| Title | Isotope Transport and Exchange within the Coso Geothermal System |
|---|---|
| Authors | Person, M. A.; Cohen, D.; Sabin, A. E.; Unruh, J. R.; Gable, C. W.; Zyvoloski, G. A.; Monastero, F. C. |
| Year | 2006 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Coso; Isotope transport, mathematical modeling, Coso geothermarl, hydrogeology |
| Abstract | We are investigating the plumbing of the Coso geothermal system and the nearby Coso Hot Springs using finite element models of single-phase, variable-density fluid flow, conductive- convective heat transfer, fluid-rock isotope exchange, and groundwater residence times. Using detailed seismic reflection data and geologic mapping, we constructed a regional crosssectional model that extends laterally from the Sierra Nevada to Wildhorse Mesa, west of the Argus Range. The base of the model terminates at the brittle-ductile transition zone. A sensitivity study was conducted using the model to explore the interaction between local and mountain front recharge, the effects of spatial variations in heat flow, and the role of permeable faults in controlling fluid circulation patterns. The model is constrained by present day bore hole temperature surveys, fluid inclusion temperatures, fluid-rock isotopic alteration patterns, and hot spring activity. While the results are non-unique, the analysis permits us to bracket the likely ranges of permeabilities and heat flow conditions that are consistent with observed data. Our findings suggest that active faults and seismogenic zones in and around the Coso geothermal area have much higher permeability and reactive surface areas than far field crustal rocks such as those in the Sierra Nevada. The Coso Wash fault zone must extend down to brittle-ductile transition zone depths of about 4 km in order for modeled results to match the observed hot spring activity. |