Across-arc noble gas and halogen variations of slab-derived fluids in the Izu-Ogasawara subduction zone

Abstract

To verify whether and how slab-derived fluids may modify the composition of the mantle beneath subduction zones, we determined the noble gas and halogen compositions of olivines in arc lavas from the northern Izu-Ogasawara subduction zone and IODP sediments and basalts recovered from the northwestern margin of the Pacific plate.
Across arc variations in Ar isotope ratios and halogen compositions suggest that halogen-poor fluid associated with atmospheric noble gases may be predominantly released from the subducting slab beneath the arc, whilst halogen-rich fluid is released at greater depths and is a significant contributor to the magmas of some rear-arc volcanoes.