919 / 2024-09-19 20:10:40

Pulsed injections of metal-rich magmatic fluids: Key drivers of mineralization in a back-arc basin hydrothermal system

metal-rich magmatic fluids; fluid inclusion; O isotope; LIBS; seafloor hydrothermal system

Session 40 - Geochemical characteristics of submarine hydrothermal systems and the evolution of hydrothermal plumes

Submarine magmatic-hydrothermal systems, in which magmatic volatiles and fluids are thought to be the major sources of mineralization elements, have been extensively documented in numerous felsic-hosted hydrothermal fields. Previous studies have primarily emphasized the contribution of magmatic volatiles in such hydrothermal systems. Despite evidences indicate that magmatic fluids have a greater capacity for transporting metals to the overlying hydrothermal system, their specific role in magmatic-hydrothermal systems remains poorly understood. This study presents compelling evidences for metal-rich magmatic fluid contribution to the Minami-Ensei (ME) hydrothermal system. Pulsed injections of metal-rich magmatic fluids into overlying hydrothermal system during mineralization process result in the elevated salinities (6.1 to 9.7 wt. % NaCl equiv) and δ¹⁸O values (1.1 to 8.0‰) in ME hydrothermal fluids, which are recorded by barite fluid inclusions and oxygen (O) isotope compositions. Laser-induced breakdown spectroscopy (LIBS) analysis indicate that the injected magmatic fluids in the ME may be Fe-rich type. The metal concentrations in magmatic fluids are several orders of magnitude higher than leaching-generated hydrothermal fluid, and their contribution to overlying hydrothermal system will substantially enhance the sulfide mineralization efficiency in magmatic-hydrothermal deposits. Hence, the magmatic-hydrothermal systems are promising targets for future sulfide ore exploration.