LIDAR AND HYPERSPECTRAL ANALYSIS OF MINERAL ALTERATION AND FAULTING on THE WEST SIDE OF THE HUMBOLDT RANGE, NEVADA

We carried out a program of hyperspectral and LiDAR imaging of the Humboldt River basin to gain an understanding of the relationship of faulting and mineral alteration in a geothermal setting. The basin is part of the Battle Mountain heat flow high, which is located in the transition (as seen by GPS studies) between west-directed and northwest-directed movement relative to stable North America. In the southern (Rye Patch) region a set of faults cut 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 height of the Lake 12,500 + 500 years ago. We find no signs of surface mineral alteration in the Rye Patch area in spite of the existence of these faults. Farther north, in the Humboldt House region, we find abundant evidence of alteration products, including sinter, travertine, montmorillonite, hematite and jarosite. This alteration is widespread, and corresponds to young faulting in only one location. The LiDAR data show numerous examples of fluid venting, including several mud or sand volcanoes, a large field of gryphons (mud volcanoes less than one m high), and scattered evidence of sand blows. Some of these fluid vents may have been associated with seismicity, and at least the 1915 Pleasant Valley earthquake 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.