Mineral resources of the Riordans Well Wilderness Study Area, Nye County, Nevada

Abstract

The Riordans Well Wilderness Study Area (NV-040-166) lies in the Basin and Range physiographic province of east-central Nevada (fig. 1). The U.S. Bureau of Land Management (BLM) requested that a mineral survey of 37,542 acres of the wilderness study area in Nye County, Nev., be conducted by the U.S. Geological Survey (USGS) and the U.S. Bureau of Mines (USBM) during 1983, 1985, and 1986. New geologic mapping of the area was completed, geochemical sampling of the area was conducted, geophysical characteristics were evaluated, and unpatented claim blocks in the area were investigated. There are no identified (known) mineral resources in the study area. Several types of undiscovered mineral resources may be present in the area. The mineral resource potential for each type is given below. The Riordans Well Wilderness Study Area has high energy resource potential for petroleum (fig. 2), although specific traps have not been identified. Almost half of the area has been leased for oil and gas (fig. 3). Moderate mineral resource potential is designated for three types of metal occurrence in two parts of the study area (fig. 2). The western part of the study area has moderate potential for tungsten and polymetallic base-metal (copper, lead, zinc, molybdenum, and bismuth) deposits in hydrothermal (low-to medium-temperature) replacement deposits in low-grade metamorphic rocks and for gold and silver in quartz veins associated with the replacement mineralization. The southeastern and eastern parts of the study area have moderate potential for gold in disseminated deposits associated with jasperoid occurrences. The remainder of the area has low resource potential for other metals, nonmetals (magnesite, high-purity limestone or dolostone), or other energy resources (geothermal energy, uranium, and coal). Character and Setting The Riordans Well Wilderness Study Area is in the northern Grant Range 18 mi southeast of Currant, northeastern Nye County, Nev. (fig. 1). Improved and unimproved roads provide access to the eastern and western sides of the wilderness study area. Old unimproved roads along the northern, northwestern, and southwestern boundaries of the wilderness study area are generally impassable. The eastern side of the Grant Range is topographically gentle and generally heavily forested; the western side is cliffy and deeply dissected. The total relief is more than 4,500 ft (feet) between Railroad Valley, west of the wilderness study area, and the highest point on an unnamed peak in the southern part of the area (9,352 ft). The Grant Range is an east-tilted fault block. The faulting exposed a stratigraphic section, from west to east, of thick carbonate sedimentary rocks of the Paleozoic (see geologic time scale in Appendix) continental shelf that are overlain by Tertiary basin deposits and by a sequence of Tertiary volcanic and basin-fill deposits. The oldest exposed Paleozoic rocks are metamorphosed. Rocks of the Grant Range show a complex structural history developed during Mesozoic compressional and Tertiary extensional events. The wilderness study area is north of the Troy and Willow Creek mining districts (fig. 1) and contains three groups of unpatented lode claims (fig. 3). Riordans Well Wilderness Study Area H1