Magma genesis in the New Britain island arc: further insights into melting and mass transfer processes

Abstract

Quaternary volcanic rocks from the New Britain island arc display a wide range in chemical compositions. The source of the lavas shares isotpic characteristics with Indian Ocean type mid-ocean ridge basalt (MORB). In contrast, the high field strength elements (HFSE) are extremely depleted in the volcanic front rocks compared with MORB. We propose that this results from a previous melt-extraction event - hypotheses invoking residual phases in either the mantle wedge or subducting slab cannot account for the depletion relative to MORB. In addition, elements other thanthe HFSE are also affected. Chemical signatures in parts of the New Britain arc and Manus Basin may relate to a previous subduct..