Quaternary volcanism in the Salton Sea geothermal field, Imperial Valley, California

Journal Article · Mon Mar 01 00:00:00 EST 1976 · Geol. Soc. Am., Bull.; (United States)

DOI:https://doi.org/10.1130/0016-7606(1976)87<347:QVITSS>2.0.CO;2· OSTI ID:7196173

Robinson, P T ^[1]; Elders, W A; Muffler, L J.P.

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1. Univ. of California, Riverside

The Salton Sea geothermal field lies in the Salton Trough, the landward extension of the Gulf of California, an area of active crustal spreading. Surface volcanic rocks of the field consist of five small rhyolite domes extruded onto Quaternary sediments of the Colorado River delta. Two domes are linked by subaqueous pyroclastic deposits; the others are single extrusions with or without marginal lava flows. The domes are low-calcium, alkali rhyolite with 1 to 2 percent crystals. Similar silicic rocks found in wells have been extensively altered by geothermal brines. Basaltic rocks occur as xenoliths in the domes and as subsurface dikes, sills, or flows. The xenoliths consist of low-potassium tholeiitic basalt similar to that of the East Pacific Rise. Subsurface basaltic rocks are mineralogically similar to the xenoliths but have undergone extensive hydrothermal alteration. Numerous partly melted granitic xenoliths in the domes show various degrees of either cotectic melting along quartz-feldspar grain boundaries or disequilibrium incongruent melting of hydrous ferromagnesian minerals. These rocks are sodic granite containing notably higher SiO/sub 2/, CaO, and Na/sub 2/O and lower total iron than the enclosing rhyolite. Compositions and textures suggest that the granite xenoliths are fragments of basement rather than the crystallized equivalents of the rhyolite magma. The bimodal basalt-rhyolite assemblage of the Salton Sea geothermal field is believed to have formed by partial fusion in two stages of mantle peridotite, forming successive rhyolitic and basaltic melts. After formation, the rhyolitic magma was partly contaminated by continental crust material.

• OSTI ID: 7196173
• Journal Information: Geol. Soc. Am., Bull.; (United States), Vol. 87:3
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
SALTON SEA GEOTHERMAL FIELD
VOLCANIC ROCKS
VOLCANISM
BASALT
CALIFORNIA
CHEMICAL COMPOSITION
GRANITES
IGNEOUS ROCKS
IMPERIAL VALLEY
INCLUSIONS
MAGMA
PETROLOGY
RHYOLITES
TABLES
GEOLOGY
GEOTHERMAL FIELDS
INFORMATION
NORTH AMERICA
ROCKS
USA
WESTERN REGION
150201* - Geology &amp; Hydrology of Geothermal Systems- USA- (-1989)