Tracing the Missing Argoland Beneath Java: Evidence from Geochemical Signature and Seismic Tomogram

Abstract

Argoland is a piece of Gondwana that collided to the southeastern margin of Sundaland during Late Cretaceous to Early Tertiary. Recently, the existence and continuation of the missing Argoland beneath southern Java have become a hot topic related to geological exploration. The involvement of crustal assimilation of Argoland plays an important role in magma genesis. It controls eruption style, magma composition and also mineral deposit type. Although some studies have indicated the presence of micro continent beneath the southern part of West and East Java, they still could not explain its existence precisely and there are some difficulties to connect one to another. Petrological and geochemical studies of twenty active volcanoes from west to east were combined with tomographic study result to elucidate the problem and give better understanding of crust architecture and interior in Java. Our study shows that some of these magmas derived from Active Continental Margin represent those produced by partial melting of mantle wedge induced by natural fluid in subduction system due to interaction of continental and oceanic crusts. In agreement with geochemical data, high velocity zone from tomographic data are clearly shown in the southern part of Late Cretaceous to Early Tertiary Melange. If that is so, the extension of Argoland in East Java seems to continue to the Central and West Java. A new map of Argoland distribution, crust architecture and interior of Java is proposed.