What is the role of subducted volatiles and trace metals in ore-forming processes at convergent margins?
Hydrothermal activity and ore-formation have been observed in the Kermadec, Hellenic, Izu-Bonin, Tonga, Mariana, and Bismarck arc systems. Isotopes and trace elements indicate that a significant fraction of the ore-forming fluids and the metals they carry have been exsolved from volatile-rich arc magmas rather than leached by seawater during hydrothermal circulation through the crust, as for ocean ridge deposits. These ore deposits thus represent a little known aspect of the mass and element fluxes out of the subduction factory. They also provide a unique window into economically significant ore-forming processes. Many world class ore deposits from the Tertiary through the Archean (e.g., Kuroko, Noranda, and Sulfur Springs) are hosted by felsic volcanics that may have formed in a convergent margin setting.
