Trace elements in platinum group minerals studied using nuclear microscopy

A combination of μ-PIXE and μ-RBS has been used to study concentrations and distributions of trace elements in platinum group minerals from eluvial and alluvial deposits from the western seaboard of North America. Thirteen of the pure element standards, used in the EPMA investigation, were first analysed by μ-PIXE. These analyses were used to establish limits of confidence in the analytical technique. It is shown that using simultaneous RBS to determine the matrix composition and incident charge accurate PIXE analysis is possible without standards. Natural grains of Pt-Fe and Os-Ir-Ru alloys were then analysed and traces of Cu, Fe, Ni, Ti, Ru, Rh, Pd, Cr, etc., were determined at levels ranging from 80 ppm to 5000 ppm. It is shown that while there may be minor variations between localities, the trace element distribution within the grains studied is essentially uniform.