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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 MaWVBvolcanic rocks; new geochemistry shows that the same processes characterized ~18–30 MaWVBmagmatism in Alaska. New40Ar/39Ar ages demonstrate thatWVBmagmatism 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 AlaskanWVBmagmatism occurred chiefly due to subduction and should be considered a volcanic arc (e.g. the Wrangell Arc). TheWVBprovides 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.
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Controls of Slab Subduction and Tearing on the Magmatism of Wrangell Volcanoes in South‐Central Alaska
Abstract This study integrates data from all broadband seismic stations in Alaska and northwestern Canada in 1999–2022 to construct a shear‐wave velocity model for south‐central Alaska and northwesternmost Canada, using ambient noise wave propagation simulation and inversion. Our model reveals three key features, including (a) the presence of the subducting Yakutat slab with apparent velocity reductions near the trench and within its flat segment, (b) two slab segments beneath the Wrangell volcanic field, differing in steepness, depth, and seismic velocity, and aligning spatially with the northwestern and southeastern volcano clusters, and (c) the existence of slab windows between the Yakutat and Wrangell slabs and between the northwestern and southeastern portions of the Wrangell slab. Our findings reinforce that the Wrangell volcanoes are predominantly influenced by subduction‐related magmatism. Furthermore, the two slab windows could have induced asthenospheric upwelling, contributing to the volcanism in the Wrangell clustered volcanoes.
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- PAR ID:
- 10586012
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 52
- Issue:
- 8
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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