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

journal contribution
posted on 2023-05-26, 09:40 authored by Giuliani, A, Phillips, D, Woodhead, JD, Vadim Kamenetsky, Fiorentini, ML, Maas, R, Soltys, A, Armstrong, R
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.

History

Publication title

Nature Communications

Volume

6

Article number

6837

Number

6837

ISSN

2041-1723

Publisher

Macmillan Publishers Limited

Publication status

  • Published

Repository Status

  • Restricted

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