Browsing by Author "Coe, Nancy"

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    Petrogenesis of the Swartruggens and Star Group II kimberlite dyke swarms, South Africa
    (2004) Coe, Nancy; Le Roex, Anton; Gurney, John J
    The Swartruggens (156 Ma) and Star (128 Ma) kimberlites are two Group II, diamondiferous, hypabyssal kimerlite dyke swarms, situated in the Northern Province and the Free State respectively, South Africa. Representative samples from all dykes exposed in the mining operations, the Main and Changhouse Dykes, South Fissure and the barren Muil Dyke at Swartruggens, and the Wynandsfontein, East Star, Clewer, Byrnes and Barren dykes at Star, have been analysed for their major and trace element contents and Sr, Nd and Hf isotope compositions. Primary kimberlite magma chemistry is subjected to considerable modification due to the incorporation of both mantle and crustal material during ascent to the surface, crystal fractionation, and post-emplacement alteration by deuteric fluids. This study aims to constrain the effects of these processes, and thus to identify least-modified, close-to-primary, parental magma compositions, with the view to understanding the source region characteristics of, and the petrogenetic processes giving rise to, these kimberlites.