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The Alaska Wrangell Arc: ~30 Ma of subduction‐related magmatism along a still active arc‐transform junction
Author(s) -
Brueseke Matthew E.,
Benowitz Jeffrey A.,
Trop Jeffrey M.,
Davis Kailyn N.,
Berkelhammer Samuel E.,
Layer Paul W.,
Morter Bethany K.
Publication year - 2019
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/ter.12369
Subject(s) - geology , magmatism , subduction , volcano , mantle wedge , mantle (geology) , slab , geochemistry , volcanic arc , seismology , volcanic rock , island arc , geophysics , tectonics
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.