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The Geothermal Hydrology of Southern Grass Valley, Pershing County, Nevada

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The Geothermal Hydrology of Southern Grass Valley, Pershing County, Nevada The Geothermal Hydrology of Southern Grass Valley, Pershing County, Nevada By F.H. Olmsted, Alan H. Welch, M.L. Sorey, and D.H. Schaefer U.S. GEOLOGICAL SURVEY Water Resources Investigations Report 96-4139 Menlo Park, California 1997 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY GORDON P. EATON, Director For additional information Copies of this report can be write to: purchased from: F.H. Olmsted U.S. Geological Survey U.S. Geological Survey Branch of Information Services 345 Middlefield Rd., MS 439 Box 25286 Menlo Park, CA 94025 Denver, Colorado 80225-0286 CONTENTS ABSTRACT ......................................................................... 1 INTRODUCTION .................................................................... 2 Purposes of the Study ............................................................. 2 Previous Work ................................................................... 3 Methodology .................................................................... 6 Acknowledgments ................................................................. 7 GEOLOGY.......................................................:.................. 7 Physical Features ................................................................. 7 Major Rock Groups ............................................................... 8 Paleozoic and Mesozoic Basement ............................................. 8 Cenozoic Valley Fill .......................................................... 8 Physical Properties of Rock Materials ............................................... 13 Structure ....................................................................... 15 Pre-Cenozoic History ....................................................... 15 Cenozoic History .......................................................... 16 Basin and Range Faults ..................................................... 17 Thickness of Valley Fill........................................................... 21 HYDROLOGY ..................................................................... 25 Climate ........................................................................ 25 Surface Water................................................................... 25 Ground Water................................................................... 25 Ground-Water Recharge and Discharge ........................................ 25 Ground-Water Movement in the Valley Fill ..................................... 30 Hydrologic Effects of Basin and Range Faults ................................... 35 Ground Water in the Basement and Consolidated Volcanic Rocks ................... 36 AQUEOUS GEOCHEMISTRY ........................................................ 38 Dissolved Constituents ........................................................... 39 Stable Isotopes of Hydrogen and Oxygen ............................................. 43 Isotopic Composition of Precipitation .......................................... 43 Distinction of Thermal from Nonthermal Ground Water ........................... 45 Isotopic Changes from Precipitation to Ground Water ............................. 45 Sources of Thermal and Nonthermal Ground Waters .............................. 46 Age of Thermal Water ...................................................... 47 Chemical Geothermometry ........................................................ 51 SUBSURFACE TEMPERATURE AND HEAT FLOW ..................................... 56 Temperature Distribution in Valley Fill .............................................. 56 CONTENTS HI Temperature Distribution in Basement............................................... 66 Heat Flow ..................................................................... 67 Heat Budget .............................................................. 67 Modes of Heat Flux ........................................................ 67 Convection ............................................................... 67 Advection ................................................................ 68 Conduction ............................................................... 68 Total Heat flux and Average Heat Flow ......................................... 77 MODELS OF BASIN AND RANGE HYDROTHERMAL SYSTEMS ......................... 78 Fault-Plane Model ............................................................... 79 Computational Model ...................................................... 80 Conduction-Only Solutions .................................................. 81 Fluid-Downflow Cases ..................................................... 82 Fluid-Upflow Cases ........................................................ 84 Fluid Residence Time ...................................................... 85 Lateral-Flow Model ............................................................. 85 Computational Model ...................................................... 86 Solutions with Fluid Flow ................................................... 87 Generalizations and Constraints .................................................... 88 SUMMARY AND CONCLUSIONS .................................................... 89 REFERENCES CITED ............................................................... 92 APPENDIX-INVENTORY OF WELLS AND SPRINGS IN SOUTHERN GRASS VALLEY .... 104 Explanation of Table Al ......................................................... 104 Numbers of Test Wells, Private Wells, and Springs .............................. 104 Names of Wells or Springs ................................................. 104 Location Numbers ........................................................ 104 Latitude and Longitude .................................................... 106 Altitude of Land-Surface Datum ............................................. 106 Height ofMeasuring Point.................................................. 106 Depth of Screen or Cap at Bottom ............................................ 106 Nominal Inside Diameter of Casing .......................................... 106 Type of Completion ....................................................... 107 Geophysical Logs Available ................................................ 107 Other Data Available ...................................................... 107 IV The Geothermal Hydrology of Southern Grass Valley, Pershing County, Nevada FIGURES 1. Index map showing location of southern Grass Valley study area ............................. 3 2. Generalized geologic map of southern Grass Valley area .................................. 10 3. Sketch map of southern Grass Valley showing major structural features ...................... 17 4. Section A-A' across southern Grass Valley ............................................. 18 5. Complete Bouguer gravity anomaly map of southern Grass Valley .......................... 19 6. Map showing thickness of fill in southern Grass Valley ................................... 20 7. Sketch map showing location of orifices at Leach Hot Springs ............................. 28 8. Graph showing discharge from orifices 1-29 at Leach Hot Springs .......................... 29 9. Graph showing estimated annual evaporation from hot-water surfaces as a function of temperature .................................................................. 29 10. Map of southern Grass Valley showing location of wells and springs ....................... 32 11. Map showing configuration of water table in southern Grass Valley ........................ 33 12. Map showing depth to water table and distribution of phreatophytes in southern Grass Valley ... 34 13. Diagram showing general chemical character of thermal and nonthermal water in southern Grass Valley area .............................................................. 41 14. Graph showing saturation index for fluorite versus source temperature ..................... 42 15. Graph showing dissolved lithium and boron versus source temperature ...................... 43 16. Graph showing hydrogen and oxygen composition of thermal and nonthermal waters in the southern Grass Valley area ...................................................... 44 17. Graph showing relation of deuterium composition to altitude for nonthermal springs ........... 48 18. Triangular diagram for evaluating sodium-potassium and potassium-magnesium geothermometer temperatures of selected geothermal waters in northern Nevada ........... 55 19. Map showing heat-budget area and location of test wells used for temperature measurement..... 57 20. Graph showing temperature-depth profiles in selected wells .............................. 58 21. Graph showing temperature-depth profiles in wells penetrating valley fill ............:....... 59 22. Graph showing temperature-depth profiles and generalized log of Aminoil USA 11-36 well ..... 60 23. Map showing estimated temperature at base of valley fill in southern Grass Valley ............ 65 24. Map showing conductive heat flow for shallow depth range in southern Grass Valley .......... 70 25. Map showing conductive heat flow for intermediate depth range in southern Grass Valley ...... 71 26. Map showing conductive heat flow for deep depth range in southern Grass Valley ............. 72 27. Map showing areal geology and near-surface conductive heat flow in the Leach Hot Springs thermal area .................................................................. 73 28. Plots of heat flow versus area for six thermal anomalies ................................. 74 29. Diagram
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