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TitreA Re-Os isotope and PGE study of kimberlite-derived peridotite xenoliths from Somerset Island and a comparison to the Slave and Kaapvaal cratons
AuteurIrvine, G J; Pearson, D G; Kjarsgaard, B A; Carlson, R W; Kopylova, M G; Dreibus, G
SourceA tale of two cratons: the Slave-Kaapvaal workshop; par Jones, A G (éd.); Carlson, R W (éd.); Grutter, H (éd.); Lithos vol. 71, issue 2-4, 2003 p. 461-488,
LiensAbstract - Résumé
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 2002134
ÉditeurElsevier BV
RéunionThe Slave-Kaapvaal Workshop; Merrickville, Ontario; CA; Septembre 5-9, 2001
Documentpublication en série
Mediapapier; en ligne; numérique
SNRC58B; 58C; 58D; 58F
Lat/Long OENS -96.6000 -88.6333 74.3500 71.7667
Sujetsplatine; géochimie du platine; osmium; iridium; palladium; manteau terrestre; péridotites; kimberlites; craton; magmatisme; croûte continentale; xénolites; Archéen; etudes isotopiques; géochimie; géochronologie; minéraux métalliques; minéralogie; géologie structurale; pétrologie ignée et métamorphique; Mésozoïque; Crétacé; Protérozoïque
Illustrationslocation maps; geological sketch maps; bar graphs; tables; formulae; graphs; geochemical plots
Résumé(disponible en anglais seulement)
The concentrations of platinum-group elements (PGE; Os, Ir, Ru, Pd and Pt) and Re, and the Os isotopic compositions were determined for 33 lithospheric mantle peridotite xenoliths from the Somerset Island kimberlite field. The Os isotopic compositions are exclusively less radiogenic than estimates of bulk-earth (187Os/188Os as low as 0.1084) and require a longterm evolution in a low Re-Os environment. Re depletion model ages (TRD) indicate that the cratonic lithosphere of Somerset Island stabilised by at least 2.8 Ga, i.e. in the Neoarchean and survived into the Mesozoic to be sampled by Cretaceous kimberlite magmatism. An Archean origin also is supported by thermobarometry (Archean lithospheric keels are characterised by >150 km thick lithosphere), modal mineralogy and mineral chemistry observations. The oldest ages recorded in the lithospheric mantle beneath Somerset Island are younger than the Mesoarchean (>3 Ga) ages recorded in the Slave craton lithospheric mantle to the southwest [Irvine, G.J., et al., 1999. Age of the lithospheric mantle beneath and around the Slave craton: a Rhenium-Osmium isotopic study of peridotite xenoliths from the Jericho and Somerset Island kimberlites. Ninth Annual V.M. Goldschmidt Conf., LPI Cont., 971: 134-135; Irvine, G.J., et al., 2001. The age of two cratons: a PGE and Os- Isotopic study of peridotite xenoliths from the Jericho kimberlite (Slave craton) and the Somerset Island kimberlite field (Churchill Province). The Slave-Kaapvaal Workshop, Merrickville, Ontario, Canada]. Younger, Paleoproterozoic, TRD model ages for Somerset Island samples are generally interpreted as the result of open system behaviour during metasomatic and/or magmatic processes, with possibly the addition of new lithospheric material during tectono-thermal events related to the Taltson-Thelon orogen. PGE patterns highly depleted in Pt and Pd generally correspond to older Archean TRD model ages indicating closed system behaviour since the time of initial melt extraction. Younger Proterozoic TRD model ages generally correspond to more complex PGE patterns, indicating open system behaviour with possible sulfide or melt addition. There is no correlation between the age of the lithosphere and depth, at Somerset Island.