Geothermal Resource Definition at Mt. Spurr, Alaska

Abstract

The active, Aleutian-arc stratovolcano Mt. Spurr and its flank-cone, Crater Peak, are the target of current geothermal exploration in the western Cook Inlet. Lying just 80 miles west of Anchorage, AK, the Mt. Spurr complex serves as both a source of hazard and of potential energy. Recent eruptive episodes (’53 and ’92) make development here challenging – but the young nature of the volcanic system (all less than ~255ka), extensive, active faulting, advanced surface alteration suites and fluid chemistries consistent with a geothermal reservoir, also make Mt. Spurr very prospective. Field reconnaissance during the summer of 2009 (including mapping and surface geochemical sampling) set the stage for a full-scale exploration program in the summer of 2010. High resolution satellite imagery coupled with LiDAR kicked-off the exploration program, providing base maps (especially structure) of this poorly known edifice. Heli-bourne aeromagnetics and an aggressive ground-based geophysical suite of gravity and MT were completed over several months. The synthesis of these datasets with additional geologic mapping, geochemical sampling and two ~1000’ core holes have produced a working geothermal exploration model and served to elucidate large scale structural controls on this young volcanic edifice. Both deep and shallow features were identified in the geophysics and airborne LiDAR, including large scale conductors coincident with surface hydrothermal fluid flow, de-magnetized regions coincident with LiDAR-delineated surface volcanic features and major and minor fault structures coincident with known regional structural trends. We plan to target these major structures (where coincident with geophysical anomalies) with additional intermediate depth core holes in the summer of 2011, the goal of which is to define a viable geothermal reservoir (temperature, fluid and permeability).