Tectonics of the Paleoproterozoic Rinkian orogen, central West Greenland

A new tectonic model is presented to ex-plain the tectono-stratigraphic evolution of the Paleoproterozoic Karrat Group in cen-tral West Greenland and the polyphase de-formation, magmatism, and metamorphism of the Rinkian orogen. Sedimentation of the Karrat Group initiated after ca. 2000 Ma in an intracratonic rift basin with basal quartz-ites overlying Archean gneisses of the Rae craton. Rift-related alkaline volcanic rocks and synrift siliciclastic sediments were de-posited in the north while an evaporite-car-bonate platform developed in the south. The rift basin evolved to a back-arc basin, with associated subalkaline volcanic rocks, con-comitant with the intrusion of arc-related granitoids of the Proven igneous complex along the basal contact of the Karrat Group between 1900 Ma and 1850 Ma. The Karrat Group and magmatic arc rocks underwent metamorphism ca. 1830-1800 Ma during the collisional phase of the Rinkian orogeny. The metamorphic grade of the Karrat Group in-creases from greenschist facies in the south to granulite facies in the north, where it is marked by migmatization and emplacement of S-type leucogranites. Extensive east-south-eastward thrust emplacement and fold ver-gence characterize the Rinkian orogen south of the Proven igneous complex magmatic arc, where the arc-continent collision is es-tablished along a top-to-the-ESE shear zone postdating the Rinkian metamorphism. In summary, the Karrat Basin developed on the upper plate above eastward-dipping subduc-tion and, together with the Rinkian orogen, represents the result of arc-continent colli-sion that initiated the structuring of a back-subduction tons. formed tinent et such were tion, final 2001; oid fin et subducting craton, ault et tion the direction arc fold-and-thrust system antithetic to the subduction system.