A suggested origin of MARID xenoliths in kimberlites by high pressure crystallization of an ultrapotassic rock such as lamproite

Waters, Frances G.

doi:10.1007/bf00402210

Cited by 81 publications

(43 citation statements)

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“…Sweeney et al 27 noted that the bulk major element composition of MARID rocks could be obtained by subtracting the composition of olivine and carbonates from a bulk orangeite composition. In addition, the Sr and Nd isotopic composition of several MARID rocks overlap with the field defined by orangeites 19 . It is therefore possible that a MARID-veined peridotitic mantle could represent the source of orangeite melts.…”

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confidence: 93%

“…MARID rocks have been transported from the lithospheric mantle to the Earth's surface by kimberlite, orangeite and lamprophyre magmas from various localities worldwide [18][19][20][21][22] . MARID rocks represent an extreme example of mantle metasomatism because of their exceptional enrichment in alkalis, LREE, HFSE (for example, Ti, Zr, Nb) and volatile species, primarily H 2 O (ref.…”

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confidence: 99%

“…MARID rocks represent an extreme example of mantle metasomatism because of their exceptional enrichment in alkalis, LREE, HFSE (for example, Ti, Zr, Nb) and volatile species, primarily H 2 O (ref. 19). For this reason, MARID rocks have been frequently invoked to account for the origin of alkalirich mafic-ultramafic magmas [23][24][25][26] , with the notable exception of orangeites.…”

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confidence: 99%

“…The Kimberley area is unique because it hosts kimberlites (B81-95 Myr ago 16,[28][29][30] ) that were emplaced after the orangeites of the Barkly West-Boshof district (115-128 Myr ago 29,31 ; Fig. 2), and the Kimberley kimberlites host a variety of metasomatized mantle xenoliths, which have been extensively studied 11,12,18,19,[32][33][34][35][36][37] . Thus, mantle xenoliths entrained by the Bultfontein kimberlite can be considered representative of the same mantle lithosphere that produced the Barkly West-Boshof orangeites.…”

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confidence: 99%

“…2). MARID xenoliths are relatively common in the Kimberley kimberlites 12,18,19,35,39,40 . The two samples studied here exhibit coarse-grained foliated textures, with compositional banding related to the preferential concentrations of K-richterite and phlogopite in discrete layers (Fig.…”

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confidence: 99%

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

et al. 2015

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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, H 2 O and CO 2 -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-amphibolerutile-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.

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confidence: 99%