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University of Nevada Reno SILICATE and CARBONATE SEDIMENT 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
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