Mantle Flow and Anisotropy in Subduction Zones: Modeling and Clustering of Olivine Textures

Abstract

Abstract The mantle near Earth's subduction zones endures intense deformation that generates anisotropic rock textures. These textures can be observed seismically and modeled geodynamically, but the complexity of this deformation makes analyses of these textures difficult. In this study, we apply time‐series clustering analysis to tracers within subduction models, allowing for the identification of regions in the subduction zone with common deformation histories and olivine crystallographic‐preferred orientation development. We compare olivine texture evolution predicted using different methods in both retreating and stationary‐trench settings. Our results reveal distinct variations in olivine texture, indicating that both seismic and viscous anisotropy can exhibit substantial heterogeneity within the mantle wedge, sub‐slab, and subducting plate regions. For retreating trenches, olivine textures are strongest in the mid‐depth mantle wedge region about 200 km away from the trench between 100 and 300 km depth. Our study shows that trench‐normal olivine a‐axis orientations dominate in the center of subduction zones. Toroidal flow around slab edges generates a mix of trench‐normal, trench‐parallel, and oblique fast seismic directions. Textures and anisotropy are stronger for the retreating trench model than for the stationary trench model since more deformation has been accumulated due to trench motion. These findings provide insights for interpreting seismic anisotropy in subduction zones and highlight the importance of considering texture heterogeneity, as characterized by clustering algorithms, when analyzing both geodynamic models and seismic observations of subduction zones.

Keywords

• olivine CPO
• anisotropy
• subduction
• numerical model
• clustering