 5.0 *+8 H2PO*+ -1 96.9873 5.*+ *+9 NA2CO 3 0 1 C 5 .9690 0 .0 50 NAHPC *+ -1 113.9692 5.*+ 51 AL 3 26 .9315 9.0 52 ALOH 2 *+3.9889 5.*+ 53 AL (OH ) 2 1 60 .9962 5.*+ 5*+ AL (OH )*+ -1 95.0110 *+. 5 5 5 ALF 2 *+5.5799 5.*+ 56 ALF2 1 6*+ . 978 3 5. *+ 57 A LF3 0 83.9767 O.G 53 ALP** -1 102.9751 *+.5 APPENDIX TABLE 2. WATEQF SPECIES, CHARGES» ATOMIC WIEGHTS AND QPSEYE-HUCKEL A VALU-S. (CONTINUED) 93

continued) SPECIES CHARGE AT. WT. OHA 59 ALS 0% 1 123.0%31 it.5 60 AL ( SO %) 2 - 1 219.1Q%7 '-+.5 61 KHP-0% -1 135.081**. 5.it 62 F -1 18.998% 3.5 63 HSO% -1 97.0696 %.5 6% H 1 1.0030 9.0 65 FEH2P C% 1 152.63%Q 5.% 66 H23 C ALC 0 3%.0799 0.0 6 7 HS -1 33.0720 3.5 53 S -2 32.0 6%0 5.0 69 NA2S0 % 0 1% 2 • 0%12 0.0 70 P02 0 31.9988 O.G 71 PCH% Q 16.0 %3G 0.0 72 A H20 0 13.0153 0.0 73 MGHPO % 0 120.291% 0.0 7% CAHPO % 0 136.059% G.G 75 C APO% -1 135.051% 5.% 76 CAH2P 0% 1 137.0673 5.% 77 FECOH ) 2 1 89.8616 5.% 78 FE ( OH ) 3 0 106.8689 0 . C 79 FE (OH ) % -1 123.8762 5.% 80 FE (OH ) 2 c 89.8616 G.G 31 LI 1 6.9 39 0 6.0 82 L10 H 0 23.9%6% O.G 83 l ISO% -1 1C3.0 0 06 5 . G 3% NH%CA LC 1 18.0386 2.5 85 N03 -1 62.0 Q%9 3.G 35 H2C03 Q 62.0253 0.0 37 B TCT 0 10 .8100 O.G 83 SR 2 87.6200 5.0 89 SROH 1 10%.627% 5.D 90 BA - 2 137.3%0 0 5 . G 9i EACH 1 15%.3%7% 5.0 92 NH% SO % - 1 11%.1002 5.0 93 hcl - 0 36.%610 0.0 9% NACL 0 58.%%2 8 0 .0 95 KCL 0 7%.5550 0.0 96 H2SC% 0 93.0775 0.0 97 KHS 0% 0 136.1716 O.G 98 ER -1 79.9090 %.0 99 FEH2P 0% 2 152.83%0 5.% 100 FEHPO % 0 151.8200 0.0 101 MN 2 5%•9%0 0 6.0 102 HN 3 5%.9%G 0 9.0 103 MNCL 1 90.3970 5.0 10% MNCL2 0 125 .85%0 0.0 105 MNCL3 -1 161.3110 5.0 105 MNOH 1 71.8%6 0 5. G 107 MN ( OH ) 3 -1 1G 5.96%0 5.0 ,FPENOIX TABLE 2. HATEQF S! IES, CHARGES, ATOMIC WIEGHTS ANO 0E9EYE-HUCKEL VALUES . I NREACT OH LOGKTO SOURCE 20 BRUCITE n.8503 -11.AA70 1.3 21 CHRYSOTL 27.A800 -52. 6270 1, A 2A KCASOA 1.5000 2.30 1.3 37 SEPIOLIT 26.5C00 -A0.63AC A ,9 3fi TALC A5.1100 -62. A6 A0 1.8 AO ADULAR 31.1AC 0 -21. A1A0 3,3 A1 ALBITE 26.2000 -1fi.8570 1,3 A 2 ANORTH 17.6760 -20.8280 1,3 A3 ANALCM 16.300 0 -13.5290 1,3 AA KNICA 67.52C0 -51.3590 A 6 ILLITE J . 0 0 0 0 -37.8660 U 3 A7 KAOLIN A9.7A00 -37.6910 1,3 51 GIBCRS 16.1900 -32.7810 1,3 53 PYROFH 57.9000 -A3.faBAO 5,5 61 MONT CA 58.8220 - A 6.1670 1,6 67 KN/.C03 8.9110 1.00 11 68 KNAHC03 0.0 - C. 28 00 15 65 KNASOA 1A.7890 0.75 C 1A 71 KMGC03 0.0580 3. 30 C ii 73 KMGSOA 1.2700 2. 30 12 75 KCAHC03 6.3310 1. 1A 0 11 138 PREHNT 10.A AO 0 -1 3. 0600 5,5 152 WAIRKT 26.1900 -26.2150 5,5 19C MONTNA 60.A510 -A6.3A20 1,6 191 MONT K 61.6210 -A6. 6Ab0 1,6 192 MO NT MG 56.2150 -A6.1970 1,6 193 MHCALC -1.79 - 7. 527

