LiDAR and hyperspectral analysis of mineral alteration and faulting on the west side of the Humboldt Range, Nevada

Abstract

In order to evaluate the setting of the Humboldt–Rye Patch geothermal field, we carried out a program of hyperspectral and light detection and ranging (LiDAR) imaging of the Humboldt River basin to test (1) whether fault patterns, surface mineral alteration, and mud volcanoes in the Humboldt–Rye Patch district offer the potential for additional geothermal exploration sites; (2) whether mud diapirism in this region could be caused by seismic shaking; and (3) whether significant improvements in exploration can be made using these remote-sensing tools in addition to the more traditional techniques. In the southern (Rye Patch) region, a set of faults cuts the surface of the alluvial fans, and several faults cut shorelines of Lake Lahontan. These shorelines lie at an elevation of 1290 m, which corresponds with the elevation of the Lake 12,500 ± 500 yr ago. We find no signs of surface mineral alteration in the Rye Patch area in spite of the existence of these faults and known alteration at depth. Farther north, in the Humboldt House region, we find abundant evidence of alteration products, including siliceous sinter, carbonate, montmorillonite, hematite, and jarosite. This alteration is widespread, and corresponds to young faulting in only one location. The LiDAR data show at least two mud volcanoes and a large field of low-carbonate mounds. Some of these (apparently) diapiric features may have been associated with seismicity, and both active and paleoseismic events would have been sufficiently close and energetic to have initiated liquefaction in this region. Such liquefaction events would have been more likely, however, during the high stands of Lake Lahontan, when the ground would have been saturated, consistent with reported ages on rocks correlated with the carbonate mounds. We propose further geothermal exploration based on these results.