Platinum-group element and sulphide mineralogy in ultramafic complexes at Western Adriamena, Madagascar

McDonald, Iain

Publication date

March 2008

DOI

10.1179/174327508X309678

Publisher

Maney Publishing

Abstract

Small (<2 km diameter), ultramafic intrusive complexes in the Andriamena region of Madagascar carry high concentrations of platinum-group elements (PGE). The PGE mineralisation at Andriamena is unusual in that it is not obviously associated with abundant sulphide or chromitite layers or pods, as in many layered complexes and Alaskan-type intrusions. Mineralogical investigation of rocks from one complex, designated UM2, has revealed a complex array of Pt and Pd-bearing platinum-group minerals (PGM) that tend to be concentrated interstitially between olivine crystals in dunite units. These PGM are dominated by PGE arsenides and stibioarsenides, accompanied by a small population of Pd oxides that occur in unit close to the surface and appear t...