SUBDUCTION VELOCITY CONTROLS ON ARC MAGMATISM ALONG LONG-LIVED NE ASIA CORDILLERAN ARC SYSTEM

The general link between subduction and arc magmatism has been widely accepted since the plate tectonics revolution; however, the evolutions in magmatic arc tempos and chemistry (e.g., wt.% SiO₂) are still not fully explained. The arc crust thickness was considered a primary driver for the flare-ups and lulls, and chemical fractionation of the magmatism in long-lived cordillera arc systems, while the role of the subducting slab was not well-quantified.

This study explores the subduction velocity controls on magmatism along the 100 ~ 0 Ma NE Asia continental arc. We used statistical analysis on two paired geologic/plate tectonic datasets: (1) a large (n>500) NE Asian magmatic database of published and unpublished U-Pb zircon ages and geochemistry; and (2) plate convergence velocity extracted from a recently published, digital, fully-kinematic Eurasia-Pacific plate tectonic reconstruction (Wu et al., 2022 EPSL). The plate reconstruction model reveals ultrafast Izanagi subduction (12 to 24 cm/yr) during 100-52 Ma in contrast to slower Pacific subduction (< 8 cm/yr) during 52-0 Ma along the NE Asian margin. Comparison to NE Asia magmatism reveals the igneous rocks generated during the 100-52 Ma ultrafast subduction show high magmatic areal addition rates, high % SiO₂ (mean 66-70 %), and enriched Nd isotopic ratios (-15 to +2). In comparison, igneous rocks generated during the slower 52-0 Ma subduction were characterized by lower magmatic rates, SiO₂ (mean 56-63 %), and more depleted Nd isotopic ratios (-5 to +10). Linear statistical analysis shows significant correlations between subduction velocity and magmatic geochemistry with p-values lower than 0.05. We discuss the possible contribution of ultrafast subduction (>12 cm/yr) on high-flux, high-silica magmatism relative to arcs developed above more typical subduction velocities (<10 cm/yr), with implications from numerical subduction zone modeling and the modern Tonga-Kermadec arc that has along-strike subduction velocity variate from 6 to 23 cm/yr.