LANDSCAPE GEOCHEMISTRY FOR THE HUMBOLDT RIVER BASIN, NORTHERN NEVADA

Mineral resource potential and geochemical baselines of the Humboldt River basin were evaluated by a combined stream sediment and soil geochemistry survey. More than 7,000 samples, collected on average at 1 sample per 16 km2 grid cell, were analyzed by ICP-40 (total digestion) and ICP-10 (partial digestion). The geochemical data are portrayed as groups by standard deviation relative to the mean and plotted on a 1:500,000-scale topographic basemap. These thematic maps are useful in identifying the distribution of anomalous element concentrations, in some cases highlighting previously unrecognized anomalies such as in the area of Snake Mountains where As, Ag, Ba, Cu, Ni, Zn, and Au have high concentrations. Interpolated thematic maps are generated using normalized geochemical data and by applying a minimum curvature gridding algorithm. The results are continuous surface models of elements that are ideal for GIS analysis. The GIS data viewing software, ESRI ArcExplorer and ERDAS MapSheets Express, provide an interactive data querying capability and dynamic tool for the analysis of thematic maps and landscape geochemistry datasets. This GIS software enables the user to view geochemical data simultaneously with geology, mines and prospects, topography, and other cartographic base layers. The results of these studies can now be downloaded from the following USGS website: http://pubs.usgs.gov/mf/2003/mf-2407/.