June 2003

New gold targets in the Chibougamau area
Regional geology

Patrick Houle
Géologie Québec

The Chibougamau mining camp is characterized by the presence of a vast layered intrusion, the Lac Doré Complex (DLC), cored by the Chibougamau Pluton (PDF Format, 64 kb). The importance of these two elements can be established at many different levels, whether as the main centre of volcanism, as the driving force behind the different types of ore deposits, and as a structural feature that governed response to deformation over a period of 30 Ma during the Archean (Daigneault, 1998). The crescent-shaped Chibougamau Pluton occupies the axial part of the Chibougamau anticline. It represents a multiphase synvolcanic intrusion (2718±2 Ma; Krogh, 1982) derived from the successive emplacement of magmas differentiated at shallow depths.

Consequently, substantial evidence suggests that porphyry-type and lode-type occurrences in the Lac Doré mining camp are products of a single but extensive pre-tectonic magmatic-hydrothermal ore-generating event, coeval with the emplacement of the Chibougamau Pluton and the construction of the second volcanic cycle in the Chibougamau area. The variety of ore deposit types observed in this mining district, which are particularly well developed along the northern and southern limbs of the Chibougamau Pluton, appears to be the result of normal or reverse movement along certain major faults, and of the local erosion level (Pilote et al., 1998).

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