The critical role of magma degassing in sulphide melt mobility and metal enrichment.

Much of the world's supply of battery metals and platinum group elements (PGE) comes from sulphide ore bodies formed in ancient sub-volcanic magma plumbing systems. Research on magmatic sulphide ore genesis mainly focuses on sulphide melt-silicate melt equilibria. However, over the past few years, increasing evidence of the role of volatiles in magmatic sulphide ore systems has come to light. High temperature-high pressure experiments presented here reveal how the association between sulphide melt and a fluid phase may facilitate the coalescence of sulphide droplets and upgrade the metal content of the sulphide melt. We propose that the occurrence of a fluid phase in the magma can favour both accumulation and metal enrichment of a sulphide melt segregated from this magma, independent of the process producing the fluid phase. Here we show how sulphide-fluid associations preserved in the world-class Noril'sk-Talnakh ore deposits, in Polar Siberia, record the processes demonstrated experimentally.