Recharge of Geothermal Fluids in the Great Basin

Abstract

In August 1988, the Division of Earth Sciences, University of Nevada Las Vegas, began an investigation of geothermal fluid genesis in the Great Basin, Western United States. Currently, the are two theories that attempt to explain the nature and occurrence of geothermal fluids. Both theories rely on interpretation of stable light isotope ratios of geothermal fluids and meteoric waters. The schools of "contemporary recharge" argues that precipitation from elevations in excess of 2,500 meters have stable light isotope ratios that are identical to those of geothermal springs and wells. This group concludes that geothermal resources are recharged by modern, high elevation precipitation. An alternative theory is proposed by the school of "palo fluid recharge". This theory is based, in part, on pioneering paleo climate studies by Dansgaard et al. (1969) who, using continuous core form the Greenland Ice Sheet, identified a transition from modern, isotopically enriched meteoric water to paleo isotopically depleted water between 12,000 and 8,000 years BP. The purpose of this paper is to describe the elements of an investigation that is designed to assess the geologic and temporal fracemwork required to support the hypothesis of paleo fluid recharge of geothermal fluids. The investigation relies on interpretation of chemical and isotopic data from geothermal fluids, meteoric waters, and paleo climate proxies such as glacial ice core and packrat midden studies. Interpretations are based on regional and systematic variations of stable light isotopes within the Great Basin.