Two-dimensional thermo-kinetic model for the olivine-spinel phase transition in subducting slabs

Däßler, Rolf; Yuen, D. A.; Karato, S.; Riedel, Michael R.

doi:10.1016/0031-9201(95)03103-0

Cited by 42 publications

(6 citation statements)

References 43 publications

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“…We estimate the rate constant of the olivine-wadsleyite phase transition (K) for two typical pressures of 13 and 16 GPa in the wadsleyite stability field assuming that preferential nucleation proceeds on GBs (including high-density dislocation walls) 25 . To estimate the rate of olivine-wadsleyite phase transition on grain boundaries under our experimental conditions, we adopt theoretical equations for the kinetics of polymorphic phase transitions on interfaces.…”

Section: Discussionmentioning

confidence: 99%

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In situ X-ray and acoustic observations of deep seismic faulting upon phase transitions in mantle olivine

Ohuchi

Higo

Tange

et al. 2022

Preprint

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Activity of deep earthquakes, which increases with depth from ~400 km to a peak at ~600 km and abruptly decreases to zero at 680 km, is enigmatic, because brittle failure is unlikely to occur under the corresponding pressures of 13−24 GPa. It has been suggested that pressure-induced phase transitions of olivine in subducted slabs are responsible for occurrence of the deep earthquakes, based on deformation experiments under pressure. However, most experiments were made using analogue materials of mantle olivine and at pressures below ~5 GPa, which are not applicable directly to the actual slabs. Here we report the results of deformation experiments combined with in situ X-ray observations and acoustic emission measurements on (Mg,Fe)2SiO4 olivine at 11−17 GPa and 860−1250 K, equivalent to the conditions of colder regions of the slabs subducted into the mantle transition region. We find that faulting occurs only at very limited temperatures of 1100−1160 K, accompanied by intense acoustic emissions from both inside and outside of the sample, immediately before the rupture. The formation of lenticular packets filled with nanocrystalline olivine and wadsleyite is confirmed in the recovered sample without faulting, indicating that the faulting is caused by adiabatic shear heating along the weak layer of the connected lenticular packets, where nanocrystalline olivine plays important roles. Our study suggests that the transformational faulting occurs on the isothermal surface of the metastable olivine wedge in subducted slabs, leading to deep earthquakes in limited regions and depth range.

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Section: Discussionmentioning

confidence: 99%

“…Reported values of ϕ = 6×10 -4 were used for nucleation of wadsleyite on grain 10 boundaries 25,26 . The values of ΔG * hom and ΔGr were calculated from the thermodynamic data of the olivine-wadsleyite transition 29 and the olivine-wadsleyite phase boundary 12 .…”

Section: Discussionmentioning

confidence: 99%

In situ X-ray and acoustic observations of deep seismic faulting upon phase transitions in mantle olivine

Ohuchi

Higo

Tange

et al. 2022

Preprint

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“…In both theories, as an earthquake ruptures in metastable olivine, small lenses of spinel are created in the fault gouge. Däßler et al (1996) recently showed theoretically that the metastable wedge can indeed extend to at least 600 km depth. Second, they found that the heat released in the metastable olivine to spinel phase change is three times greater than in the equilibrium phase change, resulting in localized heating in the slab of up to 150…”

Section: The Olivine To Spinel Phase Changementioning

confidence: 97%

“…• (Däßler et al, 1996) and [2] the small grain sizes further reduce the local slab strength (Riedel and Karato, 1997).…”

Section: Deep Earthquakes and Slab Rheologymentioning

confidence: 99%

NW Pacific slab rheology, the seismicity cutoff, and the olivine to spinel phase change

Castle

Creager

2014

Earth Planet Sp

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Along the Kamchatka-Kuril-Japan-Izu-Bonin-Mariana subduction zones, the old age of the subducting Pacific Plate and the rapid subduction rate together suggest that earthquakes should occur to the bottom of the transition zone. However, the seismicity cutoff varies in depth between 350 km and 650 km. Along these subduction zones, the largest deep-focus earthquakes invariably occur near the depth of the local seismicity cutoff regardless of its depth. The events near the seismicity cutoffs also have systematically different focal mechanisms than shallower events. Furthermore, data from S 660 P arrivals, residual sphere analysis, and tomographic studies all show that the slab dip consistently steepens to a near-vertical orientation at the seismicity cutoff. This change in slab dip indicates a strength loss in the slab. We hypothesize the following causal connection among all these observations: The cold temperatures in the slab kinetically hinder the olivine to spinel phase change and allow the olivine to persist metastably to depths well below its equilibrium pressure. When the phase transition occurs, it nucleates very finegrained spinel which acts as a lubricant, allowing the initiation of earthquake faulting at high confining pressures which further nucleates additional fine-grained spinel. The cold anomaly of the slab severely inhibits the growth of the nucleated spinel crystals. The presence of the fine-grained spinel crystals reduces the strength of the coldest part of the slab by several orders of magnitude, allowing high slab deformation rates. Additionally, the phase change, by increasing the density, provides a negative buoyancy force. Combined, these processes reduce the slab membrane strength and allow the slab to descend at a steeper dip.

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“…We estimate the nucleation rate of wadsleyite ( ) and the rate constant of the olivinewadsleyite phase transformation (k) for two typical pressures of 13 and 15.5 GPa in the wadsleyite stability field assuming that preferential nucleation proceeds on the crack surface 23 (see Supplementary Information). The results (Extended Data Fig.…”

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confidence: 99%

Deep seismic faulting triggered by nano-crystallization of wadsleyite from olivine

Ohuchi¹,

Higo²,

Tange³

et al. 2021

Preprint

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Activity of deep earthquakes, which increases with depth from ~400 km to a peak at ~600 km and abruptly decreases to zero at 680 km, is enigmatic, because brittle failure is unlikely to occur under the corresponding pressures of 13−24 GPa. It has been suggested that pressure-induced phase transformations of olivine in subducted slabs are responsible for occurrence of the deep earthquakes, based on deformation experiments under pressure. However, most experiments were made using analogue materials of mantle olivine and at pressures below ~5 GPa, which are not applicable directly to the actual slabs. Here we report the results of deformation experiments combined with in situ X-ray observations and acoustic emission measurements on (Mg,Fe)2SiO4 olivine at 11−17 GPa and 960−1250 K. We find that shear cracking followed by rapid formation of nano-crystalline wadsleyite on the crack surface is essential for the occurrence of faulting, which is observed only at temperatures around 1160 K. The faulting is accompanied by intense acoustic emissions and partial melting, which is likely to be induced by rapid sliding and adiabatic shear heating along the weak layer of nano-crystalline wadsleyite. In contrast, the olivine to ringwoodite transformation in (Mg,Fe)2SiO4 olivine would not cause such faulting because of the slow diffusion creep of ultrafine-grained ringwoodite. Our findings suggest the transformational faulting occurs on the surface of the metastable olivine wedge in subducted slabs, leading to deep earthquakes in the limited depth range.

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Two-dimensional thermo-kinetic model for the olivine-spinel phase transition in subducting slabs

Cited by 42 publications

References 43 publications

In situ X-ray and acoustic observations of deep seismic faulting upon phase transitions in mantle olivine

In situ X-ray and acoustic observations of deep seismic faulting upon phase transitions in mantle olivine

NW Pacific slab rheology, the seismicity cutoff, and the olivine to spinel phase change

Deep seismic faulting triggered by nano-crystallization of wadsleyite from olivine

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