A new regime of slab-mantle coupling at the plate interface and its possible implications for the distribution of volcanoes

Morishige, Manabu

doi:10.1016/j.epsl.2015.07.011

Cited by 12 publications

(11 citation statements)

References 49 publications

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“…We observe that the weak serpentinite layer effectively decouples the movement between slab and mantle. This renders the fore‐arc mantle effectively stiff and leads to the formation of the cold corner in the mantle wedge as proposed in previous work [e.g., Honda , ; Wada et al , ; Morishige , ] (Figure a). Inside the serpentinite layer, the flow is similar to 1‐D channel flow except for the region around the downdip edge of the layer (Figure b).…”

Section: Resultsmentioning

confidence: 99%

“…The viscosity for the mantle wedge outside of the serpentinite layer is given by

η (T, \overset{ε}{true}) = {({}, \frac{1}{η_{diff} (T)} + \frac{1}{η_{disl} (T, \overset{ε}{true})} + \frac{1}{η_{\max}})}^{- 1}

where

η_{diff} (T) = A_{diff} \exp ({}, \frac{E_{diff}}{R (T + 273)})

η_{disl} (T, \overset{ε}{true}) = A_{disl} \exp ({}, \frac{E_{disl}}{nR (T + 273)}) {\overset{ε}{true}}^{(1 - n) / n}

\overset{ε}{true} = \sqrt{\frac{1}{2} {\overset{ε}{true}}_{ij} {\overset{ε}{true}}_{ij}} .

The viscosity in the serpentinite layer is assumed to be 2 × 10 18 Pa·s, because serpentinite is considered to be weak with limited temperature dependence [ Hilairet et al , ; Hirauchi et al , ]. This weak layer helps decouple the movement between slab and mantle and this leads to the formation of “cold corner” [ Honda , ; Wada et al , ; Morishige , ].…”

Section: Numerical Approachmentioning

confidence: 99%

“…The viscosity in the serpentinite layer is assumed to be 2 × 10 18 Pa⋅s, because serpentinite is considered to be weak with limited temperature dependence [Hilairet et al, 2007;Hirauchi et al, 2013]. This weak layer helps decouple the movement between slab and mantle and this leads to the formation of "cold corner" [Honda, 1985;Wada et al, 2008;Morishige, 2015].…”

Section: Matrix Velocity and Temperaturementioning

confidence: 99%

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Along‐arc variation in short‐term slow slip events caused by 3‐D fluid migration in subduction zones

Morishige

Keken

2017

JGR Solid Earth

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A strong correlation exists between the average slip rate by short‐term slow slip events (SSEs) and changes in the slab geometry in Cascadia and Nankai. The generation of short‐term SSEs is generally assumed to be related to the presence of fluids and we investigate the hypothesis that fluids released by metamorphic dehydration reactions migrate in 3‐D due to complex slab geometry. The associated along‐arc focusing of fluid flux is likely to cause higher average slip rate in certain patches. To test this hypothesis, we investigate how fluid migration is modified by along‐strike changes in slab geometry. We use a numerical model of two‐phase flow in subduction zones. In this model fluids migrate subparallel to the slab surface due to the anisotropic permeability inside a serpentinite layer just above the slab. In 3‐D, we find that fluids migrate in the maximum‐dip direction of the slab, rather than subparallel to the plate motion. As a result fluid paths concentrate with increasing porosity where the slab has a convex shape (and diverge with decreasing porosity where it has a concave shape). These results suggest that regions with a high average slip rate by short‐term SSEs in Cascadia and Nankai can be explained by 3‐D focusing of fluid migration. We predict a defocusing of fluids below the Kii Channel, Nankai, which may be the reason for the observed small slip by short‐term SSEs in this location.

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Section: Resultsmentioning

confidence: 99%

“…The viscosity for the mantle wedge outside of the serpentinite layer is given by

η (T, \overset{ε}{true}) = {({}, \frac{1}{η_{diff} (T)} + \frac{1}{η_{disl} (T, \overset{ε}{true})} + \frac{1}{η_{\max}})}^{- 1}

where

η_{diff} (T) = A_{diff} \exp ({}, \frac{E_{diff}}{R (T + 273)})

η_{disl} (T, \overset{ε}{true}) = A_{disl} \exp ({}, \frac{E_{disl}}{nR (T + 273)}) {\overset{ε}{true}}^{(1 - n) / n}

\overset{ε}{true} = \sqrt{\frac{1}{2} {\overset{ε}{true}}_{ij} {\overset{ε}{true}}_{ij}} .

