PIXE microanalysis of gold-pyrite associations from the Kimberley Reefs, Witwatersrand basin, South Africa

The nuclear microprobe has been used to examine gold-pyrite associations in the gold-bearing Kimberley Reefs of the Witwatersrand basin through the use of particle induced X-ray emission (PIXE) dynamic mapping and spot analysis. Two morphological types of gold were found: visible gold which is spatially related to zones of high As concentration on detrital and authigenic pyrite surfaces, and invisible gold which is partially correlated with high As concentrations in authigenic pyrite grains, The spatial resolution of PIXE analysis allows the mapping of trace element distributions, at a few ppm level, in two dimensions, an application that is not accessible by electron probe microanalysis (EPMA) and ore microscopy. This information is of crucial importance in understanding the mechanisms of gold deposition in and on pyrite surfaces, (C) 1999 Elsevier Science B.V. All rights reserved.