Hydrothermal Alteration Minerals of the Geysers Steam Field, California and their Potential Use in Exploration
Little information has been published on the hydrothermal alteration minerals occurring at depth in the Geysers steam field, California. Steiner (1958) reported the occurrence of wairakite from a well; McNitt (1964) identified pyrite, sericite, calcite, quartz, siderite, apatite and chlorite in cores of Franciscan graywacke and greenstone. Recently, Union Oil Geothermal Division furnished a set of well cores from the cap rock overlying the steam reservoir for geophysical studies (Lockner -e t -a l . , 1980). Cores of metagraywacke and greenstone from 4 wells were compared to unaltered Franciscan metagraywacke from surface exposures. Several previously unreported alteration minerals were found in the cored rocks, including epidote, tremolite-actinolite, prehnite and tourmaline. This note describes the observed alteration minerals and some of the factors that controlled their growth.
- Research Organization:
- U.S. Geological Survey, Menlo Park, CA
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AT03-80SF11459
- OSTI ID:
- 889284
- Report Number(s):
- SGP-TR-50-49
- Resource Relation:
- Conference: Proceedings, Sixth Workshop Geothermal Reservoir Engineering, Stanford University, Stanford, California, December 16-18, 1980
- Country of Publication:
- United States
- Language:
- English
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