Testing the Slab Connection: A Beryllium Isotope Tracer Study in the Trans-Mexican Volcanic Belt

'Convergent plate margins' are major interfaces of the solid Earth geochemical cycle that are fundamental to the formation and maintenance of habitable Earth. At convergent plate margins, a kilometer-thick lithospheric plate consisting of the Earth's crust and uppermost mantle is drawn - or subducted - beneath another lithospheric plate. At around 80-140 kilometers depth, the subducted plate releases volatile-rich material and 'recycles' it back to the Earth's surface via highly explosive, volatile-rich volcanism that forms chains of volcanoes aligned in arcs. On human time scales, eruptions of such single arc volcanoes have caused deadly climate perturbations (e.g. Tambora in 1815) and tsunamis (e.g. Krakatoa in 1883). Hence, understanding how arc volcanism is related to the material transfer from slab remains at the core of geoscience research. In such studies, the cosmogenic isotope 10Be, plays a pivotal role, because it is a unique, geochemical tracer that unambiguously identifies material recycled from slab material. In addition to the important scientific impact of this work, this work impacts society by fostering international collaboration between the U.S. and Mexico, and it also supports students at Columbia. Results from this project will also be incorporated into course curricula.

Recent analytical advances have much improved the detection limit of 10Be in arc volcanic rocks, now allowing for integrating critical volcanic rock series from convergent margins that could not be studied previously. In this project, the 10Be tracer will be further explored and tested through a study in the Transmexican Volcanic Belt (TMVB). The TMVB is a major convergent margin which is well-known for historic eruptions that produced an unusually broad spectrum of volcanic rocks in close temporal and spatial association. While previous geochemical studies showed that these volcanic rocks have direct bearing on the material recycling from slab, crucial details of material transfer (how? how much? how fast?) remain contested. A selected set of well-studied samples from the central (Popocatepetl volcano and surrounding) and western (Colima volcano and surrounding) TMVB will be analysed for 10Be in order to test current hypotheses of subduction recycling. Overall, the project will provide new constraints on the connectivity between slab subduction and arc volcanism and its role in regulating the longterm evolution and maintenance of habitable Earth.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.