Evolution of the Hydrothermal System Associated with the ABM Replacement-Style Volcanogenic Massive Sulfide Deposit, Finlayson Lake District, Yukon, Canada

Abstract The ABM deposit, Finlayson Lake district, Yukon, Canada, is a bimodal-felsic, replacement-style volcanogenic massive sulfide (VMS) deposit (19.1 Mt @ 6.6 wt % Zn, 0.9 Cu, 2.0 Pb, 1.4 g/t Au, and 148 Ag) hosted by Late Devonian continental back-arc–related volcanosedimentary rocks of the Kudz Ze Kayah formation. VMS-related hydrothermal alteration associated with extends >1 km beyond mineralization. Zones pervasive sericite chlorite occur proximal to lenses (<50 m) both in hanging wall footwall, zones moderate ± extend laterally from mineralization into footwall for hundreds thousands meters. Geochemical data petrographic observations indicate that feldspar destruction formation white mica were main processes. In mineralization, base (e.g., Pb) trace metals Sb, Tl, Mo) form halos elevated values up 100 200 m, respectively. paragenesis conditions determined through petrography assemblages their crosscutting relationships, electron microprobe analyses compositions mica, chlorite, carbonate, illite-chlorite geothermometry. These suggest assemblage was earliest most extensive phase formed at temperatures around 215° 30°C. Overprinting sericite-chlorite 250° 15°C. 320° 10°C overprints preceding sericite-rich assemblages. Microprobe generally show Mg-rich varieties are more common earlier than Fe-rich varieties. Mineralogy derived short-wave infrared however, shows no clear spatial trends across due complex overprinting relationships between minerals.