Effects of Composite Rheology on Plate‐Like Behavior in Global‐Scale Mantle Convection

• Published in: Geophysical research letters 2023-08, Vol.50 (16), p.n/a
• Main Authors: Arnould, Maëlis, Rolf, Tobias, Manjón‐Cabeza Córdoba, Antonio
• Format: Article
• Language: English
• Subjects: Anisotropy; Asthenosphere; composite rheology; Convection; Deformation; Deformation mechanisms; Diffusion; Dislocation; Earth; Earth mantle; Earth surface; Environmental Sciences; geodynamic modeling; Lithosphere; Mantle convection; mantle rheology; Mathematical models; Numerical models; Plate tectonics; Plates (tectonics); Plumes; Rheological properties; Rheology; Rock deformation; Solifluction; Strength; Subduction (geology); Surface dynamics; Tectonics; Temporal distribution; Upper mantle; Viscosity; Yield strength; Yield stress
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL104146

Earth's upper mantle rheology controls lithosphere‐asthenosphere coupling and thus surface tectonics. Rock deformation experiments and seismic anisotropy measurements indicate that composite rheology (co‐existing diffusion and dislocation creep) occurs in the Earth's uppermost mantle, potentially affecting convection and surface tectonics. Here, we investigate how the spatio‐temporal distribution of dislocation creep in an otherwise diffusion‐creep‐controlled mantle impacts the planform of convection and the planetary tectonic regime as a function of the lithospheric yield strength in numerical models of mantle convection self‐generating plate‐like tectonics. The low upper‐mantle viscosities caused by zones of substantial dislocation creep produce contrasting effects on surface dynamics. For strong lithosphere (yield strength > 35 MPa), the large lithosphere‐asthenosphere viscosity contrasts promote stagnant‐lid convection. In contrast, the increase of upper mantle convective vigor enhances plate mobility for lithospheric strength