Secondary geochemical dispersion patterns associated with the nickel sulphide deposits at Kambalda, Western Australia

Abstract

Geochemical investigations have shown that the nickel sulphide mineralisation at Kambalda is detectable by sampling and analysing the minus 80-mesh fraction of near-surface soils. Over unmineralised mafic and ultramafic rocks the distribution of Ni in soils accurately reflects bedrock Ni distribution. In the environment of sulphide mineralisation Ni is preferentially concentrated in the coarse fractions of the soils, with a corresponding depletion in the minus 80-mesh fraction. Both Ni and Cu nevertheless display strong anomalies in minus 80-mesh fraction soils in the immediate vicinity of sub-outcropping mineralisation. The distribution of Ni, and to a lesser extent Cu, in the minus 80-mesh soil fractions appears to be controlled by a strong association with secondary iron oxides which is most marked in the silt fraction. Clay mineral abundance and type appears to have little influence on the secondary dispersion of Ni in the Kambalda environment.