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).