Dome-and-keel and linear accretionary architectures in the eastern Wabigoon superterrane, Canada: seismic profiling, magnetotelluric modelling, and gold endowment

Tectonic processes control the formation of orogenic gold deposits. In Archean greenstone belts, both vertical and horizontal tectonic processes may have contributed to the formation of the deposits. Their relative contributions are evaluated in the Eastern Wabigoon terrane of the western Superior craton, Canada, where both vertical and horizontal tectonic processes operated during the Neoarchean Shebandowanian Orogeny. In the centre of the terrane, the Onaman–Tashota belt developed a dome-and-keel architecture during vertical tectonism, whereas along the southern margin of the terrane, the Beardmore–Geraldton belt acquired a linear accretionary architecture during horizontal tectonism. Orogenic gold deposits formed in deformation zones during doming in the Onaman–Tashota belt and along thrust faults during accretion in the Beardmore–Geraldton belt. A new Metal Earth seismic and magnetotelluric section across the two belts suggest that accretionary structures present in the Neoarchean rocks of the Beardmore–Geraldton belt are also present in the Mesoarchean basement rocks underlying the Mesoarchean to Neoarchean Onaman–Tashota belt. However, only in the Beardmore–Geraldton belt, where horizontal tectonic processes dominated, do they spatially coincide with gold deposits and conductors extending from the mid-crust to surface. These conductors represent deeply penetrating structure that channeled the upward flow of hydrothermal fluids. The presence of these structures in the Beardmore–Geraldton belt and their reactivation as transcurrent shear zones during subsequent gold mineralizing events explain the large difference in gold endowment between the two belts with over 4 million ounces of gold produced in the Beardmore–Geraldton belt compare to less than 100 000 ounces of gold in the Onaman–Tashota belt.