Andean-type, bivergent crustal shortening in the Rinkian Orogen; new constraints on the tectonic evolution of Laurentia-West Greenland in the Paleoproterozoic

The "Rinkian belt" of West Greenland is a metamorphic terrain of Paleoproterozoic age comprising: (1) the north Rinkian fold-thrust belt (FTB)-a pro- or fore-arc domain, highly deformed and metamorphosed with widespread anatexis; (2) the Proven Igneous Complex-a magmatic arc characterized by hypersthene granitic rocks ("charnockites"); (3) the south Rinkian FTB - an inverted back-arc basin; and (4) a continental margin or foreland. Recognition of this tectonic architecture demonstrates that the "Rinkian" is a bona fide orogenic belt - the Rinkian orogen - and not simply the imbricated lower plate of the Nagssugtoqidian orogen. Arc plutons of the Proven Igneous Complex were emplaced into the Karrat Group at ca. 1.90-1.85 Ga, dividing a back arc basin into pro- and retro-arc domains. In the former-the north Rinkian FTB-WSW-directed thrusting (deformation events D1-D2) and high-grade metamorphism were taking place by ca. 1.875 Ga and were continuous through ca. 1.850 Ga with a peak temperature at ca. 1.830 Ma accompanied by anatexis in the Karrat Group and lower units of the Proven Igneous Complex. In the retro-arc domain - the south Rinkian FTB - thrusting to the E (D1) began at ca. 1.870 Ma followed by thrusting to the W (D2) at ca. 1.830-1.820 Ga with displacement focused into a major high-temperature ductile shear zone which carried the Proven Igneous Complex in the hanging wall of an Andean-type, crustal-scale, "pop-up" structure. High-temperature deformation continued during D3 when the pro-arc, arc, and retro-arc domains were shortened by bivergent detachment folding and thrusting at ca. 1.820-1.810 Ga.