Evolution of the Snow Lake portion of the Palaeoproterozoic Flin Flon and Kisseynew belts, Trans-Hudson Orogen, Manitoba, Canada

Abstract

Understanding growth of early Precambrian crust requires knowledge of the evolution of granite-greenstone and metasedimentary belts, two of the fundamental building blocks of early Precambrian cratons. UPb geochronologic data from the Snow Lake area, which straddles the Flin Flon granite-greenstone and Kisseynew metasedimentary belts of the Trans-Hudson Orogen, documents a 60–70 Ma period of Palaeoproterozoic crust formation from inception of these belts in ocean basins through their eventual structural telescoping during ocean basin consumption and collision with bounding Archaean cratons. Earliest volcanic and plutonic rocks of the Flin Flon granite-greenstone terrane at Snow Lake formed ∼1.89 Ga, mainly in a juvenile oceanic arc tectonic setting. Sedimentary rocks of the Kisseynew belt, previously thought to be contemporaneous with Snow Lake area arc volcanism, are up to 30–50 Ma younger (∼1.86-1.84 Ga) and postdate deformation associated with ∼1.88-1.87 Ga arc-arc collisions and ∼1.87-1.84 Ga calc-alkaline plutonism that affected much of the western Flin Flon belt. Deformation at Snow Lake occurred during two widely spaced episodes, both of which effect the post 1.86-1.84 Ga turbidite sequence and, thus, postdate 1.88-1.87 Ga intraoceanic accretion in the western Flin Flon Belt. The older deformational episode involved isoclinal folding formed during ∼1.84 Ga convergence of the Kisseynew and Flin Flon belts and thrusting of Kisseynew sedimentary lithologies southwards onto the Flin Flon volcanic rocks. The younger deformational episode occurred 15–25 Ma later and involved further folding and southwest thrusting, accompanied by a ∼1.81 Ga high grade thermal metamorphic episode, centred in the Kisseynew Belt. Only minor increase of crustal material, in the form of late intrusions, were added following this episode.