| Abstract: | Mafic to felsic predominantly marine volcanic members on the west flank of the major volcanic vent of the relatively unmetamorphosed and undeformed Archean upper Blake River Group of the Noranda area were sampled at approximately 100 m centres in a 100 km2 area for whole-rock analysis as part of an integrated exploration program during 1977–1980. Automatic processing of the resulting approximately 2000 analyses yielded not only the expected improved definition of primary rock types but also synvolcanic alteration patterns of varying intensity. Essentially two-dimensional sea floor “weathering” on paleo-bedding surfaces and the more fully three-dimensional, hydrothermal, volcanogenic, footwall alteration systems were discovered. The data, when integrated with existing drill and mining information provide a unique insight into the hidden shape of the sub-sea-floor plumbing of the recently discovered active hydrothermal, biologic systems observed in two dimensions at crustal spreading centres on today's ocean floor.Polarized compositional gradients observed within the footwall alteration patterns are interpreted to be potent exploration guides to proximal, polymetallic, sulphide facies exhalite deposits and their associated “stringer” zones. |
