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The Little Humboldt River Wilderness Study Area (NV-010-132) in northern Nevada is underlain by faulted volcanic rocks. The study area has no identified mineral resources (fig. 1). Numerous mining companies are actively exploring for gold in and around the wilderness study area. Different parts of the area have a high, medium, or low mineral resource potential for disseminated gold deposits and zeolites. Some areas have an unknown mineral resource potential for bedded barite and disseminated gold in rocks beneath the volcanic cover. The entire study area has a low resource potential for uranium and thorium, diatomite, tin, arsenic, antimony, silver, and mercury, oil and gas, geothermal energy, and sand and gravel. Character and Setting The Little Humboldt River Wilderness Study Area includes 40,000 acres (66 square miles) in western Elko County, northern Nevada (fig. 2). It occupies a broad, sage-covered upland basin surrounded on the west, south, and east by ridges. The study area can be reached by good to very poor dirt roads from the south, west, and north. Elevations range from 5,079 ft (feet) to 7,266 ft, and the South Fork of the Little Humboldt River has incised a narrow canyon that longitudinally bisects the wilderness study area. The study area is between the predominantly volcanic Snake River Plain volcanic province to the north and the structurally complex Basin and Range province to the south. Faulted and deformed older sedimentary and igneous rocks in the Basin and Range province are exposed in northtrending mountains that are separated by broad valleys filled with alluvium. In the transition zone between the two terranes, the volcanic rocks partly to completely cover the older rocks. The wilderness study area is underlain by a complex, interlayered sequence of volcanic rocks that were erupted between about 10 and 15 m.y. (million years) ago. The oldest rocks are rhyolitic flows and tuffs and lesser amounts of ash-rich sedimentary rocks and andesitic flows, dikes, and tuffs. These rocks were cut by steep faults that produced a large, north-trending basin. Ash-flow tuffs were erupted into this basin as it developed, forming the widespread tuff of the Little Humboldt River. Subsequently, widespread shallow lakes covered surrounding areas, and large volumes of crystal-rich rhyolitic flows were erupted just west of the wilderness study area. About 10 m.y. ago, basalt flows were erupted near the northeastern edge of the study area. Active faulting during volcanic activity produced a complex relation between volcanic units and various fault systems. |
