Platinum and Palladium in Mafic-Ultramafic Igneous Rocks, Northwestern Alaska

摘要

Extensive bodies of mafic-ultr-c igneous rocks occur in northwestern Alaska. Principal occurrences include Rabbit Creekf Avan River, Misheguk Mountain, Asik Mountain, and Shiktanneyak Mountain areas. Simples from sleeted sulphide-bearing zones contain some relatively high concentrations of platinum (Pt; 412-1826 parts per billion -ppb) and palladim (Pd; 343-1426 ppb). Within limits of resolution of optical microscopy, discrete phases consisting of Pt-Pd in major proportions were not recognized. These Pt-Pd concentrations are comparable to many reported concentrations associated with deposits of Pt-Pd-bearingmineralization elsewhere. Given the relatively low modal amounts of sulphides in the Alaska samples (2 to 5 percent), the high Pt and Pd values reported essentially represent concentrations in silicate rocks containing minor sulphides and oxides. There is a direct relationship between concentrations of copper and Pt-Pdf in individual samples, suggesting genetic affiliation.