STRUCTURAL LAYERING AT THE JUNCTION OF ARCHEAN QUETICO AND WAWA SUBPROVINCES, QUETICO PROVINCIAL PARK, ONTARIO

The junction between the Archean Quetico and Wawa subprovinces in the vicinity of Kawnipi and McKenzie Lakes, Quetico Provincial Park, Ontario is intensely deformed into a major recumbent synform and an adjacent recumbent antiform. These two folded structures are underlain by a major structural discontinuity that resembles the lower surface of a recumbent nappe or a thrust surface. The "outcrop" trace of this structural discontinuity follows, over a distance of 20 km, an "S-shaped" erosional depression now filled by Kawnipi Lake. A sequence of Wawa subprovince amphibolites overlain by tonalite-granodiorite occupies the core of the recumbent McKenzie Lake synform. The contact between the amphibolites and tonalite is a major zone, at least tens of meters thick, of plastic intermixing and ductile shearing. This highly sheared lithic contact can be traced through a distance of approximately 60 km, along the limbs and around the noses of the recumbent folds. This distribution, along with detailed mapping of faults and folds within the core rocks, demonstrates that the tonalite-granodiorite within the cores of the recumbent folds forms a structurally detached unit which is internally folded and faulted. This complexly deformed structural package moved into its current position at some intermediate stage of compressional deformation across the Quetico-Wawa subprovince junction, possibly using an earlier segment of the Quetico-Wawa junction as a zone of near-horizontal slippage. Although multiple shear layering is present on a variety of scales, kinematic indicators are rare. Even where lineations can be measured in the field, they invariably relate to late shear transport with nearly strike-slip orientation. Current field work attempts to delineate the possibility that these near-horizontal, structurally detached, complexly deformed, lithic sheets may rest on structurally lower, but similar, detached sheets of deformed rock. .