APPENDIX TABLE 3. CHANGES TO PLUMMER ET AL (1976) VERSION OE WATEOF. VALUES OF DGF FOR AL3 + (2),HASI0A (6),AL(OH)A (7) , OTHERS (2)? DHF ALANIA- (2),OTHERS (1).

U3 95

SOURCES FOR TABLE 3

(1) Helgeson H. C. (1969) Thermodynamics of hydrothermal systems at elevated temperatures and pressures. Amer. T. Sci. 267, 729-804.

(2) Wagman D. D., Evans W. H., Parker V. E., Halow I., Baily S. M., and Schuimi R. H. (1968) Selected values of chemical ther­ modynamic properties. National Bureau of Standards Technical Note 270-3, 264 pp.

(3) Robie R. A. and Waldbaum D. R. (1968) Thermodynamic properties of minerals and related substances at 298.15°K (25°C) and one atmosphere (1.013 bars) pressure and at higher tem­ peratures. U. S. Geol. Surv. Bull. 1259, 256 pp.

(4) Hostetler P. B. and Christ C. L. (1968) Studies in the system MgO-SiO^-CCL-^O (I): the activity-product constant of chrysotlle. Geochim. Cosmochim. Acta 32, 482-497.

(5) Zen E-An (1972) Gibbs free energy, enthalpy and entropy of ten rock-forming minerals: calculations, discrepancies, implications. Amer. Mineral 57, 524-553.

(6) Tardy Y. and Garrels R. M. (1974) A method of estimating the Gibbs energies of formation of layer silicates. Geochim. Cosmochim. Acta 38, 1101-1116.

(7) Hem T. D. and Roberson C. E. (1967) Form and stability of alu­ mi n u m hydroxide complexes in dilute solution. U. S. Geol. Surv., Water Supply Paper 1827-A, 55 pp.

(8) Bricker 0. P., Nesbitt N. W., and Gunter W. D. (1973) The stability of talc. Amer. Mineral 58, 64-72.

(9) Christ C. L., Hostetler P. B., and Siebert R. M. (1973) Studies in the system MgO-SiC^-CC^-^O (III) : the activity-_ product constant of sepiolite. Amer. T. Sci. 273, 65-83.

(10) Routson R. C. and Kittrick T. A. (1971) Illite solubility. Soil Sci. Soc. Amer. Proc. 35, 714-718. 96

SOURCES FOR TABLE 3 (Continued)

(11) Garrels R. M., M. E. Tharpson, and Siever R. (1961) Control of carbonate solubility by carbonate complexes. Alter. J. Sci. v. 259:24-45.

(12) N a i r V. S. K. and Nancollas G. H. (1958) Thermodynamics of ion association Part IV. Magnesium and zinc sulfates. J. Chem. See. (London): 3706-3710.

