The effect of deformation history on the evolution of olivine CPO

Boneh, Y.; Skemer, Philip

doi:10.1016/j.epsl.2014.09.018

Cited by 60 publications

(89 citation statements)

References 66 publications

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“…Measurements of seismic anisotropy provide a means to learn about oceanic plate formation and mantle flow. This is possible because the evolution of lithospheric anisotropy is sensitive to a variety of factors including preexisting mantle fabric (Boneh & Skemer, ; Skemer et al, ), the amount of strain the lithosphere experiences (e.g., Hedjazian & Kaminski, ; Ribe, ; Zhang & Karato, ), the magnitude of shear strain relative to the rate of rotation of the strain axes (Kaminski & Ribe, ), and the presence of melt during deformation (Hansen et al, ; Qi et al, ). At the same time, this variety of sensitivities can make the interpretation of anisotropy difficult.…”

Section: Discussionmentioning

confidence: 99%

Azimuthal Seismic Anisotropy of 70‐Ma Pacific‐Plate Upper Mantle

et al. 2019

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Plate formation and evolution processes are predicted to generate upper mantle seismic anisotropy and negative vertical velocity gradients in oceanic lithosphere. However, predictions for upper mantle seismic velocity structure do not fully agree with the results of seismic experiments. The strength of anisotropy observed in the upper mantle varies widely. Further, many refraction studies observe a fast direction of anisotropy rotated several degrees with respect to the paleospreading direction, suggesting that upper mantle anisotropy records processes other than 2‐D corner flow and plate‐driven shear near mid‐ocean ridges. We measure 6.0 ± 0.3% anisotropy at the Moho in 70‐Ma lithosphere in the central Pacific with a fast direction parallel to paleospreading, consistent with mineral alignment by 2‐D mantle flow near a mid‐ocean ridge. We also find an increase in the strength of anisotropy with depth, with vertical velocity gradients estimated at 0.02 km/s/km in the fast direction and 0 km/s/km in the slow direction. The increase in anisotropy with depth can be explained by mechanisms for producing anisotropy other than intrinsic effects from mineral fabric, such as aligned cracks or other structures. This measurement of seismic anisotropy and gradients reflects the effects of both plate formation and evolution processes on seismic velocity structure in mature oceanic lithosphere, and can serve as a reference for future studies to investigate the processes involved in lithospheric formation and evolution.

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Section: Discussionmentioning

confidence: 99%

Azimuthal Seismic Anisotropy of 70‐Ma Pacific‐Plate Upper Mantle

et al. 2019

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“…It necessitates a realignment of olivine anisotropic fabric over a lateral distance of~400-500 km, which requires large amounts of deformation (strains of~3-5 [Boneh and Skemer, 2014]). This is again in direct contrast to the plate-motion-parallel splitting we observe beneath our study region and infer for the subslab mantle beneath the Pampean flat slab.…”

Section: 1002/2017gl074312mentioning

confidence: 99%

Mantle flow through a tear in the Nazca slab inferred from shear wave splitting

Lynner

Anderson

Portner

et al. 2017

Geophysical Research Letters

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A tear in the subducting Nazca slab is located between the end of the Pampean flat slab and normally subducting oceanic lithosphere. Tomographic studies suggest mantle material flows through this opening. The best way to probe this hypothesis is through observations of seismic anisotropy, such as shear wave splitting. We examine patterns of shear wave splitting using data from two seismic deployments in Argentina that lay updip of the slab tear. We observe a simple pattern of plate‐motion‐parallel fast splitting directions, indicative of plate‐motion‐parallel mantle flow, beneath the majority of the stations. Our observed splitting contrasts previous observations to the north and south of the flat slab region. Since plate‐motion‐parallel splitting occurs only coincidentally with the slab tear, we propose mantle material flows through the opening resulting in Nazca plate‐motion‐parallel flow in both the subslab mantle and mantle wedge.

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“…Usually, steady state fabric is defined as the fabric having (i) a steady-state value of fabric strength, (ii) a steady-state value of symmetry elements (i.e., point, girdle, and random), and (iii) a steady-state alignment of the CPO with respect to the deformation geometry (Boneh and Skemer, 2014). In this study, we evaluate the evolution of fabric from the viewpoint of fabric strength and the alignment of CPO.…”

Section: Olivine Cpo Determined From ''In-situ'' Observationsmentioning

confidence: 99%

“…To evaluate the fabric strength quantitatively, the J-index (Bunge, 1982;Mainprice and Silver, 1993) and M-index (Skemer and Karato, 2008) have been used. Recently, the strain dependency on fabric evolution of olivine has been evaluated from microstructures of the quenched samples deformed at 0.3 GPa (Hansen et al, 2012(Hansen et al, , 2014 and 1 GPa (Boneh and Skemer, 2014). Hansen et al (2012Hansen et al ( , 2014 demonstrated that a steady-state fabric is not reached until a very large shear strain (c > 10) and fabric strength of olivine increases up to the J-index of 10-30 (M-index of 0.4-0.7).…”

Section: Introductionmentioning

confidence: 99%