Abstract

The Kisseynew metasedimentary gneiss belt (Kisseynew domain), which represents one of the most extensive tectonic segments of the Paleoproterozoic Trans-Hudson orogen in north-central Canada, initially developed in a back-arc setting. It comprises turbidites and continental sandstones, both of which are interlayered with rare volcanic rocks and intruded by plutons. The ages of detrital zircons and crosscutting plutons constrain turbidite sedimentation to 1.855–1.841 Ga, postdating early deformation and metamorphism associated with arc-arc and arc-continent collisions affecting much of the Trans-Hudson orogen. These turbidites are interpreted to have been deposited in a back-arc basin behind a retreating subduction boundary. The Kisseynew domain and its southern flank are marked by 1.84–1.83 Ga magmatic rocks that may be related to subduction of back-arc basin oceanic crust. Collapse of the Kisseynew “basin” by ductile fold-and-thrust deformation began during 1.84–1.83 Ga magmatism and continued through peak metamorphism at ca. 1.820–1.805 Ga. The result was that the high-grade core of the Kisseynew domain was structurally emplaced over adjacent low-grade terranes. The regionally extensive high-temperature and low-pressure metamorphism that characterizes the Kisseynew domain is best explained by thickening and thermal relaxation of basin-fill rocks marked by a geotherm elevated by 1.84–1.83 Ga magmatism.

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