Metamorphosed Plio-Pleistocene evaporites and the origins of hypersaline brines in the Salton Sea geothermal system, California: Fluid inclusion evidence
- Univ. of California, Riverside (USA)
The Salton Sea geothermal system (SSGS) occurs in Plio-Pleistocene deltaic-lacustrine-evaporite sediments deposited in the Salton Trough, an active continental rift zone. Temperatures up to 365{degree}C and hypersaline brines with up to 26 wt.% TDS are encountered at 1-3 km depth in the sediments, which are undergoing active greenschist facies hydrothermal metamorphism. Previous models for the origins of the Na-Ca-K-Cl brines have assumed that the high salinities were derived mainly from the downward percolation of cold, dense brines formed by low-temperature dissolution of shallow non-marine evaporites. New drillcores from the central part of the geothermal field contain metamorphosed, bedded evaporites at 1 km depth consisting largely of hornfelsic anhydrite interbedded with anhydrite-cemented solution-collapse shale breccias. Fluid inclusions trapped within the bedded and breccia-cementing anhydrite homogenize at 300{degree}C and contain saline Na-Ca-K-Cl brines. Some of the inclusions contain up to 50 vol.% halite, sylvite and carbonate crystals at room temperature, and some halite crystals persist to above 300{degree}C upon laboratory heating. The data are consistent with the trapping of halite-saturated Na-Ca-K-Cl fluids during hydrothermal metamorphism of the evaporites and accompanying solution collapse of interbedded shales. The authors conclude that many of the slat crystals in inclusions are the residuum of bedded evaporitic salt that was dissolved during metamorphism by heated connate fluids.
- DOE Contract Number:
- FG03-85ER13408
- OSTI ID:
- 5327557
- Report Number(s):
- CONF-8701162-; CODEN: GCACA
- Journal Information:
- Geochimica et Cosmochimica Acta; (USA), Vol. 52:5; Conference: American conference on research on fluid inclusions (ACROFI), Socorro, NM (USA), 5 Jan 1987; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
ANHYDRITE
INCLUSIONS
BRINES
FLOW MODELS
CHEMICAL COMPOSITION
SALTON SEA GEOTHERMAL FIELD
ROCK-FLUID INTERACTIONS
CALIFORNIA
DISSOLUTION
DRILL CORES
EVAPORITES
FLUID FLOW
GEOCHEMISTRY
HALITE
HYDROTHERMAL ALTERATION
HYDROTHERMAL SYSTEMS
METAMORPHISM
PLEISTOCENE EPOCH
PLIOCENE EPOCH
RIFT ZONES
SALINITY
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM SULFATES
CENOZOIC ERA
CHEMISTRY
ENERGY SYSTEMS
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGIC STRUCTURES
GEOTHERMAL FIELDS
GEOTHERMAL SYSTEMS
HALIDE MINERALS
MATHEMATICAL MODELS
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
QUATERNARY PERIOD
ROCKS
SEDIMENTARY ROCKS
SULFATE MINERALS
SULFATES
SULFUR COMPOUNDS
TERTIARY PERIOD
USA
152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions
580000 - Geosciences