Indium and gallium enrichments in zinc orebodies in the Taebaeksan region, Korea

Abstract

Indium (In) and gallium (Ga) have been regarded as the critical elements due to a large recent demand on high-tech applications but their relatively low crustal abundance. The presence of variable In and Ga contained in sphalerite has recently been reported from numerous magmatichydrothermal zinc orebodies in the Taebaeksan metallogenic region in Korea. Here we report chemical compositions of lithologies including granitoid intrusions and sedimentary sequences in the region and compare with associated sphalerites to investigate geological distributions and enrichment processes of In and Ga. While In in the lithologies are not generally detected by LA-ICP-MS, high concentrations up to 630 ppm in sphalerite suggest a significant In enrichment by magmatic-hydrothermal fluids. Major zinc mines show high In concentrations of an average 100 ppm suggesting a potential of economic In orebodies in the region. Despite relatively moderate Ga contents up to 24 ppm in the hosting lithologies, Ga enrichment in sphalerite up to 66 ppm is rather limited compared to the In enrichment. The types and mineral assemblages of magmatichydrothermal sphalerite-bearing ores indicate that In is concentrated in relatively higher temperature, whereas Ga tends to be enriched in lower temperature. The enrichment processes of In and Ga in sphalerite might be strongly related to their complexations in the magmatic-hydrothermal fluids. High salinity in the fluid is favorable to form an In-chloride complex for mobilization and enrichment of In into sphalerite. Conversely, Ga-hydroxide complex might not be stable at relatively high temperature which could limit an economic enrichment of Ga in sphalerite in the region.