The nature of faults and hydrothermal veins in corehole SB-15-D, The Geysers Steam Field, California
- Univ. of Utah, Salt Lake City, UT (United States)
Porosity in The Geysers Coring Project corehole SB-15-D is concentrated along vuggy, steeply-dipping, hydrothermal calcite-quartz {plus_minus} adularia veins. There is little difference in the texture and abundance of these veins between the upper two thirds of the core, interpreted as caprock, and the lower two-thirds, in which two, vein-controlled, fluid-loss zones (probable steam entries) were encountered. However, vugs in the caprock veins are locally choked with mixed-layer clay, whereas those in the deeper steam-reservoir veins generally lack this clay but contain calc-silicate minerals. Steeply-dipping, concordant faults concentrated in argillite throughout the core show predominantly strike-slip displacement. Although movement was predominantly along argillites, the lithology appears to have deformed in a ductile manner, and porosity development was minimal. High-angle dilational fractures were developed contemporaneously in the graywackes. These fractures in the graywacke were only partially filled by secondary minerals, and are potential steam conduits in the vapor-dominated geothermal system.
- DOE Contract Number:
- AC07-95ID13274
- OSTI ID:
- 175622
- Report Number(s):
- CONF-951037-; TRN: 95:008065-0033
- Resource Relation:
- Conference: Annual meeting of the Geothermal Resources Council, Reno, NV (United States), 8-11 Oct 1995; Other Information: PBD: 1995; Related Information: Is Part Of Accomplishments of the past and challenges of the future. Transactions, Volume 19; PB: 604 p.
- Country of Publication:
- United States
- Language:
- English
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