Abstract

Structural analysis of the Blake River Group volcanic rocks in the Rouyn–Noranda region shows the formations to be distributed largely in Z shapes, resulting from the interference of two early fold systems oriented west-northwest–east-southeast and east–west, respectively. The first of these two fold systems is probably related to the shortening associated with left-lateral movement along the two major fractures in the region, namely the Porcupine–Destor and Larder Lake – Cadillac faults. The second system appears to be the result of north–south compression perpendicular to the two major fractures.The two major faults, the first system of early folding, the normal and reverse faults, and the minor dextral and sinistral strike-slip faults that have been observed in the Blake River Group rocks can all be integrated into one tectonic system, that of wrench fault tectonics. The orientations of the principal structures recognized in the Abitibi Belt (major shear zones, folding, and faulting) suggest that the deformation mechanism for the rocks in the belt could be a large lateral movement controlled by megashears similar to those observed at present on the California coast (San Andreas Fault), in New Zealand (Alpine Fault), and in Sumatra (Semangko Fault).

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