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TitleA Palaeoproterozoic diamond-bearing lithospheric mantle root beneath the Archean Sask Craton, Canada
AuthorCzas, J; Pearson, D G; Stachel, T; Kjarsgaard, B AORCID logo; Read, G H
SourceLithos vol. 356-357, 105301, 2019 p. 1-14,
Alt SeriesNatural Resources Canada, Contribution Series 20190572
Mediapaper; on-line; digital
File formatpdf; html
Lat/Long WENS-110.0000 -104.0000 56.0000 52.0000
Subjectseconomic geology; geochemistry; Science and Technology; Nature and Environment; mineral potential; mineral deposits; diamond; basement geology; lithology; igneous rocks; intrusive rocks; kimberlites; mantle; lithosphere; craton; trace element analyses; major element analyses; isotopic studies; osmium; garnet; phase equilibria; pressure-temperature conditions; thermal analyses; Archean; Fort à la Corne Kimberlite Field; Sask Craton; Trans Hudson Orogen; Canadian Shield; Paleoproterozoic; Star Kimberlite; Orion South Kimberlite; platinum group elements; Phanerozoic; Mesozoic; Cretaceous; Precambrian; Proterozoic
ProgramGEM: Geo-mapping for Energy and Minerals Diamonds
Released2019 11 21
AbstractThe recently recognised Sask Craton, a small terrane with Archean (3.3-2.5 Ga) crustal ages, is enclosed in the Paleoproterozoic (1.9-1.8 Ga) Trans Hudson Orogen (THO). Only limited research has been conducted on this craton, yet it hosts major diamond deposits within the Cretaceous (~106 to ~95 Ma) Fort à la Corne (FALC) Kimberlite Field. This study describes major, trace and platinum group element data, as well as osmium isotopic data from peridotitic mantle xenoliths (n = 26) from the Star and Orion South kimberlites. The garnet-bearing lithospheric mantle is dominated by moderately depleted lherzolite. Equilibration pressures and temperatures (2.7 to 5.5 GPa and 840 to 1250 °C) for these garnet peridotites define a cool geotherm indicative of a 210 km thick lithosphere, similar to other cratons worldwide. Many of the peridotite xenoliths show the major and trace element signatures of carbonatitic and kimberlitic melt metasomatism. The Re-Os isotopic data yield TRD (time of Re-depletion) model ages, which provide minimum estimates for the timing of melt depletion, ranging from 2.4 to 0.3 Ga, with a main mode spanning from 2.4 to 1.7 Ga. No Archean ages were recorded. This finding and the complex nature of events affecting this terrane from the Archean through the Palaeoproterozoic provide evidence that the majority of the lithospheric mantle was depleted and stabilised in the Palaeoproterozoic, significantly later than the Archean crust. The timing of the dominant lithosphere formation is linked to rifting (~2.2 Ga - 2.0 Ga), and subsequent collision (1.9-1.8 Ga) of the Superior and Hearne craton during the Wilson cycle of the Trans Hudson Orogen.

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