The evolution of the late Paleoproterozoic Wernecke Supergroup, Wernecke Mountains, Yukon, from sedimentation to deformation

The Wernecke Supergroup of Yukon is a metasedimentary succession deposited between ca. 1.66 and 1.60 Ga on the northwestern margin of ancestral North America (Laurentia). U-Pb detrital zircon geochronology, major and trace element geochemistry, and Nd isotope geochemistry reveal that the clastic sediments were derived mostly from collisional orogens that resulted from the amalgamation of Laurentia during Paleoproterozoic. Some detritus may have originated from non-North-American terranes such as eastern Australia or exotic arc terranes. Deposition of the Wernecke Supergroup occurred in a passive margin which resulted from the initial breakup of the supercontinent Columbia, and involved separation of northwestern Laurentia from adjacent continents, probably eastern Australia and the Yangtze craton of South China. This reconstruction is similar to the SWEAT configuration proposed for the Neoproterozoic supercontinent Rodinia. The Wernecke Supergroup was deformed at ca. 1.60 Ga by the Racklan orogeny which was accompanied by greenschist facies metamorphism, exhumation and erosion of the Wernecke Supergroup, and obduction of an exotic terrane, named Bonnetia, which was previously located offshore from the northwestern margin of Laurentia. The final stage of the Racklan orogeny was the result of the collision between eastern Australia and western Laurentia in another SWEAT-like configuration. The Racklan orogeny is regarded as part of a long orogenic belt which flanked the supercontinent Columbia at 1.65-1.60 Ga. This belt was developed on Amazonia, Baltica, eastern and southern Laurentia, East Antarctica, East Australia, and northwestern Laurentia. Following Racklan orogeny, a set of hydrothermal fluids intruded and brecciated the Wernecke Supergroup and caused collapse of fragments of the tectonically overlying Bonnetia. This hydrothermal event was responsible for the emplacement of iron oxide-copper-gold (IOCG) mineralization in the area, and is similar in age, and is possibly related to, IOCG deposits located in east Australia and South China.