Toward a revised stratigraphic and structural framework for the Obonga Lake greenstone belt, Ontario

Abstract

Located on-strike between the Sturgeon-Savant belt of the western Wabigoon Subprovince and Onaman-Tashota belt to the east, the Obonga greenstone belt holds keys to stratigraphic and structural correlation across the central Wabigoon Subprovince. Postulated unconformable relationships between Mesoarchean basement and Neoarchean volcanic cover sequences were found to be tectonic, although geochemistry of volcanic rocks indicates continental contamination. Volcanic and intrusive rocks of the southern assemblage (2734-2726 Ma) are bordered to the north by a south-facing northern assemblage of sedimentary, mafic and felsic volcanic rocks with younger ages, negating simple synformal geometry. Significant east-trending shear zones that bound and occur within the belt range from ductile phyllonite and mylonite zones with dip-slip and strike-slip geometry, to cataclastic dip-slip zones. The Wig Creek conglomerate, containing volcanic and granitic clasts, may be a Timiskaming-type deposit.