Preliminary Ranking of Geothermal Potential in the Cascade and Aleutian Volcanic Arcs, Part Ⅱ: Structural-Tectonic Settings of the Volcanic Centers

摘要

As part of a Department of Energy funded project on Geothermal Play Fairway Analysis, this paper discusses the methodology and preliminary results of evaluating local structural and tectonic settings associated with permeability fairways in the Aleutian and Cascade arcs. Specific structural settings coupled with appropriate active strain and complementary stress fields are favorable for both the deep vertical permeability necessary for the roots of hydrothermal systems and the shallow permeability at depths economical for commercial development. Favorable structures include intersections of major faults, pull-aparts along strike-slip faults, step-overs between normal faults, fault terminations of normal or reverse faults, displacement transfer zones, accommodation zones, and dense networks of nascent faults or fault intersections. Some volcanic centers overlap with multiple separate individual or compound structures. Multiple supporting parameters are being collected to help characterize the favorability of these structural settings including strain rates, strain style (.e.g., extensional or compressional), Quaternary fault data, fault orientations, stress data, kinematic linkage of vents, and the degree of certainty for the principle parameters. These data will be combined with other data sets such as geochemistry, presence of active geothermal features, characteristics of magmatism and volcanism, and degree of exploration to produce overarching favorability analysis of the Cascade and Aleutian arcs as discussed in the two companion papers.