Kinematics and Timing of Shear Zones in the Nonacho Lake Area: Preliminary Results



Rebecca Canam –



R. Canam – Simon Fraser University, Burnaby, BC, Canada
D. Gibson – Simon Fraser University, Burnaby, BC, Canada
E. Martel – Northwest Territories Geological Survey, Yellowknife, NT, Canada
D. Kellett – Geological Survey of Canada, Dartmouth, NS, Canada



The Nonacho Lake area located along the western margin of the Rae craton in the southeastern Northwest Territories consists of the ca. 1.91-1.82 Ga siliciclastic Nonacho Group interpreted to have been deposited in a fault-controlled basin unconformably overlying Archean to Paleoproterozoic granitic and gneissic basement rocks. Detailed mapping during the 2019 and 2020 field seasons revealed two major sinistral, southwest-trending, steeply-dipping, ductile to brittle shear zones, and several minor steeply-dipping shear zones in the Nonacho Lake area. The major shear zones flank the western and eastern edges of the Nonacho basin with shear strain accommodated in the Hjalmar, Chief Nataway, Tronka Chua and Thekulthili formations of the Nonacho Group and within Nonacho basement units. Preliminary LA-ICPMS analyses of zircon in a syn-tectonic granitic dyke suggest the greenschist-facies fabric associated with the sinistral shearing of the Nonacho Group occurred at ca. 1.85 Ga. Future work will include: 1) 40Ar/39Ar thermochronology to constrain timing of basement uplifts and delineate crustal-scale boundaries; 2) U-Pb titanite geochronology to constrain timing of deformation and shear zone development in the Nonacho basement units. 

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