Heat flow determinations and implied thermal regime of the Coso geothermal area, California

Conference · Wed Dec 01 00:00:00 EST 1976 · EOS, Trans., Am. Geophys. Union; (United States)

OSTI ID:5414667

Combs, J

Obvious surface manifestations of an anomalous concentration of geothermal energy at the Coso Geothermal Area, California, include fumarolic activity, active hot springs, and associated hydrothermally altered rocks. Abundant Pleistocene volcanic rocks, including a cluster of thirty-seven rhyolite domes, occupy a north-trending structural and topographic ridge near the center of an oval-shaped zone of late Cenozoic ring faulting. In an investigation of the thermal regime of the geothermal area, temperatures have been obtained to depths up to 133 m in 22 boreholes with measurements being made at least four times in each borehole. Geothermal gradients ranged from 24/sup 0/C/km to 450/sup 0/C/km. The high gradients arise from convecting hot water and magma which are cooled at shallow depth by conduction of heat to the surface. Thermal conductivity measurements ranging from 3.2 to 10.5 mcal/cm-sec-/sup 0/C were made on both cores and drill cuttings. The resultant heat flow values of 2.5 to 18 HFU are typical of geothermal areas. The actual process by which heat is transferred is rather complex; however, the heat flow determinations can be divided into two groups. The first group, less than 6.5 HFU, are indicative of regions with primarily conductive regimes although deep-seated mass transfer is implied. The second group, greater than 6.5 HFU, are characteristic of regions with considerable convective heat transfer in the shallow subsurface. The high heat flow values are essentially restricted to the central rhyolite dome field and the associated surface thermal manifestations. Heat transferred by convection of water would be rapidly exhausted if it were not intermittently supplied with energy from depth; therefore, the heat flow data substantiate the concept that the ring structure and associated volcanic rocks are products of a large magma chamber that has periodically erupted lava during the past one million years.

• Research Organization: Univ. of Texas, Dallas
• OSTI ID: 5414667
• Journal Information: EOS, Trans., Am. Geophys. Union; (United States), Vol. 57:12; Conference: AGU fall annual meeting, San Francisco, CA, USA, 6 Dec 1976
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
CALIFORNIA
GEOTHERMAL FIELDS
HEAT FLOW
BOREHOLES
FUMAROLES
GEOLOGIC FAULTS
GEOTHERMAL GRADIENTS
HOT SPRINGS
KGRA
MAGMA
MASS TRANSFER
VOLCANIC ROCKS
CAVITIES
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
NORTH AMERICA
ROCKS
TEMPERATURE GRADIENTS
THERMAL SPRINGS
USA
150301* - Geothermal Exploration & Exploration Technology- Geophysical Techniques & Surveys