AbstractsEarth & Environmental Science

Carbonate-hosted Zn-Pb deposits of the Kootenay Arc in southeastern British Columbia and northeastern Washington typically have narrow and poorly developed alteration footprints, and so generate significantly smaller visible and geochemical haloes when compared to many other mineral deposit systems. However, these carbonate-hosted deposits can have invisible alteration footprints that are much broader when detected with analyses of light stable isotopes. The intensity of this isotopic alteration increases from peripheral regions into the centre of mineralization with greater shifts towards lighter, or more depleted, isotopic values as a result of more fluid:rock interaction. These depleted stable isotope values can therefore provide information about fluid flow during mineralization and have potential value in the search for sulphide mineralization. Studies of C and O isotopes from the host rocks of four Zn-Pb mines within the Kootenay Arc (H.B., Jersey, Remac and Pend Oreille) in addition to geochemical analyses have revealed at least two separate isotopic alteration signatures. These two different isotopic alteration signatures are inferred to represent two different hydrothermal fluids; the Remac Mine exhibits a much lower temperature isotopic signature when compared to the H.B., Jersey and Pend Oreille mines. Despite the difference in isotopic signature, all four mines are thought to represent Mississippi Valley-type mineralization. The most depleted isotopic values have been interpreted to reflect the highest temperature and most permeable systems. At the mine-scale, isotopic depletion highlights permeable rock-types and proximity to fault zones rather than proximity to Zn-Pb mineralization. At this scale it is therefore necessary to utilize additional geological information, such as geochemistry, to delineate rock-types that could be potential hosts of Zn-Pb mineralization. These two distinct isotopic signatures, in addition to geochemistry and other geological information, could therefore be utilized to vector towards, or re-evaluate, similar Mississippi Valley-type Zn-Pb mineralization within this region.