Did diamond-bearing orangeites originate from MARID-veined peridotites in the lithospheric mantle?

A. Giuliani, D. Phillips, J.D. Woodhead, V.S. Kamenetsky, Marco Fiorentini, R. Maas, A. Soltys, R.A. Armstrong

    Research output: Contribution to journalArticle

    49 Citations (Scopus)

    Abstract

    © 2015 Macmillan Publishers Limited. All rights reserved. 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.
    Original languageEnglish
    Article number6837
    Number of pages10
    JournalNature Communications
    Volume6
    DOIs
    Publication statusPublished - 2015

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