Stratigraphy and structural analysis of the North Gold Zone at Montauban-les-mines, Quebec

CIM Bulletin, Vol. 80, No. 906, 1987

VINCENT JOURDAIN, DENIS W. ROY, Sciences de la Terre, University du Quebec a Chicoutimi, Chicoutimi, Quebec, and JEAN-MARC SIMARD, Muscocho Exploration, Montauban, Quebec

Seven lithologic units, informally characterized, were recognized in the vicinity of the Montauban orebody. The first five lie in stratigraphic order. From structural bottom to structural top these are: (1) grey composite gneiss; (2) dark grey quartz-biotite gneiss; (3) quartz-biotite-garnet gneiss hosting several calcareous, aluminous and magnesian members and gold mineralization; (4) light grey quartz-muscovite-(sericite)-biotite gneiss; and (5) metabasalts. The last two intrude the sequence: (6) amphibolite dykes and (7) pegmatite veins. The orebody lies on the inverted limb of an overturned synform verging to the west with the metabasalts marking the core of the fold. As the foliation is folded, this fold is attributed to deformation "D2"; deformation "Dl" being responsible for the formation of the foliation. A late brittle deformation developed shear zones with probable strike-slip motions. The refined stratigraphy and the identification of the structural position of the orebody provide new tools for regional interpretation and prospecting.
Keywords: Economic geology, Stratigraphy, Structural analysis, Montauban orebody.