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. The stream-sediment samples consisted mostly of active alluvium collected primarily from first-order (unbranched) and second-order (below the junction of two first-order) streams as shown on USGS topographic maps (scale = 1:62,500). Each sample was composited from several localities within an area that may extend as much as 150 ft from the site plotted on the map. Heavy-mi neral-concentrate samples We panned heavy-mineral-concentrate samples from the same active alluvium as the stream-sediment samples, but the material selected for panning was intentionally biased by collection from points of natural concentration of heavy minerals by stream processes. The material was panned until most of the quartz, feldspar, organic material, and clay-sized material was removed. The sample was air dried. Rock samples We collected rock samples from outcrops or exposures in the vicinity of the plotted site location. Most samples were collected from unaltered rock. Rock samples provide information on elements in rocks that have not been affected by alteration or mineralization. In addition, some altered and(or) mineralized rocks were collected. Water samples We collected water samples from springs. A 500-mL sample was taken at each site and stored in a new untreated plastic bottle. In addition, a 60-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 acidrinsed polyethylene bottle. Sample Preparation Only the stream-sediment samples required extensive preparation. Rock samples were simply crushed and then pulverized with ceramic plates to minus 0.15 mm. Water samples required no preparation beyond that done in the process of collecting them. The samples were air dried and sieved through minus-80-mesh stainless steel sieves. The portion of the sediment passing through the sieve was split and a representative fraction was saved for analysis. Panned concentrates were air dried and examined to determine mineral composition. A small split of each sample was separated and hand ground for spectrographic analyses. The entire remainder of each concentrate was saved for analysis. Sample Analysis Spectrographic method We analyzed the stream-sediment, heavy-mineral-concentrate, and rock samples for elements using a semiquantitative, direct-current arc emission spectrographic method (Grimes and Marranzino, 1968) The elements analyzed and their lower limits of determination are listed in Table 1. Spectrographic results were obtained by visual comparison of spectra derived from the sample against spectra obtained from standards made from pure oxides and carbonates. Standard concentrations are geometrically spaced over any given order of magnitude of ...
