Empirical Pt_7Cu from an alluvial platinum concentrate and its significance for platiniferous quartz lodes in the Lubero region, DR Congo

摘要

An alluvial platinum grain from Lubero, DRC, is compositionally analogous to Pt_7Cu. This phase is so far unknown in nature, but is known from the binary platinum-copper system to have an ordered structure and formed below 500 °C, and as low as 100 °C. Such low temperatures rule out magmatic platinum mineralisation as source rock. The presence of previously reported inclusions of vein quartz and hematite in some alluvial grains of platinum, together with the relatively low formation temperatures of the Pt_7Cu compound, suggests that hydrothermal quartz lodes were the source of the platinum found in the Lubero alluvia.