Modeling olivine CPO evolution with complex deformation histories: Implications for the interpretation of seismic anisotropy in the mantle

Yuval Boneh (1) , Luiz Morales (2) , Edouard Kaminski (3) , Philip Skemer (1)

1 Department of Earth and Planetary Sciences [St Louis]
2 GFZ - German Research Centre for Geosciences - Helmholtz-Centre Potsdam
3 IPGP - Institut de Physique du Globe de Paris

Relating seismic anisotropy to mantle flow requires detailed understanding of the development and evolution of olivine crystallographic preferred orientation (CPO). Recent experimental and field studies have shown that olivine CPO evolution depends strongly on the integrated deformation history, which may lead to differences in how the corresponding seismic anisotropy should be interpreted. In this study, two widely used numerical models for CPO evolutionD-Rex and VPSCare evaluated to further examine the effect of deformation history on olivine texture and seismic anisotropy. Building on previous experimental work, models are initiated with several different CPOs to simulate unique deformation histories. Significantly, models initiated with a preexisting CPO evolve differently than the CPOs generated without preexisting texture. Moreover, the CPO in each model evolves differently as a function of strain. Numerical simulations are compared to laboratory experiments by Boneh and Skemer (2014). In general, the D-Rex and VPSC models are able to reproduce the experimentally observed CPOs, although the models significantly over-estimate the strength of the CPO and in some instances produce different CPO from what is observed experimentally. Based on comparison with experiments, recommended parameters for D-Rex are: M*=10, *=5, and =0.3, and for VPSC: =10-100. Numerical modeling confirms that CPO evolution in olivine is highly sensitive to the details of the initial CPO, even at strains greater than 2. These observations imply that there is a long transient interval of CPO realignment which must be considered carefully in the modeling or interpretation of seismic anisotropy in complex tectonic settings.

Mots clés: olivine; CPO; deformation history; D-Rex; VPSC; numerical models

Domaines: Géophysique [physics.geo-ph]

Yuval Boneh, Luiz Morales, Edouard Kaminski, Philip Skemer. Modeling olivine CPO evolution with complex deformation histories: Implications for the interpretation of seismic anisotropy in the mantle. Geochemistry, Geophysics, Geosystems, 2015, 16 (10), pp.3436-3455. ⟨10.1002/2015GC005964⟩. ⟨insu-02929133⟩