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dc.contributor.authorNedimovic, Mladen R.  Concept link
dc.contributor.authorCarbotte, Suzanne M.  Concept link
dc.contributor.authorDiebold, John B.  Concept link
dc.contributor.authorHarding, Alistair J.  Concept link
dc.contributor.authorCanales, J. Pablo  Concept link
dc.contributor.authorKent, Graham M.  Concept link
dc.date.accessioned2010-04-21T13:36:12Z
dc.date.available2010-04-21T13:36:12Z
dc.date.issued2008-09-30
dc.identifier.citationGeochemistry Geophysics Geosystems 9 (2008): Q09006en_US
dc.identifier.urihttps://hdl.handle.net/1912/3282
dc.descriptionAuthor Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 9 (2008): Q09006, doi:10.1029/2008GC002085.en_US
dc.description.abstractRecent P wave velocity compilations of the oceanic crust indicate that the velocity of the uppermost layer 2A doubles or reaches ∼4.3 km/s found in mature crust in <10 Ma after crustal formation. This velocity change is commonly attributed to precipitation of low-temperature alteration minerals within the extrusive rocks associated with ridge-flank hydrothermal circulation. Sediment blanketing, acting as a thermal insulator, has been proposed to further accelerate layer 2A evolution by enhancing mineral precipitation. We carried out 1-D traveltime modeling on common midpoint supergathers from our 2002 Juan de Fuca ridge multichannel seismic data to determine upper crustal structure at ∼3 km intervals along 300 km long transects crossing the Endeavor, Northern Symmetric, and Cleft ridge segments. Our results show a regional correlation between upper crustal velocity and crustal age. The measured velocity increase with crustal age is not uniform across the investigated ridge flanks. For the ridge flanks blanketed with a sealing sedimentary cover, the velocity increase is double that observed on the sparsely and discontinuously sedimented flanks (∼60% increase versus ∼28%) over the same crustal age range of 5–9 Ma. Extrapolation of velocity-age gradients indicates that layer 2A velocity reaches 4.3 km/s by ∼8 Ma on the sediment blanketed flanks compared to ∼16 Ma on the flanks with thin and discontinuous sediment cover. The computed thickness gradients show that layer 2A does not thin and disappear in the Juan de Fuca region with increasing crustal age or sediment blanketing but persists as a relatively low seismic velocity layer capping the deeper oceanic crust. However, layer 2A on the fully sedimented ridge-flank sections is on average thinner than on the sparsely and discontinuously sedimented flanks (330 ± 80 versus 430 ± 80 m). The change in thickness occurs over a 10–20 km distance coincident with the onset of sediment burial. Our results also suggest that propagator wakes can have atypical layer 2A thickness and velocity. Impact of propagator wakes is evident in the chemical signature of the fluids sampled by ODP drill holes along the east Endeavor transect, providing further indication that these crustal discontinuities may be sites of localized fluid flow and alteration.en_US
dc.description.sponsorshipThis research was supported by National Science Foundation grants OCE-00-02488, OCE-00-02551, and OCE-00- 02600.en_US
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen_US
dc.publisherAmerican Geophysical Unionen_US
dc.relation.urihttps://doi.org/10.1029/2008GC002085
dc.subjectUpper crustal evolutionen_US
dc.subjectMultichannel seismicsen_US
dc.subjectTraveltime modelingen_US
dc.subjectReflection imagingen_US
dc.subjectJuan de Fuca ridge flanksen_US
dc.titleUpper crustal evolution across the Juan de Fuca ridge flanksen_US
dc.typeArticleen_US
dc.identifier.doi10.1029/2008GC002085


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