The Reorientation of the Kangâmiut Dike Swarm, West Greenland

Abstract

The Nagssugtoqidian belt in West Greenland is formed mainly of Archaean rocks which were strongly reworked during the early Proterozoic. Investigation of the southern boundary region has resulted in a model for the tectonic reworking based on the geometry of homogeneous simple shear deformation. Two differently oriented swarms of mainly pre-kinematic dikes are used as strain indicators at the deformation boundary. Gneiss tectonite fabrics have been used to determine that the shear plane dips northwest at 20–40° and that the shear direction along this plane is towards the southeast. The average amount of simple shear strain (S = 6) has been determined from the degree of dike reorientation. This mechanism has resulted in a ductile overthrusting of the reworked rocks over the Archaean foreland, giving a crustal shortening of ca. 66%. The area investigated represents a deep tectonic level. At higher levels ductile deformation would be expected to give way to thrust and fold nappe development. The displacements demonstrated are those which might be expected in the deformed margins of colliding continental plates.

Integration of Vessel-Based Hyperspectral Scanning and 3D-Photogrammetry for Mobile Mapping of Steep Coastal Cliffs in the Arctic

“…The steep coastal cliffs, which have been scanned in this area (Figure 1b), are located south of the borderland between the late Nagssugtoqidian Orogen and the early Kangâmiut Complex [50]. The Kangâmiut Complex comprises undeformed mafic dyke swarms emplaced into the high-grade gneisses of the Archaean craton of southwest Greenland and is characterized by hornblende as the dominant primary ferromagnesian mineral [51][52][53][54]. The host rocks for the dyke swarm are mainly tonalitic and granodioritic gneisses.…”

Correlation of Archaean and Palaeoproterozoic units between northeastern Canada and western Greenland: constraining the pre-collisional upper plate accretionary history of the Trans-Hudson orogen

“…The orthogneiss are generally 2.87-2.81 Ga in age, with the plutonic protoliths deformed and metamorphosed between 2.81 and 2.72 Ga, immediately after their emplacement (Kalsbeek & Nutman 1996;. The orthogneiss are cut by several sets of mafic dykes, the most voluminous of which is the north-south-to NE-SW-trending, 2.05 -2.04 Ga Kangâmiut dyke swarm (Windley 1970;Escher et al 1975Escher et al , 1976aKorstgård 1979;Bridgwater et al 1995;Cadman et al 2001;Mayborn & Lesher 2006). The Kangâmiut dyke swarm, which extends from the Archaean foreland into the centre of the orogen, becomes reworked across an abrupt transition at the southern Nagssugtoqidian front (Fig.…”

O enxame de diques de anfibolito do Cráton São Francisco meridional

“…INTRODUÇÃO Diversos pesquisadores (Escher et al 1975, Wilson et al 1985, Park & Tarney, 1987, Cadman et al 1990) têm observado que muitos enxames de diques máfi cos parecem estar aproximadamente paralelos a grandes zonas de cisalhamento em regime de transcorrência, estando os diques associados e afetados por estas zonas. Park & Tarney (op.cit.)…”