The stratigraphy, structural geology and geochemistry of the Fox Lake massive sulfide deposit

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Olson, Philip Eugene
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The Fox Mine was a Proterozoic copper-zinc, volanogenic massive sulfide deposit located in northwestern Manitoba. It was hosted by tholeiitic and calc-alkaline, sodic series volcanic and associated sedimentary rocks. The area has undergone middle amphibolite grade metamorphism. The deposit comprised two major massive sulfide lenses, produced by separate hydrothermal vents. Both displayed typical metal zonation with lowermost copper-rich stringer ore, central massive copper-rich ore and uppermost stratified zinc rich ore. The lenses were laterallly continuous with altered felsic metavolcanic rocks. The western extension is obscured by thick accumlations of siltstones and pyritic mudstones. A thin horizon of iron formation coincides with the eastern extension. The structural evolution of the Fox Mine area involved subvolcanic plutonism, early isoclinal folding (F1), tight E-trending shear folding (F2) followed by a period of faulting and shearing (D3) that segmented and offset the sequence of strata. The orebody occurred on the overturned limb of an early, sub-horizontally plunging, isoclinal fold. Altered felsic metavolcanic rocks 800 meters south of the mine constitute a similar geological environment. They represent a detached, folded (F2) repetition of the favorable stratigraphy.