Age and origin of the Jan Lake Complex: a glimpse at the buried Archean craton of the Trans-Hudson Orogen

Abstract

The largely buried Sask Craton is a continental fragment or microcontinent that collided with and underthrust the Paleoproterozoic Flin Flon - Glennie protocontinent along the Pelican Décollement Zone at 1840-1830 Ma. Rocks of the Sask Craton are exposed in three tectonic windows. Those of the Pelican Window have been named the Jan Lake Complex and comprise [Formula: see text] 2960 Ma arc-derived leucocratic orthogneisses, migmatitic paragneisses, and a tholeiitic, within-plate igneous suite comprising 2488 Ma dioritic to gabbroic rocks and 2450 Ma enderbitic and charnockitic rocks including the Sahli Granite. Ages of ca. 2450 Ma are also common from the other two tectonic windows to the Sask Craton, suggesting that emplacement of the igneous suite was widespread and perhaps part of the coeval Matachewan Igneous Event. The absence of rocks in the [Formula: see text] 2960 and ca. 2450 Ma age ranges on both the adjacent Superior and Rae-Hearne cratonic margins makes it improbable that the Sask Craton was derived by simple fragmentation without large-scale tectonic transport. The overthrust Paleoproterozoic rocks represent a high-grade northwestern extension of the Flin Flon volcanic belt and include 1856 Ma leucotonalite and 1843 Ma quartz monzodiorite. An 1830 Ma suite of homogeneous, calc-alkaline enderbitic rocks, which intrude Burntwood semipelitic migmatites throughout the Kisseynew Domain, has also been emplaced in mylonites of the Pelican Décollement Zone. Zircon and monazite ages in the 1812-1803 Ma range record a high-grade metamorphic event that resulted from collision between the Sask Craton and Flin Flon - Glennie Complex.