Hydrothermal Alteration Study of the VMS-hosting Paleoproterozoic Bear Lake volcanic suite, Flin Flon Belt, Northern Manitoba

Abstract

The Bear Lake suite of the Paleoproterozoic Flin Flon Arc Assemblage consists of a large basaltic andesite shield volcano crowned by a caldera containing effusive to volcaniclastic rhyolite to andesite flows and a thick pelitic unit, the latter which hosts the White Lake and Cuprus volcanogenic massive sulphide deposits (VMS). The Bear Lake suite is also host to an extensive zone of epidote-enriched synvolcanic hydrothermal alteration over 11 km by 3 km in dimension. This alteration zone is similar in size to that of the VMS-rich Archean Noranda cauldron succession and yet contains an exponentially smaller VMS tonnage. Detailed mapping and geochemical analysis of the alteration zone indicates redistribution of large amounts of base metals unaccounted for in the presently known VMS deposits, suggesting good base metal exploration potential still exists within this oceanic arc succession.

The Geology and Metallogeny of Volcanic-Hosted Massive Sulfide Deposits: Variations through Geologic Time and with Tectonic Setting

“…This flow involved the drawdown of cold seawater and convection and heating of this seawater in the volcanic rock pile to produce hydrothermal fluid that vented at the sea floor. Several studies have demonstrated that the deeper parts of these regional alteration zones have been leached of metal and, in some cases, sulfur, with mass-balance calculations indicating that the amount of metals leached exceeds the metal present in known deposits (Gibson et al, 1983;Brauhart et al, 2001;Huston et al, 2001;Galley et al, 2009;Jowitt et al, 2009).…”