The distribution of trace elements in chalcopyrite

Abstract

The distribution of trace elements in common sulphides has implications for ore genesis, mineral processing, the environment, and also, potentially, for mineral exploration. Although the literature contains abundant data for pyrite, sphalerite, galena, bornite and other common sulphides, there was, until recently, a relative lack of trace element data for the most common copper ore mineral, chalcopyrite.

Our reconnaissance study of chalcopyrite chemistry in different genetic types of ore (epithermal, porphyry, skarn, massive sulphide) by in-situ laser-ablation inductively-coupled mass spectrometry has shown that chalcopyrite contains measurable concentrations of Mn, Co, Ni, Zn, Ga, Se, Ag, Cd, In, Sb, Sn, Te, Hg and Pb incorporated into the matrix and Pb, As and Bi as inclusions.

Chalcopyrite is found to be a systematic carrier of Ag and Sn (up to hundreds and thousands of ppm, respectively). It also incorporates In and Cd, albeit at concentrations of at most a few tens of ppm (lower than in coexisting sphalerite). We have also found no evidence of incorporation of Bi above concentration levels of ~ 1 ppm.

This study has completed a preliminary assessment of possible mechanisms of trace element substitution, including Ag (for Cu), Mn, Co, Ni, Zn, Ga Cd, Sn, Hg, Pb (for Fe) and Se and Te (for S). No intra-grain compositional zoning in the chalcopyrite has been detected within samples.

The chalcopyrite dataset has also shown systematic variations between element concentrations and ore type of formation with epithermal deposits containing higher concentrations of dominantly chalcophile elements and porphyry deposits containing lower concentrations of more siderophile elements. These differences in the trace element endowment of chalcopyrite offer potential for discriminating between different deposit types.