Hydrothermal manganese deposits in island arcs and related to subduction processes: A possible model for genesis

Abstract

Submarine hydrothermal manganese deposits have recently been recovered from a number of island arc settings such as the Tonga-Kermadec Ridge, Ogasawa arc-trench, Bonin arc, Mariana arc and Bismarck Archipelago. It has also been shown that large volumes of fluid are released during dewatering of subducting sediments. The amount of water subducted globally (1.5×10 15 g yr −1) is about two orders of magnitude less than that advected at ocean spreading centres. Hydrothermal manganese deposits may be precipitated from these waters. The distribution of terrestrial manganese deposits around the Circum-Pacific belt and elsewhere suggests that some of these deposits may be of hydrothermal origin related to subduction processes. At present, most of these terrestrial deposits are inadequately described to permit the establishment of the precise tectonic setting at the time of deposition of the manganese deposits and therefore an unambiguous assessment of this hypothesis.