Abstract

The Sunda arc is a simple-looking island arc at the western tip of Pacific Ring of Fire, extending from the Andaman islands in the North and Sumatra in the West to the small volcanic islands in the north of Savu Sea in the East. The current active arc is built on top of composite crustal blocks, and has been active since Miocene. This more recent style of activity occurred after the Cretaceous subduction period ceased, and arc activity shifted towards the north. Today, the Sunda Arc is one of the most active volcanic arcs in the world, with 95 Quaternary volcanic centers. The groundwork on Sunda arc magma geochemistry was laid in the 1970s (as early as 1973), and has now reached a new peak of data accumulation and complexity. This allows us to look through a large-scale systematics of arc geochemistry. Understanding this geochemical framework should provide an opportunity to understand the interplay between the three main subduction zone components (i.e., mantle source, subducting slab, and the overriding crust) and their role in the generation of magmas along Sunda arc. This talk will provide (1) an introduction to the general geochemical systematics along Sunda arc, followed by (2) a closer look into the across-arc chemical systematics in Central Java. In the first part I will briefly show you the geochemical variation of volcanics from along the arc to show the variable association with the underlying crustal blocks. In the second part I will highlight my recent work, which seeks to untangle the subduction contribution across Merapi-Muria volcanic line in Central Java, where the slab-mantle wedge interface goes deeper than the rest of the arc segments, using trace elements and radiogenic isotopes