Evaluation of Deep Geothermal Resources Using Rare Earth Elements, Snake River Plain, Idaho, USA

Abstract

In a 2008 resource assessment of the western United States, the U.S. Geological Survey (USGS) estimated that there is over 30 GWe of electric power potential for undiscovered conventional geothermal systems. Over ten Known Geothermal Resource Areas (KGRAs) were previously identified by the USGS over large portions of eastern Oregon and southern Idaho, but very little geothermal development has occurred in this region over the past 30 years. We hypothesize that within some of these KGRAs, large under-characterized prospective geothermal prospects exist with significant elevated heat flow that are representative of commercial grade resources. The objective of this project is to provide a fresh look at these systems using modern exploration tools and techniques to identify and characterize geothermal prospects and highlight areas that warrant further exploration. The Snake River Plain (SRP) in southeastern Idaho is an area of high heat flow with significant potential geothermal resources. However, rapid groundwater flow in high permeability surficial basalts effectively masks thermal signatures of deep-seated geothermal systems in the SRP. To identify potential signatures of hidden geothermal systems, we have measured chemical and isotopic compositions of thermal fluids from across the region sampled from hot springs and thermal wells. Here we report the rare earth element (REEs) data collected from more than 150 geothermal springs and wells within and along the margins of the Snake River Plain. This REE dataset provides a valuable window into the geothermal conditions that exist deep in the SRP Additionally, the REE data provide important insights into the geochemical changes that occur as geothermal water migrates from deep in the SRP to the springs and wells along margin of the SRP.