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The kuroko deposits of NE Honshu are a key type deposit for the study of volcanic massive sulfide deposits. However, these deposits have not been studied in detail since the early 1970s and knowledge of their mode of formation is now dated. In this study, we present the analysis of 12 samples of the kuroko deposits, 12 samples of submarine hydrothermal minerals from the Sunrise deposit and 6 samples from Suiyo Seamount, both of which are located on the Izu-Bonin Arc, for 60 elements. For the kuroko deposit, Sb>Cd>Pb>As>Ag>Zn are highly enriched, Au>Ba>Bi>Cu>Mo are moderately enriched, In>Tl are somewhat enriched and Fe is not significantly enriched relative to the average continental crust. Within each of these deposits, a similar pattern of element association is apparent: Zn-Pb with As, Sb, Cd, Ag, Hg, Tl and Au; Fe-Cu-Ba with As, Sb, Ag, Tl, Mo, Te and Au; Si-Ba with Ag and Au; CaSO₄ nil. The enrichment of the chalcophilic element in these deposits is consistent with hydrothermal leaching of these elements from the host rocks which are dominantly rhyolite-dacite in the case of the kuroko deposits, rhyolite in the case of the Sunrise deposit and dacite-rhyolite in the case of the Suiyo Seamount deposit. However, this pattern of element enrichment is also similar to that observed in fumarolic gas condensates from andesitic volcanoes. This suggests that there may be a significant, perhaps even dominant, magmatic contribution to the composition of the hydrothermal fluids responsible for the formation of the kuroko deposits, although it is not yet possible to quantify the relative contributions of these two sources of elements.

The compositional data show that Sunrise and Suiyo Seamount deposits are much closer compositionally to the kuroko deposits from NE Honshu than are the submarine hydrothermal deposits from the JADE site in the Okinawa Trough which contain, on average, significantly higher concentrations of Pb, Zn, Sb, As and Ag than each of these deposits. In spite of the greater similarity in tectonic setting of the Hokuroku Basin in which the kuroko deposits formed to the Okinawa Trough (intracontinental rifted back-arc basin) compared to Myojin Knoll and Suiyo Seamount (active arc volcanoes), it appears that submarine hydrothermal deposits from Myojin Knoll and Suiyo Seamount are closer analogues of the kuroko deposit than are those from the Okinawa Trough.