Abstract

The geology of the Canadian Malartic Gold Mine, Northern Quebec, shows the following features of especial interest:(i) An interesting combination of structural features affecting the position and shape of the ore bodies, (2) the presence within the area of the mine of two entirely different types of auriferous ore bodies, (3) the fact that the second of these, forming so far only a minor portion of the total ore, consists of material resembling pegmatite in appearance and composition.The main ore bodies, in graywacke, show a composite structural control. The application of stresses after the major folding resulted in the formation of a steep-pitching drag-fold which partially controlled the shape and position of contemporaneous porphyry intrusion. Continued application of the same stresses caused fracturing which was concentrated in an E-W and a NW-SE zone of brecciation. Silicification, other alteration and the formation of ore bodies in these zones followed.The "pegmatitic" type of ore occurs only within un-silicified porphyry and consists of quartz, feldspar, biotite and a variety of other minerals, filling several sets of fractures. These fractures appear to be associated with slip-planes along wide chloritic seams cutting through the porphyry stock. The structural and chronological relationship of this type of ore with the main gray-wacke ore is discussed.

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