Effect of Water on Subduction of Continental Materials to the Deep Earth

Ichikawa, Hiroki; Kawai, Kenji; Yamamoto, Shinji; Kameyama, Masanori

doi:10.1007/978-3-319-15627-9_9

Cited by 5 publications

(4 citation statements)

References 65 publications

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“…For instance, water lowers the melting temperatures of silicate rocks and could lead to melting in the deep Earth (Hirschmann, 2006). Water, present in trace quantities within nominally anhydrous minerals, affects the transport properties including rheology (e.g., Mei and Kohlstedt, 2000), viscosity (e.g., Ichikawa et al, 2015) and electrical conductivity (e.g., Wang et al, 2006). Water is transported into the deep Earth via subduction of hydrated lithosphere containing hydrous mineral phases (Kawamoto, 2006).…”

Section: Introductionmentioning

confidence: 99%

Elasticity of phase-Pi (Al3Si2O7(OH)3) – A hydrous aluminosilicate phase

Peng

Mookherjee

Hermann

et al. 2017

Physics of the Earth and Planetary Interiors

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Phase-Pi (Al 3 Si 2 O 7 (OH) 3) is an aluminosilicate hydrous mineral and is likely to be stable in hydrated sedimentary layers of subducting slabs. Phase-Pi is likely to be stable between the depths of 60 and 200 km and is likely to transport water into the Earth's interior. Here, we use first principles simulations based on density functional theory to explore the crystal structure at high-pressure, equation of state, and full elastic stiffness tensor as a function of pressure. We find that the pressure volume results could be described by a finite strain fit with ! " , # " , and # " ′ being 310.3 Å 3 , 133 GPa, and 3.6 respectively. At zero pressure, the full elastic stiffness tensor shows significant anisotropy with the diagonal principal components % && , % '' , and % ((being 235, 292, 266 GPa respectively, the diagonal shear %)) , % ** , and % ++ being 86, 92, and 87 GPa 2 respectively, and the off-diagonal stiffness % &

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Section: Introductionmentioning

confidence: 99%

Elasticity of phase-Pi (Al3Si2O7(OH)3) – A hydrous aluminosilicate phase

Peng

Mookherjee

Hermann

et al. 2017

Physics of the Earth and Planetary Interiors

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“…Since the region with u ( x , z ) < 0 exists in the granitic layer, a portion of the continental granitic materials goes upward and therefore a granitic layer with this thickness cannot be sustained. In summary, the viscosity of granitic materials mainly controls the maximum sustainable thickness of a granitic layer, as in the case of subduction channels [i.e., Ichikawa et al ., , ]. As will be discussed in more detail later in Figure , the change in magnitude of viscous drag in the granitic layer is attributed to the steep temperature gradient at around 2.5–3.0 GPa or around 80 km depth assumed by the D80 model of Syracuse et al .…”

Section: Resultsmentioning

confidence: 93%

“…The subduction of the Izu‐Bonin arc accounts for ~ 5 × 10 − 3 km 3 /yr (Figure ). This value is much smaller than the supply rate of continental materials due to the subduction channel, evaluated to be 2.2 km 3 /yr [ Ichikawa et al ., , ] but not negligibly small. In the present western Pacific, ~15 arcs are colliding [ Yamamoto et al ., ], which accounts for ~ 0.1 km 3 /yr in total.…”

Section: Discussionmentioning

confidence: 94%

“…In this mechanism, a ~2–3 km layer of subduction channels conveys granitic materials composed of sediments and eroded continental materials [ Cloos and Shreve , , ] from the surface to the mantle. In addition, ~2.2 km 3 /yr of granitic materials is thought to be conveyed into the deep mantle (below 270 km depth) through subduction channels according to numerical calculations [ Ichikawa et al ., , ]. The total volume of subducted granitic materials after the end of the Archaean is estimated to be approximately three fourths of the volume of the present continental crust.…”

Section: Introductionmentioning

confidence: 99%

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Estimate of subduction rate of island arcs to the deep mantle

et al. 2016

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Recent geological observations support the subduction of some oceanic arcs into the mantle. For example, the Izu‐Bonin arc is considered to be partially subducting underneath the island of Honshu, Japan, despite its lower density than that of surrounding mantle, after the vertical collision with Honshu at ~17 Ma. Seismological surveys have clarified the internal structure of the arc, which consists of the basaltic and boninitic upper crust, the felsic middle crust, the intermediate upper‐lower crust, and the mafic lower crust. This structure extends and moves northward toward Honshu. Among these components, part of the middle, the intermediate upper‐lower, and the lower crust is thought to be subducting. Here in order to estimate the subduction rate of granitic materials in oceanic arcs to the deep mantle, we have conducted numerical simulations of the subduction of arcs based on the finite element method and investigated the effect of arcs' sizes and shapes and slab temperature. The results show that the subduction rate heavily depends on the geometry of the arcs or temperature profiles of the subducting slabs. When the size of the arc or the temperature of the slab is smaller, the subduction rate grows larger owing to competition between upward buoyancy and downward viscous drag from slabs. The results also show that about 20% of the felsic crust materials in oceanic arcs that are comparable in size to the Izu‐Bonin arc can be subducted into the deep mantle when the temperature of the subducting slab is of the usual value.

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Elasticity of Continental Crust Around the Mantle Transition Zone

Kawai

Tsuchiya

2015

The Earth's Heterogeneous Mantle

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The fate and amount of granitic materials subducted into the deep mantle are still under debate. The density, elastic property, and phase stability of granitic materials in the mantle pressures are key to clarifying them. Here, we modeled highpressure properties of the granitic assemblage by using ab initio mineral physics data of grossular garnet, K-hollandite, jadeite, stishovite, and calcium ferrite (CF)-type phase. We find that the ongoing subducting granitic assemblage, such as sediments and average upper crust rocks, is much denser than pyrolite in the pressure range from 9 GPa (~270 km), at which coesite undergoes a phase transition to stishovite, to around 27 GPa (~740 km). Above this pressure, granitic material becomes less dense than a pyrolite. This indicates that the granitic assemblage becomes gravitationally stable at the base of the mantle transition zone (MTZ). Results suggest a possibility that the granitic materials could accumulate around the 740 km depth if carried into the depth deeper than 270 km and segregated at some depth. Comparison of the velocities between granitic and pyrolitic materials shows that granitic materials can produce substantial velocity anomalies in the MTZ and the uppermost lower mantle (LM). Seismic observations such as anomalously fast velocities, especially for the shear wave, around the 660-km discontinuity, the complexity of 660-km discontinuity, and the scatterers in the uppermost LM could be associated with the subducted granitic materials.

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Effect of Water on Subduction of Continental Materials to the Deep Earth

Cited by 5 publications

References 65 publications

Elasticity of phase-Pi (Al3Si2O7(OH)3) – A hydrous aluminosilicate phase

Elasticity of phase-Pi (Al3Si2O7(OH)3) – A hydrous aluminosilicate phase

Estimate of subduction rate of island arcs to the deep mantle

Elasticity of Continental Crust Around the Mantle Transition Zone

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