Evolution of magmatic systems in a nascent subduction zone: the example of Izu-Bonin-Mariana arc (IODP expedition 352)

• Applicants: Professor Dr. Francois Holtz; Professorin Dr.-Ing. Monika Sester
• Subject Area: Geology ; Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565988243

The Izu-Bonin-Mariana (IBM) fore-arc is one of the rare natural examples allowing us to describe the geological processes during the initiation of a subduction zone. The project aims to track the evolution of the magma plumbing systems during the onset of subduction, based on the systematic analysis of volcanic rocks from the Izu-Bonin-Mariana (IBM) fore-arc, drilled during IODP Expedition 352. A large number of volcanic samples (basalts and boninites) are available and can be used to unravel the evolution of P-T-fO2-aH2O conditions in magma reservoirs. The crystallization conditions in the magma reservoirs will be constrained using thermobarometers, based on the compositions of coexisting magmatic phases, and by applying thermodynamic models predicting crystallization sequences and mineral compositions (using MELTS and COMAGMAT). Time scales of magmatic processes will be estimated by interpreting compositional zoning using diffusion chronometry. Considering the large number of samples to be investigated, our approach will combine novel Deep Learning (DL) techniques and petrology for characterizing thin sections of volcanic rocks, allowing us to process automatically large datasets obtained by backscattered electron (BSE) images. Information on textural observations (mineral populations), thermobarometric estimations, and time scales of magmatic processes will be combined to describe the evolution of the magma plumbing systems in a nascent subduction zone, from fore arc basalts generated in the very early stage to high silica boninites representing an advanced stage of the subduction process. In particular, the results will allow us to test whether the depth of magma reservoirs, the frequency of magma recharge, the melt water content and oxygen fugacity increase with time. The importance of crystal fractionation and magma mixing/mingling on differentiation processes will be evaluated for the different magmatic stages.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 527: Infrastructure area - International Ocean Drilling Programme³ (IODP³)
• Co-Investigator: Renat Almeev, Ph.D.