Antimony and other metal anomalies south of Stibnite, Valley County, Idaho

Results of geochemical investigations south of Stibnite, Valley County, Idaho, show that the distribution of Sb, As, Au, Zn, Ag, and Mo in mull ash and of Hg, in soil forms a highly anomalous area which is more than 1.5 km long and 1 km wide along the trace of the Meadow Creek fault, a major northstriking fault zone. In the report area the Meadow Creek fault is covered by deposits of Quaternary glacial debris ranging in thickness from several meters to more than 30 meters. Two other highly anomalous areas--one of Au, Zn, and Hg, and one of Zn, Ag, Hg, and Mo--correlate with silicified granodiorite along the trace of the Meadow Creek fault. These anomalies are not related to hnown Ore deponits and merit further investigation. The enrichment of metals in mull ash in the area of thick glacial debris suggests that the metals migrate from bedrock upward through the glacial debris, are taken up by the forest vegetation, and are concentrated in the mull as the litter from the vegetation-decays. The findings indicate that mull is the most useful geochemical sampling medium in the stibnite area because the bedrock is deeply buried beneath deposits of transported material such as colluvium or glacial debris.