An unusual suite of eclogitic, websteritic and transitional websteritic-lherzolitic diamonds from the Voorspoed kimberlite in South Africa: Mineral inclusions and infrared characteristics

The websteritic and the transitional websteritic-lherzolitic mantle source rocks of the Voorspoed diamonds likely formed through melt infiltration into mantle peridotite, possibly in the reaction envelope surrounding an ascending mantle plume. In order to account for the unusually low abundance of harzburgitic diamonds at Voorspoed, it is postulated that a primary, pre-existing suite of harzburgitic diamonds which have crystallised in the Mesoarchaean, was destroyed through heating and oxidation during the passage of magmas associated with the Ventersdorp large igneous province at 2.72 Ga, and which was subsequently followed by the crystallisation of a younger eclogitic and transitional websteritic-lherzolitic suite of diamonds.