Subduction erosion, or scraping off of the continental crust by subducting oceanic lithosphere, is an important tectonic process along parts of the Andean convergent plate boundary. Estimated rates of subduction erosion increase northward north of the southem Andes, due to decreasing subduction angle and decreasing sediment supply to the trench. West of the central Andes subduction erosion may remove as much as 535 km3 of crust per 1 km of trench per 1 m.y., or 7 vol% of the subducting oceanic lithosphere. The higher 87Sr/86Sr ratios of mafic magmas erupted north of the southern Andes may be explained by the higher rates of subduction erosion and increased amounts of contamination of the sub-arc mantle magma source.

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