ABSTRACT
Platinum-group elements have been analysed in 66 samples of several Southern African flood basalt sequences, including the Dominion, Ventersdorp, Hekpoort, Machadodorp, Karoo (in Lesotho and the Tuli syncline) and Etendeka lava piles. The individual sequences contain between 10 and 52 ppb Pt+Pd, and up to 1.49 ppb Ir. All sequences except for the Tuli appear to be undepleted in Cu, but all except the oldest flood basalts are depleted in PGE relative to Cu. This suggests that the magmas have experienced but minor sulphide segregation during ascent and have to be considered poor exploration targets for massive magmatic sulphides. In all sequences where we have good stratigraphic control, the lowermost flows appear to be most depleted in metals, suggesting that contamination occurred particularly in the first magma batches ascending through the crust.
