A Spectral Directors Method for Modeling the Coupled Evolution of Flow and CPO in Polycrystalline Olivine
Abstract The crystallographic preferred orientation (CPO) of polycrystalline olivine affects both the viscous and seismic anisotropy of Earth's upper mantle with wide geodynamical implications. In this methods paper, we present a continuous field formulation of the popular directors method for...
Saved in:
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2024-12-01
|
| Series: | Geochemistry, Geophysics, Geosystems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2024GC011831 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1850243184999792640 |
|---|---|
| author | Nicholas M. Rathmann Klaus Mosegaard Ivanka M. O. Bekkevold David A. Lilien David J. Prior |
| author_facet | Nicholas M. Rathmann Klaus Mosegaard Ivanka M. O. Bekkevold David A. Lilien David J. Prior |
| author_sort | Nicholas M. Rathmann |
| collection | DOAJ |
| description | Abstract The crystallographic preferred orientation (CPO) of polycrystalline olivine affects both the viscous and seismic anisotropy of Earth's upper mantle with wide geodynamical implications. In this methods paper, we present a continuous field formulation of the popular directors method for modeling the strain‐induced evolution of olivine CPOs, assuming the activation of a single preferred crystal slip system. The formulation reduces the problem of CPO evolution to a linear matrix problem that can easily be integrated alongside large‐scale geodynamical flow models, and conveniently minimizes the degrees of freedom necessary to represent CPO fields. We validate the CPO model against existing deformation experiments and naturally deformed samples, as well as the popular discrete grain model D‐Rex. A numerical model of viscoplastic thermal convection is built to illustrate how flow and CPO evolution may be two‐way coupled, suggesting that CPO‐induced viscous anisotropy does not necessarily strongly affect convection time scales, boundary (lid) stresses, and seismic anisotropy, compared to isotropic viscoplastic rheologies. As a consequence, geodynamical modeling that relies on an isotropic rheology (one‐way coupling) might suffice for predicting seismic anisotropy under some circumstances. Finally, we discuss limitations and shortcomings of our method, such as representing D‐ and E‐type fabrics or modeling flows with mixed fabric types, and potential improvements such as accounting for the effect of dynamic recrystallization. |
| format | Article |
| id | doaj-art-579f5b3a5e754d0389178e569fa068c3 |
| institution | OA Journals |
| issn | 1525-2027 |
| language | English |
| publishDate | 2024-12-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj-art-579f5b3a5e754d0389178e569fa068c32025-08-20T02:00:03ZengWileyGeochemistry, Geophysics, Geosystems1525-20272024-12-012512n/an/a10.1029/2024GC011831A Spectral Directors Method for Modeling the Coupled Evolution of Flow and CPO in Polycrystalline OlivineNicholas M. Rathmann0Klaus Mosegaard1Ivanka M. O. Bekkevold2David A. Lilien3David J. Prior4Niels Bohr Institute University of Copenhagen Copenhagen DenmarkNiels Bohr Institute University of Copenhagen Copenhagen DenmarkNiels Bohr Institute University of Copenhagen Copenhagen DenmarkDepartment of Earth and Atmospheric Sciences Indiana University Bloomington IN USADepartment of Geology University of Otago Otago New ZealandAbstract The crystallographic preferred orientation (CPO) of polycrystalline olivine affects both the viscous and seismic anisotropy of Earth's upper mantle with wide geodynamical implications. In this methods paper, we present a continuous field formulation of the popular directors method for modeling the strain‐induced evolution of olivine CPOs, assuming the activation of a single preferred crystal slip system. The formulation reduces the problem of CPO evolution to a linear matrix problem that can easily be integrated alongside large‐scale geodynamical flow models, and conveniently minimizes the degrees of freedom necessary to represent CPO fields. We validate the CPO model against existing deformation experiments and naturally deformed samples, as well as the popular discrete grain model D‐Rex. A numerical model of viscoplastic thermal convection is built to illustrate how flow and CPO evolution may be two‐way coupled, suggesting that CPO‐induced viscous anisotropy does not necessarily strongly affect convection time scales, boundary (lid) stresses, and seismic anisotropy, compared to isotropic viscoplastic rheologies. As a consequence, geodynamical modeling that relies on an isotropic rheology (one‐way coupling) might suffice for predicting seismic anisotropy under some circumstances. Finally, we discuss limitations and shortcomings of our method, such as representing D‐ and E‐type fabrics or modeling flows with mixed fabric types, and potential improvements such as accounting for the effect of dynamic recrystallization.https://doi.org/10.1029/2024GC011831CPOfabricviscous anisotropyseismic anisotropymantle flowthermal convection |
| spellingShingle | Nicholas M. Rathmann Klaus Mosegaard Ivanka M. O. Bekkevold David A. Lilien David J. Prior A Spectral Directors Method for Modeling the Coupled Evolution of Flow and CPO in Polycrystalline Olivine Geochemistry, Geophysics, Geosystems CPO fabric viscous anisotropy seismic anisotropy mantle flow thermal convection |
| title | A Spectral Directors Method for Modeling the Coupled Evolution of Flow and CPO in Polycrystalline Olivine |
| title_full | A Spectral Directors Method for Modeling the Coupled Evolution of Flow and CPO in Polycrystalline Olivine |
| title_fullStr | A Spectral Directors Method for Modeling the Coupled Evolution of Flow and CPO in Polycrystalline Olivine |
| title_full_unstemmed | A Spectral Directors Method for Modeling the Coupled Evolution of Flow and CPO in Polycrystalline Olivine |
| title_short | A Spectral Directors Method for Modeling the Coupled Evolution of Flow and CPO in Polycrystalline Olivine |
| title_sort | spectral directors method for modeling the coupled evolution of flow and cpo in polycrystalline olivine |
| topic | CPO fabric viscous anisotropy seismic anisotropy mantle flow thermal convection |
| url | https://doi.org/10.1029/2024GC011831 |
| work_keys_str_mv | AT nicholasmrathmann aspectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine AT klausmosegaard aspectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine AT ivankamobekkevold aspectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine AT davidalilien aspectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine AT davidjprior aspectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine AT nicholasmrathmann spectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine AT klausmosegaard spectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine AT ivankamobekkevold spectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine AT davidalilien spectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine AT davidjprior spectraldirectorsmethodformodelingthecoupledevolutionofflowandcpoinpolycrystallineolivine |