Abstract
The Storstrømmen shear zone is a NNE-trending belt of steep, heterogeneously deformed gneisses and mylonites, at least 8 km wide, which transects the basement gneiss complexes of the Caledonian fold belt between Dronning Louise Land and Hertugen af Orleans Land. Shear criteria indicate a consistent sinistral sense of displacement parallel to a gently-plunging L-S fabric. Mineral assemblages and fabrics within the mylonites indicate that mylonitisation was initiated under low amphibolite facies conditions and continued within the greenschist facies. The shear zone is reworked by late, steep brittle faults which are associated with cataclasis and local metamorphic retrogression.
Highlights
The Storstrømmen shear zone is aNNE-trending belt of steep, heterogeneously deformed gneisses and mylonites, at least 8 km wide, whieh transeets the basement gneiss eomplexes of the Caledonian fold belt between Dronning Louise Land and Hertugen af Orleans Land
Thc Storstrømmen shear zone (SSZ) has been recognised along the eastern margin ol' Dronning Louise Land (Friderichsen et al, 1990), in north-west Dove Bugt (Chadwick & Friend, 1994) and in eastern Hertugen af Orleans Land (Fig. l; Strachan et al, 1991)
This paper summarises the structural geometry and kinematic evolution ol' the SSZ in eastern Hertugen af Orleans Land, and briefly considers the implications of this data for regional tectonic models
Summary
Most ol' Hertugen af Orleans Land (Fig. l) is underlain by an orthogneiss complex which lies structurally above the Caledonian marginafthrust zone (Strachan et al, 1991). The gneiss complex mainly comprises a heterogeneous series ol' variably banded, migmatitic dioritictonalitic-granodioritic orthogneisses. These typically displayan amphibolite facies metamorphic assemblage of hornblende + biotite + feldspars + quartz + garnet. In south Sønderland and Søndre Mellemland (Fig. 2), the earliest intrusions are swarms of pink, granitic sheets, up to 2 m thick, which carry a penetrative myLonitic fabric. These are apparently post-dated by emplacement ol' white-grey leucocratic granite intrusions, which are mylonitised (Fig. 2). The spatial association of these intrusions with the SSZ may indicate that they were emplaced syn-kinematically during ductile shear
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