ORE MINERALOGY AND POLYMETAMORPHOSED PNATURE OF THE ARCHEAN Zn-Cu-Fe MASSIVE SULFIDE DEPOSITS AT THE GARON LAKE MINE, MATAGAMI, QUEBEC, CANADA

Abstract

Massive Zn-Cu-Fe sulfide deposits at the Garon Lake Mine occur in three sulfide lenses in a group of metamorphosed rhyolite crystal tuffs, metasediments and basalts. The major ore minerals are sphalerite, chalcopyrite, pyrrhotite and pyrite. Minor associated silicates are actinolite, tremolite, chlorite, albite and quartz. Rounded detrital pyrite, magnetite and chert grains and diagenetic pyrite are the only preseved premetamorphic features. Middle amphibolite facies regional metamorphism is marked by sulfide-silicate foliation, and syntectonic porphyroblasts of pyrite. After the intrusion of a granodiorite pluton, pyrite was fractured, and the other sulfides developed wedge-shaped twins. These minerals were subsequently involved in porphyroblasitic and polygonal granoblasticgrowth and annealing. Cordierite and anthophyllite developed fromchloritized wallrocks. During retrograde changes, some pyrrhotite wasconverted to pyrite, marcasite and magnetite. On the evidence of textures and mineralogy, the deposit is synsedimentary-diagenetic and of distal type