Metamorphism of the Kisseynew gneisses and related rocks of the Reindeer Zone, Trans-Hudson Orogen, northern Saskatchewan

Abstract

In the Reindeer Zone of Saskatchewan, the mostly metasedimentary Kisseynew gneiss crops out in a 300 km wide belt extending from the Tabbernor Fault to the Manitoba border. Metamorphic grade varies from middle amphibolite to granulite facies. Associated with the main Kisseynew gneiss are metasedimentary rocks of the Glennie Domain, Attitti Block, and Hanson Lake Block. Sillimanite is the common aluminosilicate in most parts of the four domains. Andalusite occurs at several places within the southern Glennie Domain, in the southern Hanson Lake Block, and in the northern Flin Flon Belt. Kyanite, appearing relict in many samples, is found in a 10 km × 50 km zone adjacent to the Flin Flon Belt.Most of the regional variation in metamorphic P–T can be explained by postmetamorphic folding and uplift. Peak T varied from less than 600 °C (in the Glennie Domain) to 725 °C. The highest temperatures were recorded near enderbite occurrences at Chicken Lake, 10 km east of Sandy Bay, and along a thermal anticline, extending east-northeast from the Hanson Lake Block, across the Attitti Block. Metamorphic P ranged from less than 4.5 kbar to 10 kbar (1 kbar = 100 MPa). Highest pressures were associated with the uplifted Hanson Lake and Attitti blocks.The Precambrian geology of the Reindeer Zone is characterized by stacked thrust sheets, many of which are separated by originally subhorizontal shear zones. The sheet including the Kisseynew sediments was carried to approximately 20–30 km depth by continental thickening due to the thrusting. Metamorphism did not take place on a normal geotherm: heat for metamorphism was augmented by plutonic heat sources. Late, northeast-plunging folds postdated peak metamorphism and were followed by uplift. If the Kisseynew sediments are metamorphosed equivalents of the Flin Flon Amisk and Missi Groups, a transect from the Flin Flon Belt to the Attitti Block may represent a deformed 20 km section.