Heterogeneity of volatile sources along the Halmahera arc, Indonesia

The parallel Halmahera and Sangihe arcs in eastern Indonesia are sites of active arc-arc collision considerable interest developing understanding the geodynamics geochemistry subduction zones. Owing to comparative remoteness region, few ground-based studies volcanoes have been undertaken. Here, we report integrate gas measurements (isotope) geochemical analyses lava samples for Dukono, Ibu, Gamkonora, Gamalama, Makian arc. Summing fluxes all five indicates arc-scale emission budgets H2O, CO2, SO2, H2S, H2 96,300 ± 27,000, 2093 450, 944 400, 79 20, 15 4 Mg/d, respectively. Dukono is greatest source SO2 H2, while Ibu emits most H2O H2S. Both Gamalama significant CO2 sources. (farthest from trench) releases CO2-poor gas. Geochemical isotopic recent ejecta emphasize role high fluid mantle wedge, necessary partial melting depleted mantle. Pb, Nd, Sr isotope ratios, combined with Ba/Nd, Zr/Nd, Ba/Th, Zr/Nb provide evidence compositional variability along arc, indicate decreasing subducted sediment contribution south (Makian, Gamalama) north (Gamkonora, Dukono). Additionally, fluids formed by dehydration altered crust become prominent at northern volcanoes. Isotopic Ba/Nb ratios Neogene Quaternary sources compared current magmas further evolution magma genesis since Neogene.