A study of the copper-nickel-zinc deposit of Bird River Mines Co. Ltd., Southeastern Manitoba

Abstract

The "Ore Fault" copper-nickel deposit of Bird River Mines Ltd. contains an anomalous high amount of zinc mineralization. The small area containing the "Ore Fault" deposit is a faulted block containing metasedimentary and metavolcanic rocks of the Bird River Greenstone Belt and a sill-like body of ultramafic rock. The eastern part of the fault block is in sheared contact with a granite intrusion. The western part of the fault block is bounded by the 'ore fault' which also displaces the Bird River sill. Copper-nickel ratios and copper-nickel-zinc values suggest a copper-zinc mineralization overlapped by a separate copper-nickel mineralization. The host rocks appear to be ultramafic rocks which occur as small bodies in the deposit area. The copper-zinc plot does not correspond to a typical copper-zinc deposit which may be partly the result of mixing of the two proposed mineralization periods. Sulphur isotope techniques were helpful in ascertaining a possible origin for the nickel and zinc mineralization. The sulphur isotope rations obtained suggest that the nickel has a magmatic origin and the sphalerite does not have a sedimentary origin. The zinc mineralization could have originated from the mafic volcanic rock or the granite. It is suggested that the products of two different mineralization periods were mixed by a later deformational or intrusive event.