Post-Archean formation of the lithospheric mantle in the central Siberian craton: Re-Os and PGE study of peridotite xenoliths from the Udachnaya kimberlite
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© 2015 Elsevier Ltd. The formation age of the Siberian cratonic mantle is not well established. Re-Os data on various mantle-derived materials brought up by kimberlite magmas have shown that it contains Archean components, but the reported ages range broadly (3.4 to < 1Ga). We report Re-Os isotope and PGE concentration data for a suite of 29 fresh, well-characterized xenoliths from the Udachnaya-East kimberlite representing all major peridotite rock types and a large part of the cratonic mantle profile. Several xenoliths with very low Os contents ( < 0.3 ppb) and/or high Re/Os ratios are not suitable for age estimates. The Os (and Ir) depletions are common in cpx-bearing spinel harzburgites and coarse garnet harzburgites, but are not found in deformed, high-T peridotites. Twenty refractory (Al < inf > 2 < /inf > O < inf > 3 < /inf > 0.1-1.6%) peridotites yield T < inf > RD < /inf > ages from 0.9 to 2.2Ga. T < inf > RD < /inf > for a subset of six high-Mg# (0.92-0.93), low-T (=930°C) spinel harzburgites and a single garnet harzburgite yield a narrow range from 2.0 to 2.2Ga with an average of 2.1±0.1Ga, which we consider the best estimate for the age of the melting event that initially formed the lithospheric mantle beneath Udachnaya. The T < inf > RD < /inf > estimates for less refractory (Mg# 0.907-0.919) deformed garnet peridotites show a greater range and are generally lower (0.9-2.0Ga; average 1.54±0.28Ga) apparently due to the effects of melt metasomatism on the initial melting residues. The predominant part of the mantle in the central Siberian craton formed in the Paleoproterozoic and not in the Archean, unlike cratons in southern Africa and North America. Minor older components reported earlier from Udachnaya may be fragments of pre-existing lithosphere trapped during stacking of melting residues formed about 2Ga ago. We argue that the formation of cratonic lithospheric mantle, with common high-Mg# (=0.92) and opx-enriched peridotites, was not limited to the Archean as previously thought, but continued in the Paleoproterozoic, i.e. that asthenospheric mantle was generally hot enough to experience high-degree melting on a large scale and thus sustain the "Archean" tectonic regime till much later in the Earth's history.
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The age and history of the lithospheric mantle of the Siberian craton: Re-Os and PGE study of peridotite xenoliths from the Obnazhennaya kimberliteIonov, D.; Carlson, R.; Doucet, Luc-Serge; Golovin, A.; Oleinikov, O. (2015)© 2015 Elsevier B.V. The formation age of the lithospheric mantle of the Siberian craton (one of the largest on Earth) is not well established; nearly all published whole-rock Re-Os data are for mantle xenoliths from a ...
Paleoproterozoic formation age for the Siberian cratonic mantle: Hf and Nd isotope data on refractory peridotite xenoliths from the Udachnaya kimberliteDoucet, Luc-Serge; Ionov, D.; Golovin, A. (2015)© 2014 Elsevier B.V. The formation age of the Siberian cratonic mantle is not well established as yet. Re-Os data on various mantle-derived materials have shown that it contains Archaean components, but the reported ...
High water contents in the Siberian cratonic mantle linked to metasomatism: An FTIR study of Udachnaya peridotite xenolithsDoucet, Luc-Serge; Peslier, A.; Ionov, D.; Brandon, A.; Golovin, A.; Goncharov, A.; Ashchepkov, I. (2014)The processes that control water distribution in nominally anhydrous minerals from peridotites are twofold. Melt depletion will remove water while metasomatism can potentially add water to these minerals. These processes ...