GEOTHERMAL POTENTIAL OF THE CASCADE AND ALEUTIAN ARCS BASED ON COMPARISON WITH OTHER PRODUCTIVE ARC SETTINGS AROUND THE WORLD

Ironically, although the US leads the world in geothermal power production, neither the Cascade nor Aleutian arcs currently support electricity production, even though outside the US much of the world’s geothermal power comes from active arc settings. Geopolitical issues have hindered or precluded development in parts of the Cascades (e.g. Medicine Lake, Mt. Lassen), and development in the Aleutians is complicated by remoteness and market access. As such, several decades of geothermal exploration have not achieved power production. Is this lack of success related to the complexity of finding hidden geothermal resources along with legal and economic issues, or is there something fundamental about the geologic and plate tectonic settings that make economic geothermal systems less likely to form? After all, not all volcanoes are created equal in terms of geothermal potential. Characteristics such as presence of rifting, host rock composition, magma composition, and the frequency and youthfulness of volcanism factor into potential viability.

A new research project established with the US Department of Energy seeks to answer these questions to assess geothermal power potential at volcanic centers throughout the Cascade and Aleutian arcs. Because of the lack of current electricity production in US arc settings, the studies necessary for assessing probabilities will come from more thoroughly developed arcs outside North America. A variety of statistical methods will be used to evaluate inter-relationships and correlations with economic geothermal reservoirs of a number of factors, including but not limited to, 1) structural setting (extensional, transtensional, compressive), 2) reservoir host rock characteristics, 3) position of the volcanic center in the arc (along strike and relative to fore-arc vs. back-arc), 4) subduction rate, 4) subduction incidence angle (oblique vs. direct), 5) presence of offsets to the arc trend, 6) youthfulness and eruption frequency, 7) magma composition, 8) presence of caps and degree of dissection, 9) presence of thermal features (fumaroles, hot springs), and 10) fluid chemistry. The resulting statistical relationships and correlations will be used to estimate probabilities and build fairway play exploration models similar to those utilized in petroleum exploration.