Abstract

The southern and western Superior craton of Canada (SWSC) is widely considered to be a tectonic collage accreted from north to south by multiple coeval subduction zones. We propose an alternative non–plate tectonic scenario where SWSC continental fragments are not exotic but derived by partial disaggregation of a heterogeneous older (Superior I) craton in response to a mantle overturn event that started at ca. 2780 Ma. During overturn, radial mantle outflow stretched and disaggregated the lithosphere to create the concentric Neoarchean fabric of the Superior craton, the southern part of which (SWSC) broke up into ribbon continents separated by oceanic tracts. Neoarchean calc-alkaline magmas record interaction between plume-related magma and older crust. A change in the mantle flow field at ca. 2720 Ma caused southward drift of the Northern Superior cratonic block as a result of mantle traction on its lithospheric keel, and SWSC terranes accreted to its leading edge.

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