Mineralogical and chemical characteristics of hydrothermal alteration associated with the Proterozoic Vamp Lake Cu-Zn sulfide deposit, Flin Flon area
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The Vamp Lake deposit is a stratiform, metamorphosed Cu-Zn massive sulfide deposit in the Proterozoic Flin Flon-Snow Lake greenstone belt of northern Manitoba. The deposit occurs at the contact between underlying mafic flows and overlying intermediate to felsic volcaniclastic rocks and flows in a 500 m thick and overturned supracrustal sequence. The host rocks and the deposit have been metamorphosed to middle amphibolite grade... The deposit, consists of two separate ore zones that occur at the same stratigraphic level but are about 400 m apart and in different fault blocks. The sulfide assemblages in each zone are mineralogically simple, consisting of pyrite, pYrrhotite, sphalerite and chalcopyrite... Each ore zone is associated with alteration that is both in direct contact with the mineralization (proximal), and underlies, but is separated from, the ore by relatively unaltered rocks (distal). Proximal alteration is well developed in a thin zone below one ore zone, and poorly developed above it; the other zone has a well developed proximal alteration envelope... Chemical changes associated with the development of both distal and proximal alteration zones are gains in K, and for those assemblages where trace element data are available, Ni, Cr, Ba and Au. Athough somewhat variable in behavior, Rb, Mg, Mu, P, Fe, and Si are gained in most assemblages. Ca is consistently depleted in the distal alteration zones, but is gained in the tremolitic proximal alteration assemblage which is characterized by anomalously high Mg, Cr, and Ni relative to all other rocks in the Vamp Lake area. Na, Sr, and Nb are depleted in most assemblages.