Fractured latest Devonian granites of the West Moose River pluton along the Cobequid Shear Zone, Nova Scotia: implications for regional mineralization

Latest Devonian (~365–358 Ma) A-type granites in the Cobequid Highlands host complex sequences of rare earth element (REE) and other hydrothermal minerals. The West Moose River pluton is the only pluton truncated and brittly deformed by the mid Carboniferous (~327 Ma) strike-slip Minas Fault Zone during the Alleghanian orogeny. Fractures in the granite provide a record of several deformational and hydrothermal events with distinct mineral assemblages. Early sodic alteration produced albitisation of feldspar, and riebeckite and tourmaline veins. The δ 18 O of albite and albitised granite (5–6 ‰) is similar to other regional granites, suggesting a mantle source of albitising fluids. Nearby halite deposits are younger and thus not a source of Na. Early chlorite veins were followed by potassic alteration and hydrothermal biotite, and by diabase and lamprophyre dyke emplacement. Euhedral magnetite occupies new cross-cutting fractures and vugs, correlated with regional iron oxide- carbonate- sulphide ...