Controls on Tellurium in Base, Precious, and Telluride Minerals in the Panormos Bay Ag-Au-Te Deposits, Tinos Island, Cyclades, Greece

Abstract

Tellurium-bearing base metal assemblages dominate the eight stages of mineralization in quartz ± calcite ± adularia ± illite epithermal Au-Ag-Te veins at Panormos Bay, Tinos Island, Cyclades. Tellurium-bearing sulfides and sulfosalts both preceded and followed the main, telluride-forming event (stage V). The complex stage V telluride assemblage was characterized by a sequence of early Ag-, middle Cu-, and late Au-bearing tellurides. There is textural evidence for epitaxial growth of the tellurides. Phase separation of carbon dioxide would have caused H2Te(g) to partition into a gaseous phase and resulted in pH neutralization. Due to rapid up-vapor transport, tellurium-bearing vapors probably supersaturated, condensed as droplets, and were resorbed into the ore-forming solution. These mechanisms enhanced local Te enrichment in the mineralizing liquid, above equilibrium, of ∑Te as H2Te(g) (i.e., log f H2Te(g) values of −0.5 to −1.5), and resulted in epitaxial growth of stage V tellurides. Epitaxy in the Panormos Bay case can be simulated by the Stranski-Krastanov crystal growth model. For supersaturation ratios with S values of 1 and 4, we predict an overall increase of the nucleation rate of tellurium and subsequent telluride precipitation.