Mineral resources of the South Pequop Wilderness Study Area, Elko County, Nevada

Abstract

The South Pequop Wilderness Study Area (NV010-035) is in the Pequop Mountains, in northeastern Nevada. The area studied, 34,544 acres (approximately 54 square miles), is about equally divided by the crest of the range into eastand west-sloping tracts sparsely covered by pinyon pines and junipers. The geology was mapped in 1965-1971, and the mineral resource potential was investigated in 1984-1985. The geologic formations are mainly limestone and dolomite units, but one heterogeneous sequence, the Plympton Formation, includes beds of chert, shale, and phosphatic rocks. The area occupied by this formation is regarded as having a moderate mineral resource potential (likelihood of occurrence of undiscovered concentrations) for phosphate deposits. However, such deposits, if they exist, are not likely to be very large. In two areas within the study area, geochemical data suggest the possibility of concealed deposits of gold, silver, lead, zinc, and copper. The areas are regarded as having a moderate resource potential for these metals, but there is no indication of the grade or dimensions of these hypothetical deposits. Thermal history and structural conditions in the wilderness study area do not favor the formation and accumulation of oil and gas, and the study area is therefore regarded as having a low energy resource potential for these commodities. Common limestone and dolomite underlie almost the entire area of the wilderness study area, but they are of poor quality for all uses except as road metal. The resource potential of the study area for thick beds of high-purity limestone and dolomite is low. Common sand and gravel deposits are plentiful in the study area, but they are in no way unique, and no local demand is likely to materialize that cannot be supplied by deposits outside the study area. The study area has a low resource potential for specialty sand and gravel. Character and Setting The area studied covers 34,544 acres (about 54 square miles) of the southern Pequop Mountains, a northeast-trending range in the central part of the Great Basin (fig. 1). The relief within the area from the lowest point on the northwest border to the highest peak is 3,281 feet, and the highest point is 8,952 feet above sea level. Most of the area is covered by a thin growth of stunted pinyon pines and junipers. Lower slopes are covered by grasses and bushes, mainly sagebrush. The wilderness study area is far from towns and ranches, but it can be reached quite easily by gravel and dirt roads from Interstate Highway I-80, which crosses the Pequop Mountains 24 miles to the north, and from U.S. Highway 93 to the west and southwest. Unimproved roads and trails traversable by four-wheel-drive vehicles and pickup trucks penetrate the study area in some canyons, border it on the south and west, and reach its boundary at several points on the east side. The area is therefore quite accessible, but its remoteness from towns and ranches keeps human traffic to a minimum. The geologic terrane in the wilderness study area is one principally of folded limestone and dolomite beds that form north-south-trending ledges and ridges. Among these predominantly carbonate beds is a stratigraphic unit known as the Plympton Formation, a heterogeneous sequence that includes chert, silty beds, shale, and phosphatic beds. This formation is of interest because of its content of phosphorus, an essential ingredient of fertilizer. A small granitic intrusive stock is present in the central part of the area. Identified Resources An identified resource is one whose location, grade, quality, and quantity are known or can be estimated from specific geologic evidence (see resource/reserve classification chart in appendix). Identified reSouth Pequop Wilderness Study Area B1