Metallogenesis and Mineralization of Intraoceanic Arcs II: The Aeolian, Izu-Bonin, Mariana, and Kermadec Arcs, and the Manus Backarc Basin--Introduction

Abstract

It is estimated that ~75% of Earth’s volcanism occurs on the seafloor, especially at divergent plate boundaries like the East Pacific Rise and the mid-Atlantic Ridge (Crisp, 1984). These features are known as mid-ocean ridges (MORs), which are large-scale lineaments marking areas of seafloor spreading where lavas are extruded onto the seafloor, and subseafloor dike emplacement is common. A metaphor commonly ascribed to this process is “conveyor belt,” where newly formed oceanic crust, invariably of basaltic composition, moves inexorably away from the axis of the MORs as the forces of plate tectonics take hold. Conversely, at the other end of this conveyor belt are convergent plate boundaries where the oceanic crust, now millions to more than a hundred million years old, is subducted beneath another plate of either oceanic or continental crust. These boundaries dominate regions of the south and western Pacific, and are typically marked by deep trenches on their seaward side, with chains of volcanoes (or volcanic arcs) on their landward side (Fig. 1). These volcanoes sit on top of the overriding plate, typically between ~70 and ~175 km (with a global average of 105 km) above where the subducted plate begins to melt and/or triggers melting of the base of the overriding plate (Syracuse and Abers, 2006). Fig. 1 Map of the central and western Pacific region is a transverse Mercator projection (CM 162° E). Inset shows a map for the Tyrrhenian Sea (part of the Mediterranean Sea), which is a normal Mercator projection. Both maps were created from ETOPO1 data (i.e., a 1 arc-minute global relief model of Earth’s surface that integrates land topography and ocean bathymetry; Amante and Eakins, 2009) downloaded from NGDC (http://www.ngdc.noaa.gov/mgg/global/global.html). 1 = Marsili, 2 = Palinuro, 3 = Bonin Islands, 4 = East Diamante, 5 = SuSu Knolls, 6 = PACMANUS, 7 …