Hydrolytic weakening of olivine at mantle pressure: Evidence of [100](010) slip system softening from single-crystal deformation experiments

Girard, Jennifer; Chen, Jiuhua; Raterron, Paul; Holyoke, C. W.

doi:10.1016/j.pepi.2012.10.009

Cited by 59 publications

(43 citation statements)

References 46 publications

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“…High hydrogen contents have also recently been observed in other continental regions worldwide that have been stable for billions of years (cratons) and therefore must be rheologically strong (for example, Kaapvaal 25 and Siberian 26 cratons). Furthermore, recent experiments on single olivine crystals have not observed a strong dependence of viscosity on hydrogen 12,27 and suggest that hydrogen-related weakening may be sensitive to grain size and unimportant at the large grain sizes of cratonic mantle. Further experimental work is required to test this.…”

Section: Lettersmentioning

confidence: 98%

Negligible effect of hydrogen content on plate strength in East Africa

Selway¹

2015

Nature Geosci

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Section: Lettersmentioning

confidence: 98%

Negligible effect of hydrogen content on plate strength in East Africa

Selway¹

2015

Nature Geosci

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“…These predictions however should be taken with caution since they are based on extrapolation of the moderate weakening (up to a factor 2) observed in deformation experiments on wet olivine single crystals and polycrystals at 300 MPa (Chopra and Paterson, 1984;Karato et al, 1986;Mei and Kohlstedt, 2000) to the higher water contents that might exist at higher pressure in the mantle. High-pressure deformation experiments on hydrated olivine single crystals (4740-11770 ppm wt H 2 O) show, however, less than a factor 2 decrease in strength relatively to dry conditions (Mackwell et al, 1985;Girard et al, 2013). Diffusion experiments under high-temperature and high-pressure conditions also suggest that incorporation of hydrogen has a weak effect on Si diffusion in olivine, which is considered to be the rate-controlling…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Heterogeneity and anisotropy in the lithospheric mantle

2015

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International audienceThe lithospheric mantle is intrinsically heterogeneous and anisotropic. These two properties govern the repartition of deformation, controlling intraplate strain localization and development of new plate boundaries. Geophysical and geological observations provide clues on the types, ranges, and characteristic length scales of heterogeneity and anisotropy in the lithospheric mantle. Seismic tomography points to variations in geothermal gradient and hence in rheological behavior at scales of hundreds of km. Seismic anisotropy data substantiate anisotropic physical properties consistent at scales of tens to hundreds of km. Receiver functions imply lateral and vertical heterogeneity at scales < 10 km, which might record gradients in composition or anisotropy. Observations on naturally deformed peridotites establish that compositional heterogeneity and Crystal Preferred Orientations (CPOs) are ubiquitous from the mm to the km scales. These data allow discussing the processes that produce/destroy heterogeneity and anisotropy and constraining the time scales over which they are active. This analysis highlights: (i) the role of deformation and reactive percolation of melts and fluids in producing compositional and structural heterogeneity and the feedbacks between these processes, (ii) the weak mechanical effect of mineralogical variations, and (iii) the low volumes of fine-grained microstructures and difficulty to preserve them. In contrast, olivine CPO and the resulting anisotropy of mechanical and thermal properties are only modified by deformation. Based on this analysis, we propose that strain localization at the plate scale is, at first order, controlled by large-scale variations in thermal structure and in CPO-induced anisotropy. In cold parts of the lithospheric mantle , grain size reduction may contribute to strain localization, but the low volume of fine-grained domains limits this effect

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“…Hydrous phases are likely the main sources of seismic shear anomalies because they often display lower strength than their dry counterparts and therefore form the strongest LPO in a rock (Chen et al, 1998;Girard et al, 2013;Kavner, 2003;Rosa et al, 2013a). Hydrous phases at depth might be most likely formed and/or preserved along fluid pathways, hence favoring the strain localization along shear bands that contain rheologically weak (hydrous) phases.…”

Section: Shear Wave Anisotropy Of Textured Shyb-bearing Peridotitesmentioning

confidence: 99%