Effects of greenschist-facies metamorphism and related deformation on the Mobrun massive sulfide deposit,Québec,Canada |
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| Authors: | A C L Larocque C J Hodgson |
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| Institution: | (1) Department of Geological Sciences, Queen's University, K7L 3N6 Kingston, Ontario, Canada;(2) Present address: Department of Geological Sciences, University of Manitoba, R3T 2N2 Winnipeg, Manitoba, Canada |
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| Abstract: | The Mobrun Zn-Cu-Ag-Au deposit in the Noranda mining camp is hosted by Archean mafic and felsic submarine volcanic rocks. The deposit comprises three massive sulfide complexes: the Main and Satellite Lenses near surface, and the 1100 orebody at depth. The rocks have been subjected to lower greenschist-facies metamorphism and related deformation, which resulted in changes in ore textures, development of shear zones and veins systems, remobilization of gold, and formation of a new mineral (electrum) within the orebodies. Both mechanical and chemical processes operated to produce secondary textures and structures resulting from brittle deformation, ductile deformation, and annealing. The specific deformation mechanisms include brittle failure and cataclastic flow, dislocation glide, dislocation creep and solution-precipitation creep. The Main and Satellite Lenses are characterized by excellent preservation of primary sulfides deposited from and reworked by synvolcanic hydrothermal fluids. These orebodies were affected to a limited degree by mechanical processes of deformation. In contrast, the 1100 orebody is characterized by a higher degree of development of textures and structures related to metamorphism and deformation, especially those formed by chemical processes. The differences may be due to the greater depth of the 1100 orebody relative to the other lenses, as regional metamorphic isograds are subhorizontal, and more extensive interaction between metamorphic fluids and the 1100 Lens. |
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