Lu-Hf and Re-Os systematics of peridotite xenoliths from Spitsbergen, western Svalbard: Implications for mantle-crust coupling

The timing of sub-continental lithospheric mantle (SCLM) differentiation beneath Spitsbergen, western Svalbard, has been determined with spinel peridotite xenoliths using two complementary isotopic systems: Lu-Hf and Re-Os. The whole-rock Re-Os systematics (Re-Os errorchron, aluminochron, and Re-depletion age) define Paleoproterozoic/Neoarchean ages for isolation of the studied peridotites from the convecting mantle. We note that the age is independently supported by the Lu-Hf errorchron for the peridotite clinopyroxene grains, and average degree of melt depletion recorded in the samples. The obtained ages are indistinguishable from the oldest crustal ages reported in western Spitsbergen, implying that the mantle lithosphere in this area was stabilized at the same time as formation of the overlying crust. Our data suggest that the Spitsbergen lithosphere is unlikely to have undergone bulk lithospheric delamination since the tectonic transition from transpressional to transtensional which commenced in the Paleocene. We thus discount the delaminated and reactivated SCLM as a potential source for the Dupal-like enriched components in the Arctic upper mantle suggested by other studies. (C) 2010 Elsevier B.V. All rights reserved.