Thermal Modeling and EGS Potential of Newberry Volcano, Central Oregon

Abstract

Newberry Volcano, located in central Oregon in the Deschutes National Forest, is a large bimodal Quaternary volcanic edifice that covers 1600 km2. Various periods of geothermal exploration in and around the volcano over the last 30+ years has resulted in a robust dataset of wellbore temperatures, cores, gravity data, and other geophysical surveys. Wells drilled on the flanks of Newberry have an average geothermal gradient of 130°C/km and show a roughly circular heat flow anomaly centered on the caldera. Geologic data suggest a typical interval of ~200,000 years between large caldera forming eruptions. Using these data along with new industry collected gravity data and recent tomographic studies; a 2-D finite-difference heat conduction program was used to model the heat source under the volcano. The available temperature data on the west flank of the volcano can be explained by silicic sill intrusions recurring at a 200,000 year rate over the 500,000 year lifetime of the volcano.