Geochemistry of thermal/mineral waters in the Clear Lake region, California, and implications for hot dry rock geothermal development

Technical Report · Mon Feb 01 04:00:00 EST 1993

DOI:https://doi.org/10.2172/7090069· OSTI ID:7090069

Goff, F; Adams, A I; Trujillo, P E; Counce, D; Mansfield, J

Thermal/mineral waters of the Clear Lake region are broadly classified as thermal meteoric and connote types based on chemical and isotopic criteria. Ratios of conservative components such as B/Cl are extremely different among all thermal/mineral waters of the Clear Lake region except for clusters of waters emerging from specific areas such as the Wilbur Springs district and the Agricultural Park area south of Mt. Konocti. In contrast, ratios of conservative components in large, homogeneous geothermal reservoirs are constant. Stable isotope values of Clear Lake region waters show a mixing trend between thermal meteoric and connote end-members. The latter end-member has enriched [delta]D as well as enriched d[sup l8]O, very different from typical high-temperature geothermal reservoir waters. Tritium data and modeling of ages indicate most Clear Lake region waters are 500 to > 10,000 yr., although mixing of old and young components is implied by the data. The age of end-member connate water is probably > 10,000 yr. Subsurface equilibration temperature of most thermal/mineral waters of the Clear Lake region is [le] 150[degrees]C based on chemical geothermometers but it is recognized that Clear Lake region waters are not typical geothermal fluids and that they violate rules of application of many geothermometers. The combined data indicate that no large geothermal reservoir underlies the Clear Lake region and that small localized reservoirs have equilibration temperatures [le] 150[degrees]C (except for Sulphur Bank Mine). Hot dry rock technologies are the best way to commercially exploit the known high temperatures existing beneath the Clear Lake region, particularly within the main Clear Lake volcanic field.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: CAEC; California Energy Resources Conservation and Development Commission, Sacramento, CA (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 7090069
• Report Number(s): LA-12510-HDR; ON: DE93007458
• Country of Publication: United States
• Language: English

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