Lead Content of Barite Coexisting with Galena

An Indicator of Oxygen Fugacity During Ore Formation

Abstract

On the basis of available thermochemical and crystallochemical data for the systems PbS-PbSO₄ and BaS-BaSO₄, it is shown that the lead content of barite (and possibly also the barium content of galena) in barite-galena assemblages can be used to define the oxygen fugacity during ore formation. A relation is derived linking the activity of PbSO₄ molecule in barite (or BaS molecule in galena) and the oxygen fugacity at given temperatures.
Fugacity diagrams for estimating the conditions of formation of various types of barite-galena ores are constructed using this relation together with thermodynamic data for other ore minerals.
As an application, the lead contents of barites from some Kuroko type deposits are used in an attempt to define the physico-chemical conditions of ore formation.