Abstract

The Vauze massive sulfide lenses and underlying zones of disseminated sulfides lie at the same andesite/rhyolite contact as neighboring deposits, and have long been interpreted as volcanogenic. The andesites and rhyolites are submarine flows that have undergone only weak metamorphism and maintain shallow dips. They form part of a thick sequence of alternating andesitic and rhyolitic formations, which are the upper parts of the Blake River Group, within the Archean volcanic and sedimentary assemblage of the Abitibi belt.Stratiform sulfide lenses, in one case overlying explosive rhyolite breccia, lie on the two remaining flanks of a domelike feature on the top of the rhyolite. Massive copper-rich and pyrrhotite-bearing sulfides in the lenses and a fragmental form of these massive ores are overlain by layered pyritic-zinc sulfides and chert. Postore diorites separate these lenses from alteration in a pipelike fracture zone plunging steeply through the dome and several underlying formations. Stringers and disseminations of chalcopyrite occur with strong chloritization and sericitization in this zone.In a reconstructed model of the deposit, the features of the breccias of both rhyolite and massive sulfide point to their being the products of explosion from the pipe area, which was a conduit for solutions emerging as hot springs, and from sulfides deposited over the pipe and on the flanks of the dome. The sulfides must have formed as hard sulfide sinters in restricted lenses on the steep sides of the dome, from solutions flowing over them and without the metals having passed thraugh the medium of sea water. Later andesites covered the deposits.

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