• Main Authors: William E. Glassley, John A. Korstgård, Kai Sørensen
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Greenland; Nordre Strømfjord; Sion; Nordre strømfjord
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.517.4094; http://www.geus.dk/publications/bull/nr13/nr13_p49-52.pdf

The Nordre Strømfjord shear zone is a 1.8 Ga zone of large-scale, transcurrent and sinistral ductile shear (Sørensen et al. 2006) within the Nagssugtoqidian Mobile Belt (NMB) of central West Greenland. It has been hypothesised that the NMB is a suture between two Archaean continental masses (Kalsbeek et al. 1987). During field work in 2005 along the Nordre Strømfjord shear zone in the fjord Ataneq (Fig. 1), some unusual rock types were discovered that preserve evi-dence of magmatic and metamorphic processes not previ-ously reported in the area. These observations include the first indication of high-pressure (HP) metamorphism in West Greenland and the first reported occurrence of a cumulate of giant orthopyroxene. The tectonic telescoping of these fea-tures together within the Nordre Strømfjord shear zone has important implications for reconstructing the Palaeopro-terozoic history of this region, and provides evidence that processes typical of Phanerozoic continent–continent colli-sion zones (e.g. the Caledonian and Alpine systems) operated at least as far back as 1.8 Ga ago. High-pressure enclave On the north side of inner Ataneq fjord an approximately 1.2 m wide and 4 m long lens of ultramafic rock occurs within strongly foliated garnet-sillimanite gneisses and schists, and garnet-bearing calc-silicate rock (Fig. 2). The pale yellowish green, ultramafic rock is moderately foliated with its long axis parallel to the fabric in the enclosing gneisses. This core of the