Formation of the North Atlantic Craton: Timing and mechanisms constrained from Re–Os isotope and PGE data of peridotite xenoliths from S.W. Greenland

article i nfo In this contribution we present platinum-group element (PGE) abundance and Os isotope data of North Atlantic Craton peridotite xenoliths (n=62) sampled from four major clusters of kimberlite/ultramafi cl amprophyre volcanism in W. Greenland. In addition, we analysed olivine separates from selected peridotites. We find distinct differences in peridotites sampled from the northern (including the reworked Archean Nagssuqtoqidian mobile belt) and southern portions of the W. Greenland fragment of the NAC (WG-NAC). The heavilyserpentinizedharzburgitictoduniticperidotitesfromthenorthernWG-NACaretypicallymarkedbyOsand Ir abundances that are somewhat lower than those of primitive mantle. Pt and Pd abundances are significantly depleted resulting in chondrite-normalized PGE patterns consistent with extensive melt extraction. As a consequence of the meltingprocess,removal of sulphideandpossibly aportionof residual PGE-richalloysislikely. Typically, Os isotopes of these northern samples are unradiogenic (γOs= −14.2 to −6.6, average ca.−9.2), with separated olivines being similar in composition. The unradiogenic Os isotope compositions of the northern peridotites result in TRD erupt model ages clustering between 2.7 and 3.2 and also at ca. 2.0 Gyr. The grouping of the