Geochemical and Isotopie Studies, Noranda & Matagami Areas

Relationships of Noranda sulphide deposits to volcanic rocks are reviewed and chemical variations within the volcanic sequence are described. The assemblages of minor elements in the pyrites and pyrrhotites of the Noranda and Matagami deposits are similar and are characterized by a high content of cobalt, tin and other elements. Isotopic compositions of lead, other geochronological data and stratigraphically disposed zonal distributions of sulphides and minor elements indicate that the deposits were formed prior to folding and metamorphism. Lead isotope data indicate that the Matagami deposits, and severa! others, were probably formed about 2.95 x 109 years ago and that the Noranda deposits may be about 50 million years younger. The volcanic sequence at Noranda is younger than the thick sequences bordering it on the east and on the west. The relationships are consistent with the hypothesis that these strata-bound sulphide deposits are coeval with their associated volcanic rocks.
Keywords: Deposits, Lead, Matagami, pyrite, pyrrhotite, Waite andesite, Waite rhyolite, Noranda, pyrite, Rock, Rocks, Volcanic rocks
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