Sound velocity of CaSiO3 perovskite suggests the presence of basaltic crust in the Earth’s lower mantle

Gréaux, Steeve; Irifune, Tetsuo; Higo, Yuji; Tange, Yoshinori; Arimoto, Takeshi; Liu, Zhaodong; Yamada, Akihiro

doi:10.1038/s41586-018-0816-5

Cited by 77 publications

(74 citation statements)

References 49 publications

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“…The calculated data used in this study are from previous ab initio molecular dynamic simulations 36 , while the Ca-perovskite data adopted in Thomson et al (2019) 54 were extrapolated from low pressure to the deep mantle conditions. Since velocities measured for Ca-perovskite 54,55 are considerably lower than computational predictions at the conditions of the uppermost lower mantle, the extrapolated data would be expectedly lower than theoretical calculations 36 under deep mantle conditions. It is still unknown what results in the discrepancies in sound velocities of Caperovskite between theoretical and experimental studies, and future research is needed to solve this problem.…”

Section: Discussionmentioning

confidence: 70%

“…It is still unknown what results in the discrepancies in sound velocities of Caperovskite between theoretical and experimental studies, and future research is needed to solve this problem. However, the uncertainties from extrapolation cannot be ignored because experimental measurements, especially high-temperature data, which also shows significant discrepancies 54,55 .…”

Section: Discussionmentioning

confidence: 99%

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Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities

Wang

Sun

et al. 2020

Nat Commun

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Seismic heterogeneities detected in the lower mantle were proposed to be related to subducted oceanic crust. However, the velocity and density of subducted oceanic crust at lowermantle conditions remain unknown. Here, we report ab initio results for the elastic properties of calcium ferrite-type phases and determine the velocities and density of oceanic crust along different mantle geotherms. We find that the subducted oceanic crust shows a large negative shear velocity anomaly at the phase boundary between stishovite and CaCl 2 -type silica, which is highly consistent with the feature of mid-mantle scatterers. After this phase transition in silica, subducted oceanic crust will be visible as high-velocity heterogeneities as imaged by seismic tomography. This study suggests that the presence of subducted oceanic crust could provide good explanations for some lower-mantle seismic heterogeneities with different length scales except large low shear velocity provinces (LLSVPs).

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Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities

Wang

Sun

et al. 2020

Nat Commun

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“…Seismic observations of deep reflectors in the depth range of 700 to 800 km have been interpreted variably as (a) the transformation of garnet to bridgmanite in garnet-rich crust (e.g., Lessing et al, 2014) consistent with mid-ocean ridge basalt (MORB) fractions in excess of 40% (Gréaux et al, 2019;Maguire et al, 2018), (b) the release of water from the downwelling slab through water-saturated ringwoodite breakdown (e.g., Schmandt et al, 2014), and (c) the release of water from the reabsorption of metallic iron at greater depths (e.g., Liu et al, 2016;Liu et al, 2018). However, each of these interpretations have some limitations.…”

Section: Introductionmentioning

confidence: 99%

Dehydration Melting Below the Undersaturated Transition Zone

Panero

Thomas

Myhill

et al. 2020

Geochem Geophys Geosyst

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A reflector 70–130 km below the base of the transition zone beneath Tibet is observed in receiver functions and underside seismic reflections, at depths consistent with the transition of garnet to bridgmanite. Contrast in water storage capacity between the minerals of the Earth's transition zone and lower mantle suggests the possibility for dehydration melting at the top of the lower mantle. First‐principles calculations combined with laboratory synthesis experiments constrain the mantle water capacity across the base of the transition zone and into the top of the lower mantle. We interpret the observed seismic signal as consistent with 3–4 vol % hydrous melt resulting from dehydration melting in the garnet to bridgmanite transition. Should seismic signals evident in downwelling region result from water contents representative of upper mantle water globally, this constrains the water stored in nominally anhydrous minerals in the mantle to <30% the mass of the surface oceans.

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“…Additional studies, including the large ratios between the shear-and compressible-wave speeds in the bodies of the LLSVPs (Ritsema & van Heijst, 2002) and the possible high-density anomalies at their bases (Ishii & Tromp, 1999;Lau et al, 2017), also support the chemical origin of the LLSVPs. To date, three possible chemical sources have been proposed for the LLSVPs: (1) the remnants of primordial dense materials that formed during the early stage of Earth's evolution (Labrosse et al, 2007;Zhang et al, 2016), (2) the products of core-mantle differentiation (Hayden & Watson, 2007;Kanda & Stevenson, 2006), and (3) the accumulation of eclogitic materials from recycled oceanic slabs (e.g., Christensen & Hofmann, 1994), which is supported by the existence of basaltic crust in the deep mantle (Gréaux et al, 2019). In this study, we focus on the third possibility from the perspective of geodynamic modeling.…”

Section: Introductionmentioning

confidence: 99%

The Continually Stable Subduction, Iron‐Spin Transition, and the Formation of LLSVPs From Subducted Oceanic Crust

Huang

Leng

2020

JGR Solid Earth

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Large low shear velocity provinces (LLSVPs) in the lower mantle beneath Africa and the Pacific Ocean have been widely accepted as compositionally distinct zones characterized by their large spatial scale, distinctive geometry (high topography and steep side boundaries), and long-term stability. One possible explanation for the chemical origin of the LLSVPs is that they formed from subducted oceanic crust. However, some previous geodynamic models suggest that it is difficult for a sufficient quantity of recycled crust to accumulate in the deep mantle and form chemical structures matching those of LLSVPs. Here we show that the continually stable subduction can significantly enhance the gathering of recycled oceanic crust above the core-mantle boundary. The resulting chemical structures in our model show high elevations and steep sides similar to those of the seismically observed LLSVPs when the effects of iron-spin transition in ferropericlase are incorporated. These LLSVP-like structures usually emerge 1-1.5 billion years (Gyr) after the model starts and remain recognizable at 3 Gyr. The total volume of these structures first increases to approximately double the current LLSVPs' volume and then gradually decreases over time. With a subduction pattern corresponding to extroversion supercontinent cycles, two antipodal chemical structures form similar to the current LLSVPs and survive longer than 1 Gyr.

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Sound velocity of CaSiO3 perovskite suggests the presence of basaltic crust in the Earth’s lower mantle

Cited by 77 publications

References 49 publications

Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities

Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities

Dehydration Melting Below the Undersaturated Transition Zone

The Continually Stable Subduction, Iron‐Spin Transition, and the Formation of LLSVPs From Subducted Oceanic Crust

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