Microelectronic junctions in arsenian pyrite due to impurity and mixed sulfide heterogeneity
Laird, JS and MacRae, CM and Halfpenny, A and Large, R and Ryan, CG, Microelectronic junctions in arsenian pyrite due to impurity and mixed sulfide heterogeneity, American Mineralogist, 100, (1) pp. 26-34. ISSN 0003-004X (2015) [Refereed Article]
Impurities and crystal defects within the semiconducting bulk of a metal sulfide introduce energy levels within the forbidden
bandgap. These levels in turn control semiconducting type and local electrical properties within single and multi-phased sulfide
assemblages. Heterogeneity in sulfide semiconductivity linked to these impurities can lead to p-n micro-junction formation and potential distributions near the surface that may alter redox reactivity. Secondary gold ore
genesis via a micro-galvanic effect related to heterogeneity has in the past been hypothetically linked to such micro-junctions.
Understanding these regions and their interaction with weathering fluids in the regolith for example requires large-scale
imaging of potential distributions associated with near-surface micro-junctions and correlation with the responsible elemental
distributions. Here we investigate the existence of micro-electronic junctions in a mixed sulfide assemblage using scanning
laser beam induced current (LBIC) and correlate them with pyrite-chalcopyrite interfaces mapped using combined energy-dispersive
spectroscopy (EDS) and wavelength-dispersive spectroscopy (WDS) on an electron hyper-probe. Junctions in a natural assemblage
are positively identified for the first time.