Geochemical exploration for platinum-group element deposits in Miyi County, Sichuan Province, Southwestern China

Abstract

A large Pt–Pd geochemical province within the Emeishan basalt province has been identified previously and was considered as an exploration target for platinum-group element (PGE) mineralization. To evaluate thoroughly the prospect of economic Pt–Pd mineralization in this region, a series of geochemical surveys was conducted in a selected area, with an exploration strategy involving the progressive reduction of the target area and stepwise increase in the sampling density. A regional Pt and Pd geochemical anomaly was delineated by a stream sediment survey at a sampling density of 1 sample km −2 over an area of mafic intrusive bodies and basalts in Miyi County, Sichuan Province. In a follow-up phase, three local Pt and Pd geochemical anomalies were defined by data from a stream sediment survey with a density of 4 samples km −2 . Finally, PGE mineralization within a gabbroic rock was discovered in the geochemical anomalies delineated by the following more detailed survey, namely a soil survey with a 100 m × 20 m sampling grid. The level of Pt+Pd mineralization was 0.33 μg g −1 . A new concealed mafic–ultramafic intrusive body containing PGE mineralization was predicted.The success of this case has provided an excellent example of how to identify possible PGE target areas in the basalt environment using geochemical surveys at various scales.