Section: Numerical Approachmentioning

confidence: 99%

Section: Matrix Velocity and Temperaturementioning

confidence: 99%

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Along‐arc variation in short‐term slow slip events caused by 3‐D fluid migration in subduction zones

Morishige

Keken

2017

JGR Solid Earth

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“…Although regional fractures can cause segmentation of the volcanic arc front, there is no spatial correlation between the fracture zones and volcano distribution within an arc segment (Marsh, 1979; Pacey et al, 2013). Several studies, on the other hand, indicate that such regular spacing can be more readily conceived as a result of Rayleigh‐Taylor instability (RTI), where the characteristic wavelength of instabilities determines the spacing (Fedotov, 1975; Marsh & Carmichael, 1974; Morishige, 2015).…”

Section: Introductionmentioning

confidence: 99%

Cold Plumes Initiated by Rayleigh‐Taylor Instabilities in Subduction Zones, and Their Characteristic Volcanic Distributions: The Role of Slab Dip

et al. 2020

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Dehydration melting in subduction zones often produces cold plumes, initiated by Rayleigh‐Taylor instabilities in the buoyant partially molten zones lying above the dipping subducting slabs. We use scaled laboratory experiments to demonstrate how the slab dip (α) can control the evolution of such plumes. For α > 0°, Rayleigh‐Taylor instabilities evolve as two orthogonal waves, one trench perpendicular with wavelength λL and the other one trench parallel with wavelength λT (λT > λL). We show that two competing processes, (1) λL‐controlled updip advection of partially molten materials and (2) λT/λL interference, determine the modes of plume growth. The λT/λL interference gives rise to an areal distribution of plumes (Mode 1), whereas advection leads to a linear distribution of plumes (Mode 2) at the upper fringe of the partially molten layer. The λT wave instabilities do not grow when α exceeds a threshold value (α* = 30°). For α > α*, λL‐driven advection takes the control to produce exclusively Mode 2 plumes. We performed a series of 2‐D and 3‐D computational fluid dynamics simulations to test the criticality of slab dip in switching the Mode 1 to Mode 2 transition at α*. We discuss the effects of viscosity ratio (R) and the density contrast (Δρ) between the source layers and ambient mantle, source layer thickness (Ts), and slab velocity (Us) on the development of cold plumes. Finally, we discuss the areal versus linear distributions of volcanoes from natural subduction zones as possible examples of Mode 1 versus Mode 2 plume products.

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“…The convection results in alternating regions of mantle upwelling and downwelling, and volcanoes are more likely to form above the regions of hot mantle upwelling, forming volcanic clusters. Another proposed mechanism is the occurrence of isolated small mantle return flow in the mantle wedge 17 . This type of mantle flow has been simulated within a thin low-viscosity layer of 4–8 km thickness imposed at 50–70 km depths immediately above the subducting slab in a numerical subduction model, whereby the along-arc variation in the extent of the return flow is initiated by numerical noise in the thermal field 17 .…”

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confidence: 99%

Clustering of arc volcanoes caused by temperature perturbations in the back-arc mantle

Lee

Wada

2017

Nat Commun

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Clustering of arc volcanoes in subduction zones indicates along-arc variation in the physical condition of the underlying mantle where majority of arc magmas are generated. The sub-arc mantle is brought in from the back-arc largely by slab-driven mantle wedge flow. Dynamic processes in the back-arc, such as small-scale mantle convection, are likely to cause lateral variations in the back-arc mantle temperature. Here we use a simple three-dimensional numerical model to quantify the effects of back-arc temperature perturbations on the mantle wedge flow pattern and sub-arc mantle temperature. Our model calculations show that relatively small temperature perturbations in the back-arc result in vigorous inflow of hotter mantle and subdued inflow of colder mantle beneath the arc due to the temperature dependence of the mantle viscosity. This causes a three-dimensional mantle flow pattern that amplifies the along-arc variations in the sub-arc mantle temperature, providing a simple mechanism for volcano clustering.

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A new regime of slab-mantle coupling at the plate interface and its possible implications for the distribution of volcanoes

Cited by 12 publications

References 49 publications

Along‐arc variation in short‐term slow slip events caused by 3‐D fluid migration in subduction zones

Along‐arc variation in short‐term slow slip events caused by 3‐D fluid migration in subduction zones

Cold Plumes Initiated by Rayleigh‐Taylor Instabilities in Subduction Zones, and Their Characteristic Volcanic Distributions: The Role of Slab Dip

Clustering of arc volcanoes caused by temperature perturbations in the back-arc mantle

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