Silicate nickel and its application to the exploration of nickel ores

Abstract

The paper is based on the analytical data obtained from c. 10 000 Finnish mafic-ultramafic samples collected by the Exploration Department of the Outokumpu Co. in terms of an extensive exploration programme for nickel ores. The average abundances of nickel in mafic silicates of the rocks of peridotite-quartzdiorite series are given, as well as the frequency distributions of nickel abundances in these minerals for each rock type. The nickel partition coefficients of the mineral pairs: olivine-augite, olivine-orthopyroxene, olivineamphibole, amphibole-augite, amphibole-orthopyroxene and orthopyroxeneaugite are reported for various rock types with the emphasis on the model temperature estimation and its explorational application. The nickel percentage in the sulphide phase as against the rock types is examined and the partition of nickel between the mafic silicates and the coexisting sulphide phase revised. It is shown that sulphides tend to extract nickel from silicates, which fact is tentatively attributed either to autosulphurisation or sulphurisation due to external sulphur. The distribution patterns of the abundances of silicate nickel in mafic intrusives are discussed and it is concluded that the intrusives can be divided into two groups accordingly. Group I comprises the zoned complexes with high nickel values in the centre and Group II the stratiform or related bodies. The areal distribution of the locations of the samples with a high nickel percentage in the sulphide phase or of those with high suphide nickel are given and their bearing on decision-making with regard to strategic nickel prospecting discussed.