Metallic mineral deposits of the Grenville Province, southeastern Ontario

CIM Bulletin, Vol. 78, No. 875, 1985

T.R. CARTER and A.C. COLVINE, Ontario Geological Survey, Toronto, Ontario

Rocks of the Grenville Province in southeastern Ontario are currently largely dismissed by many geologists as having little or no potential for discovery of significant deposits of metallic minerals. The present study demonstrates that the area contains numerous deposit types which elsewhere are major metal producers. Therefore, there is significant unrealized potential, especially for gold, zinc, uranium, and possibly copper. The variety of deposits of metallic mineralization include stratiform zinc in marbles; stratabound base metal sulphides in volcanic and sedimentary hosts; gold-quartz veins; quartz-magnetite iron formation; copper-nickel and iron-titanium in intrusive rocks; magnetite skarns; molybdenum in skarns and pegmatites; uranium and thorium in pegmatites, veins, and calc-silicate gneisses; hematite veins; dolomite marbles (magnesium); and barite-fluorite-celestite-galena-calcite veins. There has been significant production of iron, lead, zinc, magnesium, gold, silver, and uranium. The vast majority of the metallic mineral deposits are confined to late Precambrian supracrustal and related intrusive rocks of the Grenville Supergroup. Many of the deposits are stratiform and/or stratabound and occur within units toward the top of major volcanic successions and in the lower portions of younger carbonate-clastic sedimentary successions. Processes responsible for mineral concentration in the area include: (I) syngenetic hydrothermal activity related to both volcanism and sedimentation; (2) epigenetic processes related to diagenesis, regional metamorphism, and igneous intrusive activity; (3) magmatic processes related to igneous intrusions; and (4) supergene concentration and enrichment. The genetic classification of the mineral deposits presented is based on observed geological relationships and these interpreted geneses. The deposit types have counterparts in volcanogenic and sedimentary exhalative, Mississippi Valley type, magmatic, contact metasomatic, and lode gold deposits. Many of the exploration criteria for deposits of these types may be applicable in the Grenville Province, despite the generally high metamorphic grades and complex deformation.
Keywords: Economic geology, Metallic minerals, Grenville Province, Mineralization, Syngenetic processes, Epigenetic processes, Magmatic processes, Supergene processes.