Deformation at an Archean subprovince boundary, northern Minnesota

Structural analysis in the northern margin of the Quetico subprovince (part of the Archean Superior Province of the Canadian Shield) in Minnesota reveals that the main deformation involved polyphase folding (F₁ recumbent and nappe-like, and F₂ upright, east-west trending, and tight to isoclinal) during regional ductile transpression and amphibolite-facies metamorphism. A younger deformation, developed during the latter stages of regional transpression, resulted in the generation of localized ultraphyllonites along the steeply dipping Rainy Lake-Seine River fault (RLSRF), the major fault separating the Quetico subprovince from the Rainy Lake wrench zone. Tectonic settings for the RLSRF include 1) a suture between distinct lithotectonic terranes, or 2) a zone of localization of deformation within the northern margin of the Quetico subprovince following collision between the Quetico and Wabigoon terranes. -from Authors