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Limited Mantle Hydration by Bending Faults at the Middle America Trench

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dc.contributor.authorMiller, Nathaniel C.en
dc.contributor.authorLizarralde, Danielen
dc.contributor.authorCollins, John A.en
dc.contributor.authorHolbrook, W. Stevenen
dc.contributor.authorVan Avendonk, Harm J. A.en
dc.contributor.departmentGeosciencesen
dc.date.accessioned2021-07-16T15:58:03Zen
dc.date.available2021-07-16T15:58:03Zen
dc.date.issued2021-01en
dc.description.abstractSeismic anisotropy measurements show that upper mantle hydration at the Middle America Trench (MAT) is limited to serpentinization and/or water in fault zones, rather than distributed uniformly. Subduction of hydrated oceanic lithosphere recycles water back into the deep mantle, drives arc volcanism, and affects seismicity at subduction zones. Constraining the extent of upper mantle hydration is an important part of understanding many fundamental processes on Earth. Substantially reduced seismic velocities in tomography suggest that outer rise plate-bending faults provide a pathway for seawater to rehydrate the slab mantle just prior to subduction. Estimates of outer-rise hydration based on tomograms vary significantly, with some large enough to imply that, globally, subduction has consumed more than two oceans worth of water during the Phanerozoic. We found that, while the mean upper mantle wavespeed is reduced at the MAT outer rise, the amplitude and orientation of inherited anisotropy are preserved at depths >1 km below the Moho. At shallower depths, relict anisotropy is replaced by slowing in the fault-normal direction. These observations are incompatible with pervasive hydration but consistent with models of wave propagation through serpentinized fault zones that thin to 1 km below Moho. Confining hydration to fault zones reduces water storage estimates for the MAT upper mantle from similar to 3.5 wt% to <0.9 wt% H(2)0. Since the intermediate thermal structure in the similar to 24 Myr-old MAT slab favors serpentinization, limited hydration suggests that fault mechanics are the limiting factor, not temperatures. Subducting mantle may be similarly dry globally.en
dc.description.adminPublic domain – authored by a U.S. government employeeen
dc.description.notesWe are grateful for the hard work and dedication of the technicians, crews, officers, and science party of R/V Langseth cruise MGL0807, who overcame many obstacles during Langseth's first science program, and also Trish Gregg and everyone aboard R/V New Horizon cruise TC2NH, which handled OBS operations. The OBS were provided and supported by the US Ocean Bottom Seismograph Instrument Pool (http://www.obsip.org) facilities at the Woods Hole Oceanographic Institution and the Scripps Institution of Oceanography. We thank D. Shillington, S. Naif, F. Klein, and U. ten Brink for many productive discussions and J. Kluesner, C. Ruppel, A. Trehu, and J. Korenaga for reviews of this manuscript.en
dc.description.sponsorshipUS Ocean Bottom Seismograph Instrument Pool facilities at the Woods Hole Oceanographic Institution; Scripps Institution of OceanographyUniversity of California Systemen
dc.description.versionPublished versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.1029/2020JB020982en
dc.identifier.eissn2169-9356en
dc.identifier.issn2169-9313en
dc.identifier.issue1en
dc.identifier.othere2020JB020982en
dc.identifier.urihttp://hdl.handle.net/10919/104189en
dc.identifier.volume126en
dc.language.isoenen
dc.rightsPublic Domainen
dc.rights.urihttp://creativecommons.org/publicdomain/mark/1.0/en
dc.subjectouter&#8208en
dc.subjectrise hydrationen
dc.subjectupper mantle anisotropyen
dc.subjectupper mantle hydrationen
dc.titleLimited Mantle Hydration by Bending Faults at the Middle America Trenchen
dc.title.serialJournal of Geophysical Research-Solid Earthen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.dcmitypeStillImageen

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