Diverse occurrences of galena-cemented sandstones in the Paleozoic, northern Appalachians, Quebec

CIM Bulletin, Vol. 80, No. 908, 1987

K. SCHRIJVER and G. BEAUDOIN INRS-Georessources Sainte-Foy, Quebec

Four occurrences of galena-cemented sandstones, exposed in the Lower St. Lawrence - Gasp&sie area, are described. They constitute a new, insufficiently explored type of deposit in Quebec. One mineralized body, a minor occurrence, is hosted in Lower Devonian rocks deposited in an estuarine, intertidal river channel during a marine regression; major cements are dolomite and sulphides. Another occurrence, a drilled prospect, is hosted in Upper Silurian rocks deposited unconformably on Cambro-Ordovician basement during a marine transgression. With galena and quartz as main cementing minerals, it is similar to some wellknown, economic sandstone-lead deposits. A third and fourth, a drilled prospect and a minor occurrence, are hosted in Upper Cambrian rocks deposited on continental slopes. In both, sulphides mainly occupy a secondary porosity. The differences between the third and fourth occurrences are: (1) cementing translucent minerals (carbonates and barite in one; chlorite in the other); (2) chronology of final subsurface dissolution (prior and subsequent to sulphide precipitation, respectively); and (3) important fracture porosity only in the barite-bearing deposit. The diversity of the four occurrences, and the unequal geological knowledge of their respective features, prohibit the formulation of uniform guidelines for further exploration.
Keywords: Exploration, Geology, Sandstone, Mineral exploration, Mineral deposits, Galena, Barite, Sphalerite.