Khalid Yahia HBSc thesis abstract

Mackenzie River granites (MRG), are Archean deformed granites exposed in many locations alongside Highway 11/17 east of Thunder Bay. Microcline and plagioclase are the dominant minerals with quartz that slightly varies in proportion from one location to another. The samples that were examined petrographically are classified as ten granite samples, two granodiorite, one tonalite, and one quartz monzonite. Greenish chlorite was observed in most of the fractures in the study area. Two main populations of fracture strike were recorded in the study area. A NE-SW strike of fractures and faults was the major and dominant strike direction. This direction of strike agrees perfectly with one arm of the Midcontinent Rift (MCR). The second major population of structures strikes NW-SE with fewer fractures compared to the NE-SW strike of structures. The deformation history of MRG is documented by four main deformational features: penetrative brittle-ductile deformation, brittle deformation including a cataclasite-filled fault, chlorite-filled fractures, and quartz-filled fractures. Subgrains, serrated grain-boundaries, and undulose extinction are the main dislocation-creep features in quartz besides the bent and deformed twins of plagioclase and microcline. These dislocation-creep features were observed as evidence of penetrative brittle-ductile deformation at a depth of more than 15km for MRG at the time of deformation. Brittle deformation is indicted by the fractures in MRG and cataclasite-filled fault. Cataclasite-filled fault is identified by its 0.2-0.5mm crushed angular mineral pieces that have the same mineralogy as MRG. Chlorite-filled fractures are Archean, supported by the cross-cutting relations in the field. Quartz-filled fractures are younger than Gunflint Formation (GF) as they are present in (GF).