Occurrence and Enrichment Mechanism of Silver in Yushui Copper Polymetallic Deposit in East Guangdong

ABSTRACT

The Yushui copper deposit in Guangdong, China, is a medium‐sized high‐grade VMS‐type deposit consisting mainly of stratiform orebodies (308 Ma) and footwall stockwork orebodies, with minor vein‑type orebodies hosted in hanging wall dolomite along joints and faults. Three mineralisation stages are recognised: Cu‑polymetallic sulphide‑quartz (I), Cu–Ag–polymetallic sulphide‐quartz (II) and Ag–Cu–polymetallic sulphide‐quartz‐calcite (III). EPMA and TIMA analyses show that silver occurs as invisible silver (dominant) and visible silver. Invisible silver is hosted via isomorphic substitution in bornite and other copper sulphides, whereas visible silver occurs as independent minerals, dominated by stromeyerite and argentite. Silver was transported as chloride complexes at early high‑temperature conditions and incorporated into copper sulphides during cooling. With decreasing temperature and oxygen fugacity and increasing pH, silver shifted to hydrosulphide complex transport and eventually precipitated as independent silver minerals. The contrasting occurrence of invisible silver in stratiform VMS orebodies and visible silver in vein‑type orebodies provides key implications for exploration targeting, resource evaluation and mineral processing optimisation in analogous polymetallic deposits.