Metamorphic evolution of the Great Slave Lake shear zone

The Palaeoproterozoic Great Slave Lake shear zone (GSLsz) is a crustal-scale strike-slip structure, with total length of >1,000 km and width ~25 km, that separates the Archean Rae cratons. range metamorphic rocks now exposed at surface encompasses granulite facies mylonite through to lower-greenschist ultramylonite cataclasite, providing potential type example fault-zone structure in middle lower crust. However, evolution units remains poorly quantified, hindering detailed structural tectonic interpretations. Here, we use phase equilibria modelling thermobarometry determine conditions recorded by pelitic, mafic felsic GSLsz mylonites. Samples from entire granulite–greenschist preserve evidence for nested clockwise pressure–temperature paths are consistent single orogenic cycle. Our findings indicate northern margin underwent pervasive crustal thickening peak pressures metasedimentary reaching ~1.1 GPa. thermal gradient onset was ~650°C/GPa, whereas final stages equilibrium fine-grained matrix minerals all samples collectively define field ~1,000°C/GPa. Deformation microstructures main dextral having been synchronous or following metamorphism. history metamorphism exhumation Sibson–Scholz model zones, narrowing deforming progressive overprinting higher-grade assemblages during shallower levels.