Effects of crystal preferred orientation on upper-mantle flow near plate boundaries: rheologic feedbacks and seismic anisotropy

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dc.contributor.author BLACKMAN, D.K
ensam.hal.laboratories
  121317 Scripps Institution of Oceanography [SIO]
dc.contributor.author BOYCE, D.E
ensam.hal.laboratories
  99874 Cornell University
dc.contributor.author CASTELNAU, O
ensam.hal.laboratories
  86289 Procédés et Ingénierie en Mécanique et Matériaux [Paris] [PIMM]
dc.contributor.author DAWSON, P.R
ensam.hal.laboratories
  99874 Cornell University
dc.contributor.author LASKE, G
ensam.hal.laboratories
  121317 Scripps Institution of Oceanography [SIO]
dc.date.accessioned 2018-01-05T14:56:26Z
dc.date.available 2018-01-09T01:27:40Z
dc.date.issued 2017
dc.date.submitted 2017-11-21T20:02:37Z
dc.identifier.uri http://hdl.handle.net/10985/12467
dc.description.abstract Insight into upper-mantle processes can be gained by linking flow-induced mineral alignment to regional deformation and seismic anisotropy patterns. Through a series of linked micro–macro scale numerical experiments, we explore the rheologic effects of crystal preferred orientation (CPO) and evaluate the magnitude of possible impacts on the pattern of flow and associated seismic signals for mantle that includes a cooling, thickening young oceanic lithosphere. The CPO and associated anisotropic rheology, computed by a micromechanical polycrystal model, are coupled with a large scale flow model (Eulerian Finite Element method) via a local viscosity tensor field, which quantifies the stress:strain rate response of a textured polycrystal. CPO is computed along streamlines throughout the model space and the corresponding viscosity tensor field at each element defines the local properties for the next iteration of the flow field. Stable flow and CPO distributions were obtained after several iterations for the two dislocation glide cases tested: linear and nonlinear stress:strain rate polycrystal behaviour. The textured olivine polycrystals are found to have anisotropic viscosity tensors in a significant portion of the model space. This directional dependence in strength impacts the pattern of upper-mantle flow. For background asthenosphere viscosity of ∼1020 Pa s and a rigid lithosphere, the modification of the corner flow pattern is not drastic but the change could have geologic implications. Feedback in the development of CPO occurs, particularly in the region immediately below the base of the lithosphere. Stronger fabric is predicted below the flanks of a spreading centre for fully coupled, power-law polycrystals than was determined using prior linear, intermediate coupling polycrystal models. The predicted SKS splitting is modestly different (∼0.5 s) between the intermediate and fully coupled cases for oceanic plates less than 20 Myr old. The magnitude of azimuthal anisotropy for surface waves, on the other hand, is predicted to be twice as large for fully coupled power-law flow/polycrystals than for linear, intermediate coupled flow/polycrystal models. en
dc.language.iso en
dc.publisher Advance Access publication
dc.rights Post-print
dc.subject Mantle processes; Seismic anisotropy; Rheology: mantle. en
dc.title Effects of crystal preferred orientation on upper-mantle flow near plate boundaries: rheologic feedbacks and seismic anisotropy en
ensam.hal.id hal-01676438 *
ensam.hal.status accept *
ensam.embargo.terms 2018-01-09
dc.identifier.doi 10.1093/gji/ggx251
dc.typdoc Articles dans des revues avec comité de lecture
dc.localisation Centre de Paris
dc.subject.hal Sciences de l'ingénieur: Matériaux
dc.subject.hal Sciences de l'ingénieur: Mécanique
ensam.workflow.submissionConsumer updateFiles *
ensam.audience Internationale
ensam.page 1481–1493
ensam.journal Geophysical Journal International
ensam.volume 210
ensam.peerReviewing Oui

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