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Abstract

Kimberlites and orangeites (previously named Group-II kimberlites) are small-volume igneous rocks occurring in diatremes, sills and dykes. They are the main hosts for diamonds and are of scientific importance because they contain fragments of entrained mantle and crustal rocks, thus providing key information about the subcontinental lithosphere. Orangeites are ultrapotassic, H2O and CO2-rich rocks hosting minerals such as phlogopite, olivine, calcite and apatite. The major, trace element and isotopic compositions of orangeites resemble those of intensely metasomatized mantle of the type represented by MARID (mica-amphibole-rutile-ilmenite-diopside) xenoliths. Here we report new data for two MARID xenoliths from the Bultfontein kimberlite (Kimberley, South Africa) and we show that MARID-veined mantle has mineralogical (carbonate-apatite) and geochemical (Sr-Nd-Hf-O isotopes) characteristics compatible with orangeite melt generation from a MARID-rich source. This interpretation is supported by U-Pb zircon ages in MARID xenoliths from the Kimberley kimberlites, which confirm MARID rock formation before orangeite magmatism in the area.

Item Type:	Article
Authors/Creators:	Giuliani, A and Phillips, D and Woodhead, JD and Kamenetsky, VS and Fiorentini, ML and Maas, R and Soltys, A and Armstrong, R
Journal or Publication Title:	Nature Communications
Publisher:	Macmillan Publishers Limited
ISSN:	2041-1723
DOI / ID Number:	https://doi.org/10.1038/ncomms7837
Copyright Information:	Copyright 2015 Macmillan Publishers Limited
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