On Archean craton growth and stabilisation: Insights from lithospheric resistivity structure of the Superior Province

Abstract

The nature of lithospheric evolution and style of the driving tectonic processes during the growth and stabilisation of continental crust in the Archean remain enigmatic. The hotter, rheologically weak Archean crust would be unable to support thick orogens. Thus, gravitational collapse likely occurred when continental fragments became overthickened and/or when far-field stresses were relieved during the terminal stages of orogenesis. 3D magnetotelluric resistivity models of the Archean Superior Province, reveal the presence of low resistivity zones in the mid-lower crust that reflect a protracted history of magmatic-hydrothermal activity contemporaneous with construction and collapse. These include sub-vertical zones of low resistivity in the mid-upper crust, inferred to represent corridors of paleo-fluid flow along crustal-scale structural networks developed in response to terrane amalgamations. Subsequent orogenic collapse resulted in widespread lateral flow within the lower crust accommodated by sub-horizontal shear zones and included magmatic refertilisation. Thus, the preserved low-resistivity anomalies in the mid-lower crust represent an amalgamation of magmatic-hydrothermal and deformational processes that occurred during construction, peak orogenesis, and collapse in the Archean.