Selenides and sulphides from Iron Monarch, South Australia

Abstract

The selenide assemblage at Iron Monarch, South Australia, has been characterized using electron microprobe analyses. The principal selenide minerals are: eucairite (Ag1.03Cu0.98Se0.99S0.01), naumannite (Ag2.03Cu0.02Se0.96S0.04) and bohdanowiczite (Ag0.96Cu0.04Bi1.01Se1.98S 0.02) and these occur with francisite in barite. Also present are clausthalite, bismuthinite, wittichenite and a number of copper sulfides. The occurrence is of hydrothermal origin and is thought to be associated with the intrusion of quartz diorite dykes, at temperatures between 133°C and 250°C. The compositions of coexisting sulfides and selenides show strong partitioning of Se into the Ag rich minerals and S into the Cu rich minerals.