Sebastian Cuervo, MSc
S. Cuervo1, G. Olivo1
1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario, Canada
The marble-hosted Long Lake zinc deposit occurs along the contact zone of the marble rocks of the Proterozoic Greenville supergroup with intrusive rocks within the Greenville Central Metasedimentary Belt. Controversial genetic models have been proposed for similar marble-hosted deposits in the Grenville Province; therefore, understanding the processes that controlled the formation and transformation of zinc mineralization is essential for developing exploration strategies for zinc in the Grenville Province and similar terranes. In this study, historical data have been integrated with new field and drill core logging observations, lithogeochemical and petrological data into a 3D geological model to better constrain the geometry of the ore zones and delineate their spatial relationship with various magmatic events and igneous and marble host rocks. Zinc mineralization occurs as lenses up to 5 m thick in two main ore zones with distinct mineralogy and geochemical signatures. Sphalerite is associated with pyrite, subordinate pyrrhotite, chalcopyrite, galena, and molybdenite, calcite, phlogopite, talc, and chlorite, with the abundance of these minerals distinct in the two ore zones. These minerals filled embayments and fractures within calc-silicate minerals such as garnet, pyroxene, and amphibole, indicating that the zinc mineralization formed after peak-metamorphic conditions. Pyrite-bearing zones also occur in halos (up to 3 m) surrounding some of the zinc-rich lenses. Outside the mineralized zones, garnet and pyroxenes are well preserved. Zinc mineralized zones are consistently enriched in Cd, Hg, In, Mn, Se and S, which show high correlation with Zn. Bismuth, Pb, Sb, and Sn have also yielded high values within the zinc mineralized zones, but their enrichment extends to halos (0.1-2 m thick) surrounding these zones. These findings are not consistent with historical interpretations that the Long Lake zinc deposit is a metamorphosed sediment-exhalative deposit and indicate that other processes were involved in its formation after peak metamorphism in the Grenville Province, which may have involved contribution from magmatic sources.