The role of crustal accretion variations in determining slab hydration at an Atlantic subduction zone

Allen, R. W., Collier, J. S., Henstock, T. J. and The VoiLA Consortium (2022) The role of crustal accretion variations in determining slab hydration at an Atlantic subduction zone. Journal of Geophysical Research: Solid Earth, 127 (8). ISSN 2169-9313

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Abstract

We present a 2D P-wave velocity model from the outer rise region of the Lesser Antilles island arc, the first wide-angle seismic study of outer rise processes at an Atlantic subduction zone. The survey consists of 46 OBS receivers over a 174 km profile with velocities resolved to 15 km below top basement. The final velocity model, produced through tomographic inversion, shows a clear decrease in the velocity of the lower crust and upper mantle of the incoming plate as it approaches the trench. We attribute this drop to outer rise bend-related hydration, similar to Pacific cases, but superimposed on spatial variations in hydration generated at the slow-spreading ridge axis. In thin, tectonically controlled crust formed under magma-poor spreading conditions the superposition of these sources of hydration results in compressional velocities as low as 6.5 km s-1 beneath the PmP reflector. In contrast, segments of crust interpreted as having formed under magma-rich conditions show velocity reductions and inferred hydrous alteration more like that observed in the Pacific. Hence, variations in the style of crustal accretion, which is observed on 50-100 km length scales both along and across isochrons, is a primary control over the distribution of water within the slab at Atlantic subduction systems. This heterogeneous pattern of water storage within the slab is likely further complicated by along strike variations in outer rise bending, subducting fracture zones and deformation at segment ends and may have important implications for our understanding of long-term patterns of hazard at Atlantic subduction systems.

Item Type: Article
Additional Information: Research Funding: Natural Environment Research Council. Grant Number: NE/K010743/1; Imperial College London
Uncontrolled Keywords: subduction,lesser antilles,outer rise bend faults,structure of oceanic crust,serpentinization,wide-angle seismic survey
Faculty \ School: Faculty of Science > School of Environmental Sciences
Related URLs:
Depositing User: LivePure Connector
Date Deposited: 08 Aug 2022 16:30
Last Modified: 22 Sep 2022 19:31
URI: https://ueaeprints.uea.ac.uk/id/eprint/87133
DOI: 10.1029/2022JB024349

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