STRUCTURAL CONSTRAINTS ON THE TECTONIC EVOLUTION OF A LATE ARCHEAN GREENSTONE-BELT IN THE NORTHEASTERN SUPERIOR PROVINCE, NORTHERN QUEBEC (CANADA)

A detailed structural analysis shows that the Vizien greenstone belt o f northeastern Superior Province records five generations (G(1) to G(5 )) of ductile deformation, as well as brittle faulting. G(1) is indica ted by the local presence of a pre-G(2) foliation and is interpreted t o be related to thrusting. G(2) is responsible for the main penetrativ e foliation (S-2), axial-planar to tight to isoclinal F-2 folds and su bparallel to major boundaries between lithotectonic panels. It is conc entrated in a thrust with sense of shear opposite to that interpreted for G(1), F-3 and F-4 folds are open to tight, with NNW-SSE- and E-W-t rending axial surfaces, respectively. They warp the S-2 foliation and major panel boundaries and dominate the map pattern. G(5) is associate d with dextral transcurrent movement along a NNW-SSE-trending shear zo ne. Through understanding of its geometry and deformation history, the Vizien belt has been unfolded into its much simpler pre-G(3) geometry . This greatly helps in the investigation of relationships between the different panels (proposed terranes), their tectonic settings and the kinematics of panel amalgamation. The structural study, in concert wi th geological and geochemical work, leads to a tectonic model for the evolution of the greenstone belt, which involves subduction of oceanic lithosphere and continental are volcanism at similar to 2724 Ma, intr a-arc rifting at similar to 2722 Ma, and collision between similar to 2718 and similar to 2693 Ma with associated obduction of oceanic plate au crust, formation of melange and deposition in a possible foreland b asin. The G(1) and G(2) deformations are interpreted to: be related to synthetic thrusting and back thrusting, respectively, during the coll ision.