(13) Bell R. P. and George J. H. B. (1953) The incomplete dissocia­ tion of seme thallous and calcium salts at different temperatures. Faraday Soc. Trans, v. 49 (6):619-627.

(14) Jenkins I. L. and Monk C. B. (1950) The conductances of sodium, potassium, and lanthanum sulfates at 25°. J. Amer. Chem. Soc. v. 72:2695-2698.

(15) Garrels R. M. and Tharpson M. E. (1962) A chemical model for sea water at 25°C and one atmosphere total pressure. Auer. J. Sci. v. 260:57-66. STATION DATE DEPTH TEMP C CA 2 + MG 2+ NA ♦ K ♦ AL 3 + 1926 5-02-75 1 9.9 0 9. 90 197.90 3250. 00 161.0*3 .0 3 1926 7-09-75 1 22.50 12. 50 161.00 3200. 00 153.00 . G5 19 2 6 9-02-75 1 2 1 .go 11. 50 126.00 292C. 00 196.00 .02 11-03-75 1 1 3 . d 0 11.00 127.00 3090. 00 1 7 5 .OP .02 01-07-76 01. 6.00 11. 00 125.00 3090. 00 162.0 -0 1926 3-17-76 1 2 0.50 11. 00 139.00 3050. 00 170.00 -0 19 2 6 6-02-76 1 18.50 10.23 130.00 3060. 00 162.00 -0 1927 5-02-75 5 8.20 10. 50 192.00 3300. 00 167.00 .03 1927 7-09-75 5 19.90 1 C . 6 0 157.00 3130. 00 199 *. 00 .06 1927 9-02-75 5 20.53 11.30 129.00 3020. 00 196 • 0u -0 11-03-75 5 13.2 5 1G. 90 127.00 3160. 00 165.00 .02 01-07-76 05. 6.0 0 10.70 122.00 3060. 00 191.00 -0 1927 3-17-76 5 21.00 10.90 136.00 3030. 00 160.00 -0 1927 6-02-76 5 16.50 10.92 131.00 3 0 9 C • 00 166 . DC - 0 1923 5-02-75 iu 8.01 10.90 195.50 3270. 00 165.0 0 .05 1923 7-09-75 10 16.00 11. 50 155.00 3230. 00 159 . 00 .08 1928 9-02-75 10 20.50 11. 50 129.00 3010. 00 165.00 -0 11-03-75 10 13.20 10.70 123.00 3130. 00 170.00 .05 01-07-76 10 . 6.00 11.2 0 126.00 3060. 0 0 1 6 9 . OC -0 1928 3-17-76 10 21.00 10.30 135.00 3030. 00 160.00 -0 1926 6-02-76 10 15.50 ' 19.22 131.00 3090. 00 166.00 -0 1930 5-02-75 20 7.50 9.90 197.30 3200. 00 173.00 .02 193 0 7-09-75 20 11.25 11. CO 166.00 3366. 00 156.00 .05 193 3 9-0 2-75 20 11.50 11.30 131.00 3060. 00 167.00 -0 11-03-75 20 13.20 11. 50 127.00 3160. 00 170.00 .01 01-07-76 20. 6.0 0 11.10 132.00 3030. 00 157.00 -0 1930 3-17-76 20 2 0.80 11.7 0 136.00 3070. 00 170.00 - 0 1930 6-0 2-76 20 9.5 !. 10.39 127.00 3060. 00 169.0 - 0 1931 5-02-75 25 6.0 0 8.70 138.50 3280. 00 163.00 .02 1931 7-09-75 25 9.50 11.50 161.00 3350. 00 156.00 . 06 1931 9-02-75 25 9.5 0 10 . 30 127.00 2990. 00 165.00 ~C 11-03-75 32 4. 30 10.70 129.00 3200. no 177.0. .02 01-07-76 28. 6.0 0 11. 00 129.00 3030. 00 239.00 -0 1932 3-17-76 26 20.50 11. 00 136.00 3060. 00 163.00 -0 1932 1 6-02-76 30 8.00 1 0 .39 131.00 3090. 00 163.00 -0

