The Laurentia – West Greenland connection at 1.9 Ga: New insights from the Rinkian fold belt

Abstract

U-Pb data from the Rinkian fold Belt, western Greenland, provide new constraints on provenance and timing of deposition of the Karrat Group, the emplacement interval of the Prøven Igneous Complex, and the tectonic setting of west Greenland during the interval 2.03–1.83Ga. U-Pb detrital data establish the entire Karrat Group metasedimentary succession as Paleoproterozoic in age, initiated after ca. 2029Ma (Qeqertarssuaq Formation), with deeper water deposition after 1953±31Ma and 1905±20Ma (Nûkavsak Formation). The detrital age profiles highlight a profound change in source region after ca. 1.95Ga that we attribute to thickening, uplift, and exhumation related to collision of a juvenile magmatic arc with the northwest margin of Rae craton at ca. 1.97–1.95Ga (Thelon Orogen). Accordingly, the Karrat Group is viewed as having initiated as an extensional rift basin(s) that received ca. 3.00–2.95Ga detritus from local basement sources, and which evolved into a deeper water foreland-basin succession derived from the north. This foreland basin was intruded by the Prøven Igneous Complex, for which new U-Pb data establish emplacement between 1.90 and 1.87Ga in a within-(Rae) plate setting. Prøven plutonism is coeval with lower-plate mantle magmatism elsewhere across NE Laurentia which may have been triggered by asthenospheric thinning due to plume-induced extension of lower-plate Rae craton at 1.95–1.92Ga. Our data refute a direct link between the Prøven Igneous Complex and the voluminous 1.86–1.845Ga Cumberland Batholith, Baffin Island, long considered its counterpart.