Thermochronometric Constraints on the Extent and Longevity of a Geothermal System in an Extensional Tectonic Setting, Wassuk Range, Nevada
Kyle E. Gorynski
University of Kansas, Dept. of Geology Lawrence, Kansas;
Extensional tectonic settings have long been a focus of geothermal exploration in light of the tectonic heat advection in the footwalls of normal faults coupled with magmatism and fracture permeability in the hanging wall rocks. Recent work on occurrence models for geothermal resources has identified thermochronometric ages as potentially key elements in exploring for areas that contain sufficient heat to constitute a utility-grade geothermal resource. This case study in the Hawthorne-Wassuk Range region, Nevada, attempts to illustrate the utility of this approach. (U-Th)/He thermochronometric analyses and thermal modeling of the Wassuk Range footwall should reveal whether sufficient advection has occurred through exhumation, faulting, or flow of hot fluids, to power an electrical-grade geothermal resource. The range is a westward tilted fault block of pre-Cenozoic rocks overlain by Miocene strata that underwent large-magnitude extension in the middle Miocene and renewed range-front faulting since the Pliocene. Detailed mapping and 40Ar/39Ar age dating of progressively tilted Miocene and younger volcanic and sedimentary rocks on the tilted (60-70˚) western range flank will be coupled with high-density apatite and zircon (U-Th)/He thermochronometry (~90 samples) to reconstruct the exhumation and tilting history and thermal evolution of the central Wassuk Range. This study will shed light on the role of syn-extensional heat-advection, footwall fracture permeability, and magmatism and the longevity and nature of the geothermal anomaly in the central eastern Wassuk Range.
AAPG Search and Discovery Article #90094 © 2009 AAPG Foundation Grants in Aid