Variations in whole-rock and mineral chemistries allow the recognition of four distinct groups of peridotite nodules within these kimberlite occurrences. Equilibration T estimates, together with general geochemical considerations, strongly suggest that the relatively ferriferous Group 1 (Cr-spinel wehrlites and lherzolites) and Group 2 (Al-spinel lherzolites) nodules represent basaltic cumulates of probable lower crustal origin. By contrast, the more magnesian peridotites are considered to have derived from the upper mantle, with the Group 3 nodules (Cr-spinel lherzolites and harzburgites) originating from shallower levels than those of Group 4 (garnet harzburgites).-J.M.H.
|Number of pages||15|
|Publication status||Published - 1984|