A HYDROTHERMAL PGE DEPOSIT IN SOUTHEASTERN WY

Although rare, four non-magmatic PGE deposits have been discovered, including the historic New Rambler mine in southeastern Wyoming. Here, high Pd and Pt are associated with hydrothermally altered, variably deformed amphibolitic mafic-to-ultramafic rocks. This system likely formed via the infiltration of large volumes of hydrothermal fluids into sheared and faulted rocks of the 1778 ± 2 Ma Mullen Creek Mafic Complex (MCMC) and Cheyenne Belt. The local New Rambler geology is obscured by thick Quaternary gravel, alluvial deposits, and dense forest litter. Despite these challenges, 240 surface samples were collected from the New Rambler area and analyzed for PGEs, Au, and a suite of elements. Geostatistical results were interpolated with inverse distance weighted and ordinary kriging methods. Geochemical maps of PGE pathfinder elements (As, Co, Cu, Ni, Pd, Pt) revealed what are interpreted as two unique geochemical anomalies that merit further exploration: (1) a base and precious metal hotspot overlying altered, deformed amphibolite and metapyroxenite; and (2) a sharp, roughly E-W trending geochemical discontinuity in Fe and pathfinder elements just north of the New Rambler mine. Anomaly 2 is interpreted to be a sharp geologic contact and/or the continuation of a shear zone mapped by Hausel and Sutherland (2005). These results reveal the applicability and utility of geostatistical analyses and interpolations for mineral exploration in geologically complex areas and will guide future PGE exploration in the New Rambler area.