As an important subduction component, altered oceanic crust (AOC) is widely distributed on the oceanic subducting slab and may contribute significantly to the chemistry of arc magmas. However, identifying this contribution in arc magmas is challenging because AOC is not as enriched in incompatible elements as sediments, nor does it have as high H2O concentrations as do serpentinites. Therefore, it is necessary to find a sensitive tracer for subducted AOC.
