A new study from the University of Washington’s ESS Non-Traditional Isotope Laboratory reveals a substantial, previously underappreciated contribution to arc magmas from melting at the base of the mantle wedge, the region above a subducting tectonic plate.

Led by PhD candidate Winnie Fan, the study used magnesium isotopes to trace these deep, water-rich melts. Models suggest that they can supply up to 50% of the magnesium in some arc magma sources. Published in Science Advances, the findings improve our understanding of how arc magmas form and help constrain Earth’s deep volatile cycle, which influences climate and habitability over geologic time.

For more information, contact Winnie Fan at . 

The UW co-authors are Fang-Zhen Teng and Yinbiao Peng. A full list of co-authors and funding is included in the paper.