Generation of carbonated peridotite melts via biogenic sediment recycling in modern subduction zones.

Abstract

The subduction of carbonate-rich biogenic sediments influences Earth's carbon cycle and regulates long-term climate. Yet, the processes controlling their behavior at the subduction interface remain debated. Here, we investigate the role of carbonate subduction through the petrogenesis of Quaternary rear-arc monogenetic volcanoes in Colombia. These volcanoes display unusual compositions resembling intraplate carbonated peridotite melts and experimental melts from peridotite + CO₂ systems. Their geochemistry reflects an anomalous mantle source modified by subducted sediments from the Panama Basin, a large-scale region of high primary productivity and carbonate accumulation. However, pristine subducted sediments alone cannot explain the full compositional range of rear-arc Colombian lavas. Instead, we propose that sediment partial melting beneath the arc front produces carbonate- and apatite-rich restites that act as a recycled carbonated component, contributing to mantle chemical heterogeneity. This model helps explain the geochemical diversity of mantle-derived intraplate lavas and establishes a direct link between biogeochemical cycles, subduction, and the evolution of the solid Earth.