DETERMINATION OF THE PLATINUM-GROUP ELEMENTS IN SOUTH-AFRICAN KIMBERLITES BY NICKEL SULFIDE FIRE-ASSAY AND NEUTRON-ACTIVATION ANALYSIS

Ten kimberlites from various localities in South Africa have been anal ysed for all of the platinum-group elements (PGEs) and gold using a ni ckel sulphide fire-assay preconcentration followed by neutron activati on analysis (NAA). Problems encountered during the analysis of these s amples prompted a radio tracer study to test the recovery of the preci ous metals during firing, and then the subsequent dissolution of the a ssay button. The results of this study suggest solutions to the potent ial problems of incomplete melting of MgO-rich and CO2-rich during fir e-assay, and minimising losses of Pt, Pd and Au during dissolution. Fu rthermore, this improved procedure offers lower limits of detection th an previous methods which combined fire-assay and NAA. The concentrati ons of PGEs determined in this study of South African kimberlites are compared with previous partial analyses from the literature, indicatin g that earlier analyses may have seriously overestimated the concentra tions of some PGEs in kimberlites.