LAUSR

Carbon recycling efficiency of arc (CREA) is an important parameter to assess the recycling of slab carbon into Earth's deep interior. Although previous studies observed variable degrees of recycled slab carbon at global arcs, the CREA value of any individual subduction zone has not been obtained due to the loose constraints on carbon budget in altered oceanic crust (AOC). Here, through estimates of carbon input by both sediments and AOC at DSDP Site 543 and recycled carbon output from major volcanoes in the Central‐Northern Lesser Antilles, we show an extremely efficient carbon recycling case, with the CREA value reaching 100±27%. Nearly complete slab carbon release at sub‐arc depth implies little carbon has been lost in the forearc region or subducted into the deep mantle in this subduction zone. Our results highlight strongly variable CREA on a global scale, which must be considered in the modeling of global deep carbon cycle.