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 us e of particle induced X-ray emission (PIXE) dynamic mapping and spot analys is. Two morphological types of gold were found: visible gold which is spati ally related to zones of high As concentration on detrital and authigenic p yrite surfaces, and invisible gold which is partially correlated with high As concentrations in authigenic pyrite grains, The spatial resolution of PI XE analysis allows the mapping of trace element distributions, at a few ppm level, in two dimensions, an application that is not accessible by electro n probe microanalysis (EPMA) and ore microscopy. This information is of cru cial importance in understanding the mechanisms of gold deposition in and o n pyrite surfaces, (C) 1999 Elsevier Science B.V. All rights reserved.