A geological investigation of the Thluicho Lake Group, southwestern Rae Province, Saskatchewan, Canada.

摘要

The Thluicho Lake Group is a middle Paleoproterozoic, greenschist-facies clastic succession located in the Zemlak Domain of the southwestern Rae Province. It consists of a single, upward fining succession of conglomerate, pebbly sandstone, sandstone and argillite. Two informal formations are proposed: the Powder Lake formation, which comprises the 'Gulo Lake' conglomerate, the 'Camel Lake' pebbly sandstone, and the 'Wellington Lake' sandstone members, and the Camsell Portage formation, which comprises the 'Falls' pebbly sandstone to siltstone, the 'Waterloo Lake' rhythmic sandstone and argillite, and the 'Slate Island' argillite members. The Powder Lake formation was deposited in an alluvial environment dominated by alluvial fan to braid plain deposits, whereas deposition of the Camsell Portage formation occurred within subaqueous fan-delta to lacustrine environments. It is interpreted that the Thluicho Lake Group sediments were deposited within an intermontane basin created by the uplift and erosion of mountains formed during the Taltson-Thelon orogeny.; The contact between the basal conglomerate and mylonitic basement, though locally strained, is in certain exposures an intact angular unconformity. Three phases of folding have affected the Thluicho Lake Group, including: (1) tight to isoclinal, east to southeast-trending F1 folds; (2) steeply inclined, northeast-trending, open to close F2 folds; and (3) upright, north-trending, open F3 folds. Superposed fold interference between F1 and F2 folds has resulted in a modified type 2, dome-crescent-mushroom pattern. The regional fold pattern is further complicated by brittle faults and fractures. Investigation of the Ellis Bay formation, now termed the Ellis Bay breccia, has shown that it is a complex breccia system located in proximity to major fault zones in the study area, and may be a sedimentary diatreme breccia complex.; Deposition of the Thluicho Lake Group, together with the first two phases of folding, is constrained between 1.93 Ga, an upper amphibolite-facies metamorphic event that pre-dated deposition of the Thluicho Lake Group, and 1.82 Ga, which represents the age of diabase dyke intrusion and deposition of the unconformably overlying Martin Group. The orientation of F1 folds lends further support to recent interpretations that the Taltson Magmatic Zone was initially east-southeast trending. F2 folding was related to activity along the Snowbird Tectonic Zone to the east, and/or the early collision of the Slave and Rae cratons, as well as accretionary events to the west of the Wopmay Orogen. F3 folds formed in response to late Slave craton indentation to the west and the terminal collision of the Trans-Hudson Orogen to the east.