Insights Into the Source of Relative Depletion and Enrichment of HFSE in Arc Lavas From High-Nb Basalts From the Sulu Arc (southern Philippines)

University Of California-San Diego Scripps Inst Of Oceanography, La Jolla CA

Investigators

Abstract

EAR-0001212 Castillo One of the hallmark geochemical features of volcanic arc lavas is the depletion of their concentrations of high field strength elements (HFSE such as Nb, Ta, and Zr) relative to those of other trace elements. The main objective of this study is to test in the Sulu Arc models that have been proposed to explain this geochemical feature such as melting or dehydration of the subducted basaltic crust plus overlying sediments and presence of ocean island basalt source component in the mantle wedge beneath the arc. The Sulu Arc system offers a unique opportunity to constrain the origin of HFSE depletion in arc lavas because it contains basalts with variable Nb and other HFSE concentrations (i.e., from typical Nb-depleted arc basalts to rare high-Nb basalts) and the oceanic crust subducting beneath the arc system has been sampled by the Ocean Drilling Program. The investigation will employ various geochemical and isotopic tracers (e.g., REE, Nb/Ta, Ba/La, Pb/Ce, 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, 18O/16O) in order to fingerprint the behavior of many trace elements, particularly the HFSE, during the generation of arc lavas. Results of the study will also be useful for a general understanding of the source materials of lavas in the global arc system.