The Big Lake volcanogenic massive sulphide (VMS) occurrence, located in the Schreiber-Hemlo belt of the Superior Province, was discovered in March 2006 near Marathon, Ontario. It is hosted in a mafic-ultramafic metavolcanic sequence lacking felsic volcanic or volcaniclastic rock, and consists of a thin, locally anastomosing sheet of veined pyrrhotite, chalcopyrite, and sphalerite currently defined over a plan area of approximately 0.5x0.5 km, along the base of a series of peridotite and pyroxenite cumulates termed the Big Lake Ultramafic Complex (BLUC)
