Overview of VMS exploration in glaciated terrain using indicator minerals, till geochemistry, and boulder tracing: a Canadian perspective

Abstract

During the Quaternary, most of Canada's landmass was covered by ice sheets that eroded and dispersed metal-rich debris from volcanogenic massive sulphide (VMS) deposits across the landscape together with a blanket of unconsolidated debris. Therefore, boulder tracing, till geochemistry, and indicator minerals are important exploration methods for VMS deposits in Canada. This paper provides an overview of the development and application of these methods, including till sampling, appropriate size fractions of till to analyze, sample processing, and analytical techniques. Selected case histories from different regions across Canada are also presented. Copper, Pb, and Zn are indicator elements of VMS deposits, and pathfinder elements include As, Ag, Au, Ba, Bi, Cd, Hg, In, Sb, Se, Sn, and Tl. Abundances of these elements are most commonly determined in the <0.063 mm (silt + clay) fraction of till. Indicator minerals of VMS deposits are recovered from the >3.2 specific gravity heavy mineral concentrate of till and include the main ore minerals (galena, sphalerite, chalcopyrite, pyrite, and pyrrhotite), accessory minerals (native gold, electrum, cassiterite, cinnabar, and barite), and, in metamorphic terrain, metamorphosed minerals of mineralization, alteration, or exhalites, including sillimanite, andalusite, gahnite, staurolite, and spessartine. Magnetite and its chemical composition may also be a useful VMS exploration tool. Ongoing and future research of drift exploration methods for VMS deposits will focus on reducing sample size, lowering analytical costs, and identifying new indicator minerals and chemical discrimination criteria.