Metamorphosed Plio-Pleistocene evaporites and the origins of hypersaline brines in the Salton Sea geothermal system, California: Fluid inclusion evidence

Conference · Sun May 01 04:00:00 EDT 1988 · Geochimica et Cosmochimica Acta; (USA)

OSTI ID:5327557

McKibben, M A; Williams, A E; Okubo, Susumu ^[1]

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1. 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--
• Conference Information: Journal Name: Geochimica et Cosmochimica Acta; (USA) Journal Volume: 52:5
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152003* -- Geothermal Data & Theory-- Rock-Water-Gas Interactions
58 GEOSCIENCES
580000 -- Geosciences
ALKALINE EARTH METAL COMPOUNDS
ANHYDRITE
BRINES
CALCIUM COMPOUNDS
CALCIUM SULFATES
CALIFORNIA
CENOZOIC ERA
CHEMICAL COMPOSITION
CHEMISTRY
DISSOLUTION
DRILL CORES
ENERGY SYSTEMS
EVAPORITES
FEDERAL REGION IX
FLOW MODELS
FLUID FLOW
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC STRUCTURES
GEOTHERMAL FIELDS
GEOTHERMAL SYSTEMS
HALIDE MINERALS
HALITE
HYDROTHERMAL ALTERATION
HYDROTHERMAL SYSTEMS
INCLUSIONS
MATHEMATICAL MODELS
METAMORPHISM
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PLEISTOCENE EPOCH
PLIOCENE EPOCH
QUATERNARY PERIOD
RIFT ZONES
ROCK-FLUID INTERACTIONS
ROCKS
SALINITY
SALTON SEA GEOTHERMAL FIELD
SEDIMENTARY ROCKS
SULFATE MINERALS
SULFATES
SULFUR COMPOUNDS
TERTIARY PERIOD
USA