of identified resources 6 Assessment of mineral resource potential 6 Geology 6 Geochemical studies 6 Geophysical studies 7 Mineral and energy resource potential 8 References cited 9 Appendixes Definition of levels of mineral resource potential and certainty of assessment 12 Resource/reserve classification 13 Geologic time chart 14 FIGURES 1. Index map showing location of the Fish Creek Rim Wilderness Study Area, Lake County, Oregon 2 2. Map showing mineral resource potential and generalized geology of the Fish Creek Rim Wilderness Study Area, Lake County, Oregon

Character and setting 1 Identified resources 1 Mineral resource potential 1 Introduction 3 Area description 3 Previous and present investigations 3 Acknowledgments 5 Appraisal of identified resources 5 Mines and prospects, mining claims, and leases 5 Reserves and identified resources 5 Recommendations for further study 6 Assessment of mineral resource potential 6 Geology 6 Geochemical studies 6 Geophysical studies 7 Mineral and energy resource potential 8 References cited 8 Appendixes Definition of levels of mineral resource potential and certainty of assessment 12 Resource/reserve classification 13 Geologic time scale 14 FIGURES 1. Index map showing location of the Orejana Canyon Wilderness Study Area, Harney County, Oregon B2 2. Map showing mineral resource potential and generalized geology of the Orejana Canyon Wilderness

resources 1 Mineral resource potential 1 Introduction 2 Area description 3 Previous and present investigations 3 Appraisal of identified resources 3 Mining and mineral exploration history 3 Reserves and identified resources 5 Recommendations for further work 5 Assessment of mineral resource potential 5 Geology 5 Geochemical studies 6 Geophysical studies 6 Mineral and energy resources 7 References cited 8 Appendixes Definition of levels of mineral resource potential and certainty of assessment 11 Resource/reserve classification 12 Geologic time chart 13 FIGURES 1.

ed with minor modifications from: Taylor, R. B., and Steven, T. A., 1983, Definition of mineral resource potential: Economic Geology, v. 78, no. 6, p. 1268-1270. Taylor, R. B., Stoneman, R. J., and Marsh, S. P., 1984, An assessment of the mineral resource potential of the San Isabel National Forest, south-central Colorado: U.S. Geological Survey Bulletin 1638, p. 40-42. Goudarzi, G. H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey Open-File Report 84-0787, p. 7, 8. RESOURCE/RESERVE CLASSIFICATION IDENTIFIED RESOURCES

The Roberts Wilderness Study Area (NV-060-541) encompasses 15,090 acres and includes Roberts Creek Mountain, Cooper Peak, and Western Peak, three of the highest peaks in the Roberts Mountains, Eureka County, Nev. Field work for this report was carried out between May and August 1984 and augmented geologic mapping and other geologic studies that have continued for more than 20 years.Stream-sediment samples from the Kelley Creek drainage contain anomalous amounts of silver, lead, and zinc; the area including this drainage has low mineral resource potential for these metals in hydrothermal veins that follow faults and shear zones in carbonate host rock.The abandoned Kelley mine produced 397 tons of silver, lead, and zinc ore prior to 1940.Some rock samples from outcrops along the east edge of the study area contain anomalous amounts of gold and silver, as well as a suite of volatile elements including arsenic, antimony, and mercury that locally are indicators of precious-metal mineralization.These samples are associated with silicified zones that formed in dolomitic rock beneath the Roberts Mountains thrust fault.These zones have high, moderate, and low resource potential for gold and silver.Two similar areas of silicified and altered dolomite in the southwest part of the study area have moderate-to-low resource potential for gold and silver.An east-west trending zone in the central part of the study area and two areas near its western edge contain anomalous amounts of gold and silver in altered dolomite and limestone associated with major faults and shear zones.These areas have moderate-to-low potential for gold and silver resources.Several mining companies have done extensive exploration for gold and silver and have claim blocks that extend into the study area from the east, west, and south (pi.1; Benjamin and Johnson, 1986).The areas claimed are included in areas of high and moderate resource potential in this report.