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 Paleopro-terozoic 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 oro-genic 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 detach-ment folding and thrusting at ca. 1.820- 1.810 Ga.