Mehdi Tavakoli Yaraki, PhD

M. Tavakoli Yaraki¹, B. Lafrance¹, R. Sherlock¹, M. Naghizadeh¹, R. Vayavur^1
1Mineral Exploration Research Centre, Harquail School of Earth Sciences, Laurentian University, Sudbury, Ontario, Canada

The Atikokan area, which is located 175 km west of Thunder Bay, Ontario, consists of Mesoarchean rocks (greenstone belts, and TTGs) of the Marmion Terrane of the Wabigoon subprovince and Neoarchean metasedimentary rocks of the Quetico subprovince to the south. The east-west-trending Quetico Fault straddles the contact between the two subprovinces. The Quetico Fault is a major Neoarchean dextral strike-slip fault with a strike length of over 400 km. Numerous mineral prospects (e.g., gold, copper, and zinc in Mine Centre) occur along the Quetico Fault, which structurally controlled the formation of these mineralized prospects. Although the Quetico Fault is locally well exposed at the surface, and its surface kinematic history is well known through previous structural field studies, its subsurface geometry is unknown. A new Metal Earth seismic and magnetotelluric transect, along with previous Lithoprobe seismic profiles, suggests that the fault originated as a low-angle thrust fault during duplex formation and south-verging imbrication of the lower crust of the Wabigoon and Quetico subprovinces. The fault formed as a deep-seated low-angle ductile thrust zone in the lower crust which steepens upwards to sub-vertical dip near the surface. Detailed surface structural mapping confirms that the fault then evolved into a dextral transpressional zone during a subsequent deformation event. Our study presents new insights into the structural evolution of Archean fault systems and advanced our understanding of the tectonic processes in the western Superior Province.