The Alaska Wrangell Arc: ~30 Ma of subduction‐related magmatism along a still active arc‐transform junction

• Published in: Terra Nova
• Main Authors: Brueseke, Matthew E., Benowitz, Jeffrey A., Trop, Jeffrey M., Davis, Kailyn N., Berkelhammer, Samuel E., Layer, Paul W., Morter, Bethany K.
• Other Authors: Division of Earth Sciences, National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2019
• Subjects: Canada; Yakutat; Alaska
• Online Access: http://dx.doi.org/10.1111/ter.12369; https://onlinelibrary.wiley.com/doi/pdf/10.1111/ter.12369; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/ter.12369; https://onlinelibrary.wiley.com/doi/am-pdf/10.1111/ter.12369

Abstract The Oligocene to Present Wrangell Volcanic Belt ( WVB ) extends for ~500 km across south‐central Alaska (USA) into Canada at a volcanic arc‐transform junction. Previously, geochemistry documented mantle wedge and slab‐edge melting in <12 Ma WVB volcanic rocks; new geochemistry shows that the same processes characterized ~18–30 Ma WVB magmatism in Alaska. New 40 Ar/ 39 Ar ages demonstrate that WVB magmatism in Alaska initiated at ~30 Ma due to flat‐slab subduction of the Yakutat microplate and that the dextral Totschunda fault was active at this time. Our results, together with prior studies, show that Alaskan WVB magmatism occurred chiefly due to subduction and should be considered a volcanic arc (e.g. the Wrangell Arc). The WVB provides a long‐term geological record of subduction, strike‐slip and magmatism. Slab‐edge upwelling, flat‐slab defocused fluid‐flux and faults acting as magma conduits are likely responsible for the exceptionally large volcanoes and high eruption rates of the Wrangell Arc.