Buried rhyolites within the active, high-temperature Salton Sea geothermal system

摘要: Abstract Previously unrecognized pulses of rhyolite volcanism occurred in the Salton Trough between 420 ± 8 ka and 479 ± 38 ka (2σ), based on high-spatial resolution U–Pb zircon geochronology. Presently, these lavas, tuffs shallow subvolcanic sills are buried to depths ~ 1.6 2.7 km at ambient temperatures 200 300 °C, overprinted by propylitic potassic hydrothermal alteration mineral assemblages consisting finely intergrown quartz, K-feldspar, chlorite, epidote, minor pyrite. Alteration resistant geochemical indicators (whole-rock Nd-isotopes, oxygen-isotopes) reveal that rhyolites derived from remelting MORB-type crust was chilled hydrothermally altered deep-circulating waters. dating confirms presence Bishop Tuff well State 2-14 ~ 1.7 km depth, approximately 5 km NE geothermal wells penetrated rhyolites. These results indicate accelerated subsidence towards center Trough, increasing 2.2 mm/a 3.8 mm/a. Based results, present-day Sea field is identified as a focus zone episodic rhyolitic volcanism, intense heat flow metamorphism predates activity Holocene least ~ 400 ka.