Subduction geometry beneath south central Alaska and its relationship to volcanism

Abstract

AbstractThe southern Alaskan margin captures a transition between compression and strike‐slip‐dominated deformation, accretion of the overthickened Yakutat terrane, termination of Aleutian arc magmatism, and the enigmatic Wrangell Volcanic Field. The extent of subduction and mantle structure below this region is uncertain, with important implications for volcanism. We present compressional and shear wave mantle velocity models below south central Alaska that leverage a new seismometer deployment to produce the most complete image of the subducting Pacific‐Yakutat plate to date. We image a steeply dipping slab extending below central Alaska to >400 km depth, which abruptly terminates east of ~145°W. There is no significant slab anomaly beneath the nearby Wrangell volcanoes. A paucity of volcanism is observed above the subducting Yakutat terrane, but the slab structure below 150 km depth and Wadati‐Benioff zone here are similar to those along the Aleutian‐Alaska arc. Features of the mantle wedge or overlying lithosphere are thus responsible for the volcanic gap.