Trace elements in pyrite from five different gold ore deposit classes: a review and meta-analysis

Abstract

Abstract Scientific studies that use pyrite trace element signatures to facilitate interpretations of the geological history of hydrothermal gold deposits are becoming more common. Given this rise in popularity in pyrite trace element chemistry studies, a review of trace element incorporation in pyrite from various gold deposit classes is highly timely. We provide a global compilation of over 20 000 chemical data points resulting from over 5520 spot measurements of pyrites from five separate ore deposit classes, each of which is known to have high gold concentrations. The ore deposit classes considered here include orogenic gold deposits, Carlin-type gold deposits, high- and low-sulfidation gold deposits, and Au-bearing porphyry systems, whereas the pyrite minor- and trace elements that we consider include Au, As, Bi, Co, Cu, Ni, Pb, Sb, Se, Te, Tl and Zn. Meta-analyses of these data suggest that, on a global scale, both existing pyrite trace element chemistry discrimination tools and the newly-established principal component analysis (PCA) approach have a relatively low efficacy in correctly predicting the metallogenic setting in which the pyrite formed. At a deposit scale, however, pyrite trace element chemistry continues to be a useful tool for understanding Au mineralizing processes, especially when coupled with additional analytical techniques or lines of geological evidence. Further meta-analysis of the data tentatively suggests the solubility limits for the various trace elements in pyrite mineral structure and reveals that the correlations between temperature and trace element incorporation (i.e. pyrite geothermometry) are complex. The study highlights that pyrite, by virtue of its mineralogy and propensity for element substitutions, remains an important repository of chemical information related to the evolution of hydrothermal gold mineralizing systems. In as much as this repository is now readily accessed utilizing modern analytical techniques (e.g. routine LA-ICP-MS mapping of trace element distributions at ppb concentrations; mapping element distributions at the nanoscale using atom probe tomography), its full value will only be realized through continued study into the kinetics and mechanisms of trace element incorporation into pyrite structure at conditions relevant to ore-forming processes.