The proximal volcanic environment of the Scotia nickel deposits

Abstract

Detailed exploration of the stratigraphy associated with the Scotia nickel sulfide deposit has led to the identification of a succession of ultramafic flows displaying decreasing relative magnesium content both up the pile and along strike from the deposit. In addition, vent facies ultramafic pyroclastics and massive olivine peridotite flows dominate the locally thickened pile immediately overlying the ore. Interflow sediments are absent from this vent facies material but are present both higher in the sequence and along its flanks. The relatively undeformed and weakly recrystallized stratigraphy at Scotia affords an opportunity to reconstruct the development of an ultramafic succession proximal to a volcanic vent. The presence of ultramafic pyroclastics, amygdaloidal units, and a crosscutting ultramafic intrusive characterize the vent environment and distinguish the overlying pile at Scotia from that at other Western Australian nickel sulfide deposits.