Remote sensing analysis of structure and geothermal potential of the Humboldt Block, Nevada

Fluid flow along normal faults has created much of the geothermal energy that is currently being exploited in the Basin & Range. We used remote sensing (HyMap, ASTER) data and field-based methods in the Humboldt Block of the northwest Basin & Range to map fault zones and the surface distribution of minerals associated with hydrothermal fluid flow. The Humboldt Block lies on the Battle Mountain High heat flow area (>100 m/V/m²), and has very high shallow water temperatures of around 200° F. This area has undergone large amounts of extension from Oligocene to the present, accommodated along large, range-bounding normal faults. The western flank of the Humboldt Range is bounded by a normal fault that trends N-NE, dips W, and brings into contact Mesozoic sedimentary and volcanic rocks with Quaternary deposits. The structural setting, high heat flow, and high shallow water temperatures suggest significant geothermal potential for the Humboldt Block. We carried out the remote sensing study in two stages. We created fault maps by overlaying ASTER data onto a DEM, and mapping lithologic changes and structurally controlled lineations that were distinct from expected topographic patterns. This revealed two distinct fault patterns: N-NE trending faults and NW-SE trending faults. We then used HyMap (hyperspectral) data to identify and map minerals associated with hydrothermal fluid flow and their relation to regional structure. Sinter was mapped in the Humboldt River Valley along two distinct N-NE trends. Kaolinite was mapped in the Humboldt Range along the range front fault, and NW-SE trends.