Part 6. Present plate boundary seismic, volcanic and kinematic processes: The origin of magmas at convergent plate boundaries

Abstract

The dominant lava types produced by volcanism in young island arcs are basalts close to silica-saturation, basaltic andesites and andesites. These lavas are often referred to two associations ? the island arc tholeiitic association, found in volcanoes ~80?150 km above the Benioff Zone, and the calc-alkaline association, in volcanoes ~100?250 km above the Benioff Zone. The major possible source materials for primary magmas of the two associations are former oceanic crust (in the form of eclogite) in the subducted lithosphere slab, and the overlying wedge of peridotitic mantle (Figs. 1 and 2).