ARCHEAN TERRANE DOCKING - UPPER CRUST COLLISION TECTONICS, ABITIBI GREENSTONE-BELT, QUEBEC, CANADA

The northern (NVZ) and southern volcanic zones (SVZ) of the Abitibi gr eenstone belt are separated by the major E-trending Destor-Porcupine-M anneville fault zone (DPMFZ). The DPMFZ is interpreted to be the locus of Archean terrane docking between the older diffuse volcanic are of the NVZ (2730-2710 Ma) and the younger are segments of the SVZ (2705-2 698 Ma). Two distinct evolutionary; phases can be documented along the DPMFZ of the Abitibi greenstone belt and include (1) are-are collisio n occurring between 2697 and 2690 Ma, and (2) are fragmentation betwee n 2689 and 2680 Ma, Identification of these two events along the DPMFZ is based on detailed structural studies, sedimentary basin analysis, and precise U-Pb age determinations. The thrusting event, representati ve of the are-are collision phase, is characterized by shallow north-d ipping foliations (20-40 degrees) and dip-parallel stretching lineatio ns in the eastern Manneville segment of the DPMFZ. Local overturned ma fic pillowed units suggest recumbent folding. Late strike-slip or tran scurrent movement displayed in the late-orogenic sedimentary Duparquet Basin records the are fragmentation phase. Basin geometry, E-trending en-echelon folds, shallow E-plunging stretching lineations and a late NE-striking cleavage cross-cutting the folds support a dextral shear sense along the western Destor-Porcupine segment of the DPMFZ. The sed imentary facies observed in the basin are consistent with those of mod ern strike-slip basins located along the East Anatolian fault, Turkey (Hazar Lake) and the Hope fault, New Zealand (Hanmer Basin). Precise U -Pb zircon age determinations from porphyry stocks located at the nort hern and southern limits of the Duparquet Basin, yielded 2681 +/- 1 Ma and 2689(-2.9)(+3.2) Ma, respectively. These ages constrain the rapid change from thrusting to transcurrent movement. It is apparent that o nce thrusting ceased the response to oblique subduction continued in t he form of strike-slip displacement. Modern fold and thrust belts comm only show this evolution, The deformation pattern is the result of obl ique convergence. The Abitibi greenstone belt is considered to be an A rchean analogue of modern subducting oceanic plates such as those foun d in the western Pacific.