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| Titel |
ANPAR: a new analytical parameterization of CPO generation in the mantle |
| VerfasserIn |
Neil Goulding, Neil Ribe, Olivier Castelnau, Andrew Walker, James Wookey |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107609
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| Publikation (Nr.) |
 EGU/EGU2015-7317.pdf |
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| Zusammenfassung |
| Seismic anisotropy in the upper mantle is primarily due to the crystallographic preferred
orientation (CPO) of olivine crystals, and reflects the space- and time-dependence of the
deformation experienced by mantle rocks. Incorporating the generation of CPO into models
of mantle flow offers a powerful tool to link seismic observations with the process
of mantle convection. However, existing models (VPSC, Second Order, D-Rex,
etc.) for the evolution of CPO make predictions in good agreement with laboratory
experiments, but are too computationally intensive to be incorporated into 3-D mantle flow
codes, especially when the flow is time-dependent. Using the state-of-the-art Second
Order (SO) self-consistent model as our benchmark, we show that its predictions
of crystallographic spin as a function of crystal orientation can be parameterized
analytically in a surprisingly simple way that reduces the computational cost by orders of
magnitude. The parameterization allows for different strengths of the three dominant
olivine slip systems, as well as a macroscopic strain rate tensor having an arbitrary
orientation relative to the finite-strain ellipsoid that encodes the prior deformation
history. The parameterization agrees almost perfectly with the SO model (it fits its
predictions for CPO and crystallographic spin with a variance reduction > 99%), but with
a computational cost that is smaller by a factor 2-8 x104. We will illustrate the
predictions of the parameterization using three uniform deformations (uniaxial
compression, pure shear, simple shear) and for a corner-flow model of a spreading ridge. |
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