Part 6. Present plate boundary seismic, volcanic and kinematic processes: Geochemistry of the volcanic rocks of the Sunda Island arc of Indonesia

Abstract

The Sunda arc represents the collision zone between the India and Asia (or China) plates. The Sunda volcanic arc extends from north of Sumatra, along the southwestern coast of Sumatra, through Java, Bali, Lombok, Sumbawa, Flores and the Lesser Sunda Islands, after which it becomes known as the Banda arc. There are a variety of tectonic environments represented along the arc. In Sumatra the crust is ~40 km thick and Palaeozoic granites show it to be relatively old. The Benioff zone as defined by the location of earthquake foci extends only to relatively shallow depths of ~200 km. Beneath Java the crust is somewhat thinner, younger; the oldest exposed rocks being? Mesozoic, and the Benioff zone extends to ~600 km beneath the Java Sea to the north. Further east, the crust is thinner (~15 km), oceanic in velocity structure and again the Benioff zone extends to great depths.