Carbonate-capped seamount subduction accelerates CO<sub>2</sub>-rich arc magma ascent.
basic_science · Level V
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- Record sourced from PubMed, PMID 42185278.
- Also identified by DOI 10.1038/s41467-026-71536-3.
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Abstract
Subduction transports carbon into Earth's interior, yet how subducted carbon influences arc magma ascent dynamics remains unclear. Here we combine volatile compositions of olivine-hosted melt inclusions with olivine diffusion chronometry at Pagan volcano (Mariana arc) to reveal a direct link between carbonate-capped seamount subduction and rapid magma ascent. Melt inclusions record high CO<sub>2</sub> contents (2000-6000 ppm), and magma storage near Moho depths (~20 km). Olivine zoning profiles constrain magma ascent from near-Moho to the surface on timescales of weeks to months. Elevated CaO/Al<sub>2</sub>O<sub>3</sub> ratios (>1) in erupted volcanics, heavy δ<sup>13</sup>C values (~0.5‰) in monitored volcanic gases, and the occurrence of seamount carbonate in the forearc mud volcano collectively point to subducted seamount carbonates as the dominant CO<sub>2</sub> source feeding Pagan magmatism. We propose that early CO<sub>2</sub> exsolution near the Moho generates overpressure that enables hydrous arc magmas to bypass crustal stalling. These results identify CO<sub>2</sub> as a key driver of rapid magma ascent in arcs and highlight carbonate-capped seamount subduction as an efficient pathway for deep carbon cycling.