| A method was developed to distinguish between ilmenites from different mantle xenoliths found at Kimberley, South Africa: Granny Smith, dunites, orthopyroxenites, MARID and rutile-ilmenite intergrowths. The method employs a number of oxide screens based on MgO, TiO2 and Cr2O 3 and systematically eliminating whole fields defined by mathematical equations. The classification scheme is useful to better understand the source of the ilmenite and has been applied to ilmenite xenocrysts from four diamond mines in the Kimberley area: Bultfontein, Kamfersdam, Otto's Kopje and Wesselton. A relationship between ilmenite chemistry and its paragenesis exists, but it is not as clear as in the Cr-poor megacrysts. A more complex process is responsible for the crystallization of ilmenite in the five different suites at Kimberley, and metasomatim by a Fe-Ti rich magma or melt, similar in composition to the parent magma of the South African megacrysts, plays an important role in ilmenite formation. |
