Integrated Alteration Mineralogy and Fluid-Inclusion Study at the Dixie Valley Geothermal Field, Nevada

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Conference Paper: Integrated Alteration Mineralogy and Fluid-Inclusion Study at the Dixie Valley Geothermal Field, Nevada

Abstract

Cuttings from geothermal wells in Dixie Valley, Nevada document the complex history of the Jurassic reservoir rocks now contained within the hanging wall of the Stillwater normal fault. Six stages of post- Oligocene alteration can be recognized on the basis of mineral paragenesis, rock associations, fluid-inclusion temperatures and apparent salinities. The paragenetic sequence from oldest to youngest consists of: Stage I) epidote-chlorite-calcite veins; Stage 11) illite; Stage 111) wairakite-quartz-calcite-potassium feldspar-epidote veins; Stage IV) mixed-layer illitesmectite and quartz-calcite veins; Stage V) chalcedonic quartz-dolomite-calcite-chlorite/smectitebarite- hematite veins; and Stage VI) quartz-calcite veins. Fluid-inclusion data yield the following temperatures and apparent salinities in weight percent NaCl equivalent: Stage I) 270" to 325°C and 1.4 to 1.6%; Stage 11) 220" to 270°C and 1.6 to 1.9%; Stage 111) 230" to 240°C and 1.2%; Stage IV) 180" to 220°C and 0.4 to 0.5%; Stage V) <160"C and 0.0%; and Stage VI) 200" to 270°C and 0.0 to 0.5%. Presentday fluid inclusions deposited in wellbore scale yield homogenization temperatures of about 200°C and salinities of 0.0 to 0.4 weight percent NaCl equivalent. Moderately saline fluids of the Stage I through 111 assemblages appear to be associated with hydrothermal systems that developed during initial Basin and Range extension. Low salinity and low temperature Stage JV and V inclusions suggest the presence of cool fluids at shallow depths along the Stillwater fault. Stage VI quartz and calcite veins were deposited by the modern geothermal system (Tmax = 248"C, salinity = 0.1-0.2 wt %) along this

still-active fault.

Authors 
Susan Juch Lutz and Joseph N. Moore






Conference 
Twenty-Third Workshop on Geothermal Reservoir Engineering; Stanford, California; 1998/06/01


Published 
Stanford University, 1998





DOI 
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Online 
Internet link for Integrated Alteration Mineralogy and Fluid-Inclusion Study at the Dixie Valley Geothermal Field, Nevada

Citation

Susan Juch Lutz, Joseph N. Moore. 1998. Integrated Alteration Mineralogy and Fluid-Inclusion Study at the Dixie Valley Geothermal Field, Nevada. In: Proceedings. Twenty-Third Workshop on Geothermal Reservoir Engineering; 1998/06/01; Stanford, California. Stanford, California: Stanford University; p. unknown


Related Geothermal Exploration Activities
Activities (1)


Areas (1)
  1. Dixie Valley Geothermal Area
Regions (0)