Crustal Scale Resistivity Structure, Magmatic-Hydrothermal Connections, and Thermal Regionalization of the Great Basin

Abstract

Wideband MT profiling across the central Great Basin and flanking terrains by the University of Utah/EGI now reaches nearly 1000 km in length and just over 300 stations. Impedance phase tensor analysis indicates a clear north-south dominant trend to deep crustal electrical structure. Two-dimensional inversion of the data reveals an undulatory lower crustal conductor whose depths are greatest under the southern Modoc Plateau and elevated eastern Nevada. Global correlations of depth to top of this conductor with heat flow suggest an isotherm near 500 C. Resistivity thus correlates well with understanding that these regions have been relatively resistant to extension and have a somewhat reduced thermal regime. Particularly shallow reaches of this conductor occur under the Black Rock-Kumiva desert area and western Nevada generally, as well as under western Utah. This in turn is in keeping with enhanced degrees of extension there. Numerous crustal-scale breaks are seen connecting lower crustal magmatic underplating to the near-surface, sometimes to known geothermal systems. Even eastern Nevada exhibits some of these suggesting it may not be devoid of geothermal resources.