Preliminary Ranking of Geothermal Potential in the Cascade and Aleutian Volcanic Arcs, Part Ⅰ: Data Collection

摘要

As part of a DOE funded project on Geothermal Play Fairway Analysis, a geothermal assessment of volcanic centers in the Cascade and Aleutian volcanic arcs is being conducted that includes a large data gathering effort discussed in this paper, and a statistical modeling effort to qualitatively rank the geothermal potential of individual VCs in these two US arcs, discussed in a second companion paper. The data compiled from the Cascades and Aleutians are compared to geologic, geochemical and geophysical information from productive volcanic arc centers in the other parts of the world. Seven other volcanic arc segments from around the globe are used in this comparative study. Preliminary findings from data evaluation indicate that there are systematic changes in structural setting, from an extensional influence south of Mt. Hood (in part due to encroachment of the back arc in the southern half) to more compressional north of Mt. Hood. Comparison with productive geothermal fields around the world shows that large fumarolic areas are associated with most ＞240°C power-producing geothermal systems outside the US arcs (e.g., Kamojang, Indonesia, among others), whereas there is a general absence of large fumarolic areas in the Cascades and Aleutian arcs, aside from of the Lassen volcano area. As a result, fewer deep, successful wells have been drilled in the US in the Cascades and Aleutians, whereas there are many producing wells associated with fumarolic volcanic centers outside the US. Few high temperature (＞200°C) systems are known in the US arcs (e.g., Newberry), and there is no direct evidence to date for very high temperature (＞300°C) geothermal systems, whereas there are 21 such known systems in other volcanic arcs of the world (e.g., Silangkitang and Lahendong, Indonesia; Hachijojima and Matsukawa, Japan; Amiata, Italy; Los Azufres, Mexico, to name a few).