Hydrothermal reconstruction and lithogeochemistry of the Argyle orogenic gold deposit, Baie Verte, Newfoundland

Abstract

The Argyle orogenic gold deposit (543,000 t @2.19 g/t Au indicated, and 517,000 t @1.82 g/t Au inferred resources) is located within Lower Ordovician Snooks Arm Group, Baie Verte Peninsula, Newfoundland. Gold mineralization is hosted as inclusions in secondary pyrite and at pyrite crystal boundaries in a ~50 m thick E-W striking, gently N-dipping tholeiitic gabbro sill. The short distance (200-300 m) from the Scrape thrust, rheological contrast within the heterogenous gabbro and a high content of coarse, reactive ilmenomagnetite were critical to the localization of gold mineralization. Two hydrothermal alteration events affected the gabbro: 1) early, pre-mineralization epidote-albite alteration; and 2) later, mineralization-related sericite-quartz-ankerite-(albite-chlorite-rutile-pyrite-gold) alteration. Within the mineralization-related alteration there are three assemblages: 1) distal chlorite-calcite-rutile ± epidote-albite (30-70 m); 2) intermediate chlorite-epidote-albite-calcite ± ankerite-rutile-hematite-sericite-pyrite (5-30 m); and 3) proximal sericite-quartz-ankerite ± albite-chlorite-rutile-sooty pyrite-gold (2-25 m). Lithogeochemistry, mineral chemistry and short-wave infrared (SWIR) spectroscopy were used to identify mineralogical, geochemical and spectral vectors to alteration and mineralization, which may aid in future mineral exploration.