Analytical results and sample locality maps of stream-sediment, panned-concentrate, rock, and water samples from the West and East Palisades Roadless Areas, Idaho and Wyoming

Abstract

Bureau of Mines to survey certain areas on Federal lands to determine their mineral resource potential. Results must be made available to the public and be submitted to the President and the Congress. This report presents the results of a geochemical survey of the West and East Palisades Roadless Areas in the Targhee and Bridger National Forests, Teton and Bonneville Counties, Idaho, and Teton and Lincoln Counties, Wyoming. The West and East Palisades Roadless Areas were classified as a (further planning area) during the Second Roadless Area Review and Evaluation (RARE II) by the U.S. Forest Service, January 1979. JtTHODS OF STUDY Sample Collection We collected samples at 603 sites (plate 1). We analyzed 338 streamsediment samples, 65 panned-concentrate samples, 186 rock samples, and 14 water samples (Tables 4-7), for a sampling density of about 1 sample per 1 mi 2 for the stream sediment and heavy-mineral concentrate, and about 1 sample per 2 mi for the rock. The drainage basins ranged fromV2to 20 mi. Stream-sediment samples Analyses of the stream-sediment samples represent the chemistry of the rock material eroded from the drainage basin upstream from each sample site. Such information is useful in identifying those basins which contain concentrations of elements that may be related to mineral deposits. Water samples We collected water samples from springs and seeps. A 500-mL sample was taken at each site and stored in a new untreated plastic bottle. In addition, a 200-mL sample was filtered through a 0.45-micrometer filter, was acidified with reagent-grade concentrated nitric acid to pH 2, and was stored in an acid-rinsed polyethylene bottle. Sample Preparation Only the stream-sediment samples required extensive preparation. Rock samples were simply crushed and then pulverized. Water samples required no preparation beyond that done in the process of collecting them. Stream-sediment samples were air dried in metal-free paper envelopes and sieved through an 80-mesh (177 micron) stainless steel screen. The fraction of each sample passing through the sieve was saved and split into two portions one for analysis and the other for archival storage. Panned-concentrates were air dried and examined to determine mineral composition. A small split of each sample was separated and hand ground for spectrographic analysis. The entire remainder of each concentrate was weighed and chemically analyzed (via atomic absorption) for gold content. Rock samples were crushed in a jaw crusher to minus 6 mm and ground to minus 0.15 mm in a vertical pulverizer equipped with ceramic plates. This fine material was then split into portions for analysis and archival storage. Sample Analysis Spectrographic method We analyzed the stream-sediment, heavy-mineral-concentrate, and rock samples for 31 elements using a semiquantitative, direct-current arc emission spectrographic method (Grimes and Marranzino, 1968) (Table 3). Spectrographic results were obtained by visual comparison of spectra derived from the sample against spectra obtained from st...