Structurally controlled Ag-Zn-Pb deposits are a distinct deposit class that has been suggested as a sub-class of orogenic gold deposits. The Sail Pond occurrence, Newfoundland, represents the first documented occurrence of this type in the Canadian Appalachians. We present the results of detailed geological, mineralogical and geochemical studies from Sail Pond, including mineral chemistry, fluid inclusion and sulphur, lead, carbon and oxygen isotope studies. Mineralization is in structurally controlled quartz- sphalerite-galena-tetrahedrite-tennantite veins in metamorphosed carbonate rocks, with up to 2% Ag in tetrahedrite and tennantite. Geological, isotopic and fluid inclusion studies show that mineralization occurred at high temperatures (> 300 °C) and at mesozonal crustal depths (> 6 km). Moderate salinity, aqueous-carbonic hydrothermal fluids were generated during the devolatilization of crustal sequences during prograde metamorphism, which leached metals from the nearby crustal rocks. Mineralization precipitated in open space fractures in brittle carbonate host rocks, where metalliferous fluids encountered a suitable sulfate source. Important similarities between typical orogenic gold deposit models and the mineralization at Sail Pond (and other structurally controlled Ag-Zn-Pb deposits in western North America) include the structural control on mineralization, association with regional scale greenschist facies metamorphism in accretionary orogenies and CO2-rich mineralizing fluids of probable metamorphic origin. This supports the classification of these deposits as Coeur d’Alene-type deposits, a subset of orogenic gold mineral deposits and highlights the exploration potential for this deposit type in the Appalachians and other metamorphosed sedimentary platforms globally.
Conliffe et al. (Fri,) studied this question.