Why is Nevada in Hot Water? Structural Controls and Tectonic Model of Geothermal Systems in the Northwestern Great Basin

摘要

In the western Great Basin, the Walker Lane is a system of right-lateral strike-slip faults accommodating approx15-25percent of relative motion between the Pacific and North American plates. Relatively high rates of recent (<10 Ma) west-northwest extension absorb northwestward declining dextral motion in the Walker Lane, diffusing that motion into the Basin-Range. Abundant geothermal fields cluster in several northeast-trending belts in the northern Great Basin (e.g. Humboldt structural zone and Black Rock Desert region) and collectively define a broad, northeast-trending zone of high heat flow. Individual fields are largely controlled by north-northeast-striking normal faults. The Walker Lane begins losing displacement to the northwest in west-central Nevada near the southeast margin of the high heat-flow region. The abundant geothermal fields may therefore result from a transfer of northwest-trending dextral shear in the Walker Lane to west-northwest extension in the northern Great Basin. Enhanced extension favors dilation and deep circulation of aqueous solutions along north-northeast-striking faults. The individual belts of geothermal fields probably reflect loci of strain transfer.