PROPENSITY FOR MINERALIZATION IN VOLCANOES — EVIDENCE FROM MELT INCLUSIONS
Rocks and melt inclusions (MI) from 11 volcanic centers of the Kermadec-Tofua arc, in the South West Pacific, were petrographically studied prior to chemical analysis under the ion beam. The abundance of MI with daughter minerals are volcano-specific with the most abundant found in "U", Putoto, and Hinepuia volcanoes where >50% of MI contain daughter minerals. The B , Li , Cl and S contents in MI generally increase with the silica content of the rock. Fe , Ni , Mn , Cu and Zn are common in MI of all rock types but Mo , Hg and Cu have the highest concentrations in dacite-rhyodacites. The highest concentrations of B , Ti , V , Fe , Co and Mo occur in plagioclase MI; S , Ni , Ge and Hg in pyroxene MI; Cl and Li in quartz MI; and Cu , Zn and M in hornblende MI. Different ore-forming components in volcanic rocks can be correlated with rock composition, Cl/S and B/S of the melts, the presence and abundance of mineral sinks for various elements and the occurrence of hydrothermally altered rock at depth and on the seafloor.