Abstract

Eight distinct metallogenic epochs have been identified within the southern Quebec Appalachians as follows:1. Precambrian-Early Cambrian intracontinental rifting of Laurentia is related to the formation of black sand paleoplacer, volcanic red-bed copper, and strata-bound Cu and Zn deposits in dolomite marble and metagraywacke.2. The Cambro-Ordovician opening of the Iapetus ocean (proto-Atlantic) resulted in the formation of uraniferous phosphorite, strata-bound Zn-Cu-Ba deposits, and magmatic Ni-Cu deposits on or along the margin of a carbonate platform.3. Early Ordovician immature island-arc formation is related to the initial closure of the proto-Atlantic Ocean and yielded chromitite and Cyprus-type volcanogenic massive sulfide deposits.4. The Middle Ordovician Taconian orogeny produced disseminated- and vein-type Cu-Mo-U-Au-Ag mineralization that formed within the frontal zone of the Taconian internal metamorphic domain.5. The Middle to Late Ordovician closure of a marginal basin of the proto-Atlantic Ocean yielded several deposit types. The eastward migration of a subduction zone under a small continental rift progressively generated kuroko-type massive sulfide, porphyry-type Cu-Au, and then porphyry Cu-Mo deposits in a mature arc setting, whereas auriferous black shales and shale-hosted sedimentary exhalative deposits were formed in a fore-arc basin.6. Late Ordovician and Silurian volcanogenic massive sulfide deposits and associated Fe and Mn formations were subsequently formed in transtensional rift basins.7. The Devonian Acadian orogeny yielded hypothermal W-Mo, mesothermal Ni-Cu-Co-Zn-As, and epithermal As-Sb mineralization.8. Niobium- and rare earth-rich carbonatites, granitophile Sn + or - W + or - Mo deposits, and diatreme-associated Au mineralization are related to the opening of the present Atlantic Ocean and associated Jurassic-Cretaceous alkaline magmatism.The eight metallogenic epochs define eight metallogenic provinces in the region which overlap and crosscut one another. Each province presents inhomogeneities in metal content and in the distribution of the types of contained mineral deposits. These inhomogeneities are related to differences such as the tectonic setting during mineral deposition, the provenance of the sediments, the depth of seawater during mineralization, and the relative location of the mineral deposit within hydrothermal convection cells.

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