APPENDIX TABLE 4. CHEMI9AL ANALYSES FROM HA LAKE. (CONTINUED)

U3 STATION DATE DEPTH PH CL - S04 2- HC03 - SI 02 P04 3- 1426 5-02-75 1 9.35 2279.00 2051.00 288 8. 00 . 60 1.66 1426 7-09-75 1 9.40 2230.00 1998.00 2675.00 .08 1. 53 1426 9-02-75 1 9.42 2322.00 1693.00 2833.00 -0 1. 55 ii-G 3-75 1 9.46 2293. 00 2076.00 2867.00 1.10 1.57 01-07-76 01. 9.70 2340.00 1996.00 2769.00 .90 1.77 1426 3-17-76 1 9.0 0 2173.00 2072.00 3000.GO .50 1. 60 1426 6-02-76 1 9.39 2334.00 2080.00 2939.00 1.20 1. 37 1427 5-02-75 5 9.32 2286.00 2136.00 2896.00 1.00 1.47 1427 7-0 9-75 5 9.45 2222. 00 2003.00 2 664.00 . 09 1.59 1427 9-02-75 5 9.41 2224.00 1985.00 2658.00 .42 1. 56 11-03” 7 5 5 9.4 3 2260.CO 2043.00 2 848.00 1.10 1.60 .01-07-76 05. 9.65 2260.CO 2073.00 2769.00 . 7U 1. 60 1427 3-17-76 5 9.3 0 2157.0 0 2016.00 2985.00 .40 1.77 1427 6-02-76 5 9.49 2275.00 2132.00 2951.00 1.10 1.53 1428 5-02-75 10 9.3 0 2264. 00 2111.00 2897.00 .70 1.75 14 2 8 7-09-75 10 9.45 2225. 00 1984.00 2657.00 .06 1.44 1426 9-02-75 10 9.40 2214.0(1 1972.00 2634.00 . 32 i . 49 11-0 3-75 10 9.43 2276.00 2156.00 2862.00 1.30 1.70 01-07-76 10. 10.05 2276.00 2061.00 2772. 00 .80 1. 67 1428 3-17-76 10 9.31 2157.00 20 00 . 0 0 2980.CO .50 1.66 1428 6-02-76 10 9.46 2240.00 19 o 4 • 0 0 2931. 00 .80 1. 65 1431 5-02-75 20 9.34 230 4. CO 2074.00 2897. 00 . 80 1.47 1430 7-09-75 20 9.45 2269.00 2026.00 2710.00 . 75 1.90 1430 9-02-75 20 9.41 2315.00 1967.00 2823.00 -0 1.15 11-03-75 20 9.45 2227. 00 2223.00 2857. 00 .90 1. 65 01-07-76 20. 9.95 2276.00 20 5 7.00 2769.00 . 80 1.61 1430 3-17-76 20 9.28 2173.00 2005.00 2976.00 .60 1.83 1430 6-02-76 20 9.5 0 2240.CO 2226.00 2909.on 1.10 1. 59 1431 5-02-75 25 9.3 0 2279.0 0 2149.0 0 2395.00 1.00 1.78 1431 7-09-75 25 9.40 2275.00 20 64.00 2712. 00 . 0 8 1.96 1431 9-02-75 25 9.33 2289.00 2031.00 2823. 00 . 35 1.12 11-03-75 32 9.25 2293.00 2237.00 2869.00 1.90 1.44 01-07-76 26. 9.75 2308.00 2104.00 2769.00 1.00 1.77 1432 • 3-17-76 26 9.26 2173. 00 19 77.00 2976.00 .60 1. 77 1432 6-0 2-76 30 9.4 8 2256.CO 20 30.0 0 2907.00 1.30 1.84

APPENDIX TABLE 4. CHEMICAL ANALYSES FROM WALKER LAKE.