| Title: |
Pressure-dependent large-scale seismic anisotropy induced by non-Newtonian mantle flow |
| Authors: |
Magali, John Keith, K; Ledoux, E, E; Thomas, C; Capdeville, Yann; Merkel, Sébastien |
| Contributors: |
Unité Matériaux et Transformations - UMR 8207 (UMET); Centrale Lille-Institut de Chimie - CNRS Chimie (INC-CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE); University of Utah; Westfälische Wilhelms-Universität Münster = University of Münster = Université de Münster Münster, Allemagne (WWU); Laboratoire de Planétologie et Géosciences UMR_C 6112 (LPG); Le Mans Université (UM)-Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST); Nantes Université - pôle Sciences et technologie; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Sciences et technologie; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ); DFG LASSIE project (TH1530/24-1); ANR-17-CE31-0025,TIMEleSS,Transformations de phase, microstructures, et leur signatures sismiques dans le manteau terrestre(2017) |
| Source: |
ISSN: 0956-540X. |
| Publisher Information: |
CCSD; Oxford University Press (OUP) |
| Publication Year: |
2024 |
| Collection: |
Université de Nantes: HAL-UNIV-NANTES |
| Subject Terms: |
Seismic discontinuities; Seismic anisotropy; Phase transitions; Composition and structure of the mantle; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] |
| Description: |
International audience ; Observations of large-scale seismic anisotropy can be used as a marker for past and current deformation in the Earth’s mantle. Nonetheless, global features such as the decrease of the strength of anisotropy between ∼150 and 410 km in the upper mantle and weaker anisotropy observations in the transition zone remain ill-understood. Here, we report a proof of concept method that can help understand anisotropy observations by integrating pressure-dependent microscopic flow properties in mantle minerals particularly olivine and wadsleyite into geodynamic simulations. The model is built against a plate-driven semi-analytical corner flow solution underneath the oceanic plate in a subduction setting spanning down to 660 km depth with a non-Newtonian n = 3 rheology. We then compute the crystallographic preferred orientation (CPO) of olivine aggregates in the upper mantle (UM), and wadsleyite aggregates in the upper transition zone (UTZ) using a viscoplastic self-consistent (VPSC) method, with the lower transition zone (LTZ, below 520 km) assumed isotropic. Finally, we apply a tomographic filter that accounts for finite-frequency seismic data using a fast-Fourier homogenization algorithm, with the aim of providing mantle models comparable with seismic tomography observations. Our results show that anisotropy observations in the UM can be well understood by introducing gradual shifts in strain accommodation mechanism with increasing depths induced by a pressure-dependent plasticity model in olivine, in contrast with simple A-type olivine fabric that fails to reproduce the decrease in anisotropy strength observed in the UM. Across the UTZ, recent mineral physics studies highlight the strong effect of water content on both wadsleyite plastic and elastic properties. Both dry and hydrous wadsleyite models predict reasonably low anisotropy in the UTZ, in agreement with observations, with a slightly better match for the dry wadsleyite models. Our calculations show that, despite the relatively primitive ... |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| DOI: |
10.1093/gji/ggae165 |
| Availability: |
https://hal.science/hal-04670847; https://hal.science/hal-04670847v1/document; https://hal.science/hal-04670847v1/file/Magali_2024_GJI.pdf; https://doi.org/10.1093/gji/ggae165 |
| Rights: |
info:eu-repo/semantics/OpenAccess |
| Accession Number: |
edsbas.95C94EB9 |
| Database: |
BASE |