New insights into the source of gold in the Youjiang basin, SW China

Abstract

Mantle plume rich in gold is considered to be important for the formation of giant epigenetic gold deposits. The Youjiang basin, SW China, is the world’s second largest Carlin-type gold province, but the ultimate source of its gold remains enigmatic. In this study, we report that the Middle−Late Permian basaltic rocks in the basin are rich in native gold grains. These gold grains are scattered in the interstices of pyrite and marcasite and in the amorphous silica cavities. Mineralogy and S-Pb isotope geochemistry of the auriferous sulfides suggest that the gold was largely derived from the gold-rich Late Permian (ca. 260 Ma) Emeishan plume and was released to a near-surface volcanogenic massive sulfide (VMS) metallogenic system, where it accumulated. The native gold grains from the basalts may have been inherited by the younger (ca. 140 Ma) Carlin-type ores in the Youjiang basin, which are indicative of gold pre-enrichment in the basin. Our study highlights that golden plume upwelling could carry abundant gold into the upper crust, even into shallow-level metallogenic systems, and thus provides an alternative view on the source of gold in the Youjiang basin.