The Nagssugtoqidian Orogen of West Greenland represents a belt of Palaeoproterozoic deformation and metamorphism between the North Atlantic Craton of South Greenland and a northern, lesser known continental segment that includes the Rinkian Orogen. First-order observations are interpreted to support a cycle of separation, convergence, and eventual collision of two continental masses. The emplacement of the Kangâmiut dyke swarm marked the onset of continental breakup at ca. 2040 Ma, and sedimentary basins formed between ca. 1950 and 1920 Ma. Subsequent convergence and consumption of an oceanic plate caused arc magmatism at 1920-1870 Ma. Granulite-facies peak metamorphism at 1860-1840 Ma in the centre of the orogen is related to crustal thickening by WNW-directed thrusting. Large-scale, upright folding with an east-west trend was ongoing by 1825 Ma. Sinistral strike-slip movement was concentrated along steeply dipping limbs of these large-scale folds and formed orogen-scale steep belts at ca. 1775 Ma. Close similarities between the northern and southern foreland suggest that the two cratons likely originated from one continuous continental block. Temporal and kinematic correlation of these events with adjoining orogens in Canada and Greenland shows close genetic links. The Nagssugtoqidian Orogen of West Greenland continues eastwards beneath the Greenland Ice cap to the Eastern Nagssugtoqidian belt of East Greenland (a.k.a. the Ammassalik belt). The Torngat Orogen of eastern Canada developed simultaneous with the Nagssugtoqidian Orogen with a kinematic compatibility suggesting that the two orogens formed on the west and north flanks, respectively, of a curved leading continental margin of an indenting North Atlantic Craton.
- Programområde 4: Mineralske råstoffer