Low-calcium garnet harzburgites from southern Africa: their relations to craton structure and diamond crystallization

Article Abstract:

The association of low-calcium garnet harzburgites and peridotitic diamonds was studied based on its occurrence in xenolith suites of the Kaapvaal craton in southern Africa. Rare earth and isotopic analyses have shown the similarity in geochemical and textural characteristics of the low-calcium garnet harzburgites and low-temperature lherzolites except for deficiencies in silicon, calcium, aluminum and iron and enrichment in magnesium and nickel of garnet harzburgites relative to lherzolite. Introduction of diamond in the Kaapvaal craton was postulated to have caused carbonate crystallization which caused calcium depletion in the associated garnets.

South Africa, Composition, Garnet, Mineralogy, Determinative, Determinative mineralogy

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Composition and thermal evolution of cratonic mantle beneath the central Archean Slave Province, NWT, Canada

Article Abstract:

Xenoliths found in the Torrie kimberlite pipes were used as the basis for studying the composition and thermal evolution of the upper mantle lithosphere in the central Archean Slave Province. The pyroxenite xenolith samples were found to register temperatures ranging between 850 and 1350 deg Celcius. The presence of the xenoliths was consistent throughout, exhibiting a noted richness in the presence of Calcium. Researchers have determined, using flexural analysis of the Kilohigok Basin, that the cratonic mantle has decreased up to fourfold in terms of geothermal gradient.

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Composition of the Siberian cratonic mantle: evidence from Udachanaya peridotite xenoliths

Article Abstract:

The bulk composition and mineral analyses of 41 garnet- and spinel-facies peridotite xenoliths from the Udachnaya kimberlite in the central Siberian platform are discussed. Similarities are observed between the bulk composition of perodotite from the Udachnaya and the Kaapvaal craton in southern Africa indicating a common origin. These include the high mg numbers of low-temperature peridotites and the wide dispersion in modal olivine contents.

Peridotite, Siberia

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