Oblique Archean subduction: accretion and exhumation of an oceanic arc during dextral transpression, Southern Volcanic Zone, Abitibi Subprovince Canada

The Archean Abitibi Subprovince. divided into Northern (NVZ) and Southern (SVZ) Volcanic Zones, is characterized by the crustal-scale Destor-Porcupine-Manneville Fault Zone (DPMFZ), which links the SVZ and NVZ, and the Cadillac-Larder-Lake Fault Zone (CLLFZ), which separates the Abitibi and Pontiac Subprovinces. The DPMFZ and CLLFZ represent major deformation zones that record over 60 million years of Archean deformation. The dextral transpressional phase in the NVZ, which represents incipient SVZ deformation. occurred between 2700 and 2692 Ma and is characterized by Southeast (SE)-trending dextral faults (e.g. Macamic Fault), Synorogenic flysch sedimentation is focussed at the interface between the SVZ-NVZ and Pontiac-Abitibi Subprovinces. The SE-trending Parfouru fault. linking the two major trench fault systems, is interpreted as a reactivated leaky transform fault and is associated with synorogenic flysch sedimentation. The early monzodioritic suite of the Preissac-Lacorne batholith was related to DPMFZ thrusting (ca. 2692-2690 Ma). The change from early thrusting to transcurrent motion is recorded in the Duparquet strike-slip basin, which formed between 2690 and 2680 Ma along the DPMFZ, and the Granada pull-apart basin, which evolved between 2680 and 2670 Ma along the CLLFZ. The timing of these basins indicates a diachronous evolution. Renewed thrusting affected the Granada basin but not the Northern Duparquet strike-slip basin, so that a southward migrating deformation front is inferred. Late exhumation resulted in extension along both fault zones and was responsible for the juxtaposition of medium- and low-grade metamorphic rocks. The monzogranitic suite of the Lamotte pluton, which occurred between 2660 and 2642 Ma is linked to exhumation, Final dextral transpression post-dating exhumation produced shearing and folding. The SVZ of the Abitibi Subprovince shows the salient attributes of modern oblique orogenic collisions, with alternating phases of thrusting and strike-slip movement along crustal-scale faults during dextral transpression. (C) 2002 Published by Elsevier Science B.V.