Abstract

The Matagami mining camp is an important base metal producer in the Canadian Shield. The volcanic stratigraphy of the area is folded into the Galinee anticline which is an east-west-trending and west-plunging regional fold. The south flank consists of a low strain do-main characterized by a southeast-trending volcanic sequence dipping moderately at 45 degrees to the south. The stratigraphic succession is well defined with the Watson Lake Group at the base, comprising a lower dacitic unit and an upper quartz porphyritic rhyodacite unit. All but one of the deposits lie along the Key tuffite unit, located at the top of the Watson Lake Group.The north flank of the anticline is affected by a series of east-west- and northwest-trending high-angle reverse shears which defines the Lac Garon high strain zone. The volcanic sequence within this zone is displaced into four overlapping sigmoidal segments in which stratigraphic reconstruction is possible.The Norita massive sulfide deposit, located in the center of the north flank, has been deformed and faulted. Its internal metal zonation and its underlying stringer zone were flattened and rotated. Its present geometry suggests that it was deformed during north side-up high-angle reverse movement. This sense of strain is compatible with the displacement of the marker units inside the Lac Garon high strain zone, and the morphological modifications are believed to be consistent with the movement within this zone.It is suggested that the Norita massive sulfide deposit is a deformed equivalent of the less deformed south flank massive sulfide deposits, and in contrast with an earlier suggestion of a distal origin, shares the same genetic traits as the south flank deposits.

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