Fluid Geochemistry of the Surprise Valley Geothermal System

Abstract

Despite the prevalence of hot springs and the drilling of several test wells, the Surprise Valley geothermal system remains relatively undeveloped. One reason for this is that the source and flow-path of recharge waters within the subsurface remains enigmatic. Our study aims to determine this through a comprehensive investigation of the geochemistry of the Surprise Valley fluids. Our approach divides the valley into five regions that we believe to be operationally distinctive in their channeling and mixing of waters. We compiled and analyzed relationships between all of the available major element and isotopic geochemical data on thermal waters from within these regions. Chemical data was modeled Geochemists Workbench®. Initial results support the theory that discrete recharge sources and mechanisms are operating throughout the valley. Our geochemical modeling suggests that the hottest waters within the system originate at around 170° C, and may be diluted by cold waters from multiple sources. We believe this study may be useful in the context of emergent geophysical work that is investigating structures controlling fluid flow within the valley.