Alignment of Circular Structures Mafic and Ultramafic Rocks: in A New Prospecting Guide in the Grenville

CIM Bulletin, 1971

A. L. DORR and A. F. LAURIN, Mineral Deposits Service, Quebec Department of Natural Resources, Quebec, Que

Because of its wide areal extent, its numerous lithological facies and its high degree of metamorphism, the Quebec portion of the Grenville province has only partly been explored and prospected. Rock types that are economically among the most interesting in the Grenville are those of mafic and ultramafic compositions, because of their great potential for coppernickel and chromium-platinum. The peculiar mode of occurrence and the distribution of these igneous masses in which copper-nickel mineralization is known to occur indicate' two common geological features: (1) aerial photographs and/or topographic maps strongly' suggest close spatial (and possibly temporal and genetic) association of most of these mineralized mafic and ultramafic intrusions with circular structures; (2) when plotted on a large-scale map comprising the Quebec portion of the Grenville, these circular structures fall along two lines which could correspond to major tectonic features. Even though the genetic links among the mineralized mafic-ultramafic masses, the circular structures and the linear features are not yet fully understood, their associations are believed to be empirically valid and should therefore be used as geological tools by those interested in exploring the Grenville for copper-mckel and possibly chromium-platinum deposits. It should be noted that these mafic and ultramafic bodies do not appear to be spatially related to anorthosite complexes.
Keywords: copper, nickel, Quebec City, ultramafic, Grenville, Grenville Province, Intrusions, Maps, mineralization, Quebec, Resources, Structure