Linking the Palaeoproterozoic Nagssugtoqidian and Rinkian orogens through the Disko Bugt region of West Greenland

The parallel Trans-Hudson-aged Nagssugtoqidian Orogen and Rinkian Fold Belt of West Greenland have long been considered distinct orogenic belts separated by a zone of low or no Palaeoproterozoic strain in the intervening Disko Bugt region. New U-Pb geochronology confirms the continuity of Palaeoproterozoic deformation and metamorphism through this region, thereby directly linking the Nagssugtoqidian Orogen and Rinkian Fold Belt. Furthermore, two newly identified Archaean blocks in this region are interpreted to represent the southern and northern extensions of the Rae and North Atlantic cratons, respectively. Their boundary comprises a 15 km wide belt of distributed, NW-vergent ductile thrusts that deform ultramafic pods and is interpreted to represent the main collisional suture of a single, variably exhumed, > 1100 km wide Nagssugtoqidian-Rinkian orogenic system. We conclude that Palaeoproterozoic convergence of a northern Archaean craton carried a south-facing passive margin sedimentary sequence (Karrat Group) towards a south-dipping subduction zone along the North Atlantic Craton. Terminal collision created a high-grade core centred on the magmatic arc of the central Nagssugtoqidian Orogen and a NW-vergent fold and thrust belt in the Rinkian Fold Belt.