Late Nagssugtoqidian stress rientation derived from deformed granodiorite dykes north of Holsteinsborg, West Greenland

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Abstract
A suite of granodiorite dykes, of varied but non-random orientation, cuts basement gneisses in a 15 km x 8 km coastal strip around lat. 67°N in central West Greenland. The dykes which were metamorphosed in the granulite facies have been deformed by simple shear and vary from apparently unstrained to highly strained. The deformation occurred during a late stage of Nagssugtoqidian deformation (Lower Proterozoic). The orientation of the principal stress planes and of the σ 1 axis are determined on a best-fit basis from the change in sense of shear direction observed in the horizontal and in the vertical plane. The positions of the σ 2 and σ 3 axes are determined by a method involving a comparison of the observed shear directions with those predicted from a model stress system with known σ 1 and σ 2 = σ 3 . This stress model gives a σ 1 with a plunge of 28° on a bearing of 161°, a horizontal σ 3 and a steep σ 2 . This result is consistent with other more approximate estimates of the Nagssugtoqidian stress orientation near the Nagssugtoqidian front in W Greenland.

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