The heating duration and provenance age of rocks in the Salton Sea geothermal field, southern California

摘要: Abstract 40Ar/39Ar step heating of single K-feldspar crystals (∼ 500 μg) in a furnace with low argon blank and accurate temperature control provide constraints on the thermal history Salton Sea geothermal field, southern California. Estimates 40Ar loss from detrital K-feldspars, coupled kinetic information gleaned laboratory degassing 39Ar, allow possible histories to be evaluated. Samples core cuttings sandstones State 2–14, Landers #1, Dearborn Farms Magmamax #2, Elmore #3 Sinclair wells have been analyzed for this purpose. No recent 40Ar∗ is recognized any 17 measured, even samples currently at temperatures greater than 275°C. This observation suggests that present distributions these not maintained 1000 years. However, aggregates 100 mg) two do reveal 2–14 well, suggesting time scale 5000 years near-peak conditions. These estimates duration are broadly consistent earlier results modelling, but support interpretations paleotemperatures were once hotter present. Provenance ages span Tertiary through Middle Proterozoic cluster 25, 70 1250 Ma. age peaks very common K-Ar detachment terranes southeastern California southwestern Arizona, both drained by Colorado River. coincidence supports suggestions sands Trough derived mainly Unrealistically apparent activation energies (