Elasticity of Phase H Under the Mantle Temperatures and Pressures: Implications for Discontinuities and Water Transport in the Mid‐Mantle

Song, Zijun; Wu, Zhongqing; Wang, Wenzhong; Hao, Shangqin; Sun, Daoyuan

doi:10.1029/2022jb024893

Cited by 3 publications

(3 citation statements)

References 122 publications

(212 reference statements)

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“…Our model shows that the two main dehydration depths at around 750 and 1,500 km where magmatism occurs, are consistent with seismic observations at subduction zones. Furthermore, the strongest mid‐lower mantle scatters are detected within a narrow range between 1,500 and 1,600 km beneath central America, Tonga, and Mariana (Kaneshima, 2016 and reference therein), coincidently corresponding to the dehydration depth of phase H in the MSH system (Nishi et al., 2018; Ohtani, 2021; Ohtani et al., 2014; Song et al., 2022; Walter et al., 2015). Partial melt could thus explain the low seismic velocity and strong seismic attenuation at ∼1,500 km if the water storage capacity of the oceanic crust is relatively low or the crust cannot absorb all the water released by the slab (Figure 10).…”

Section: Discussionmentioning

confidence: 99%

On the Dynamics of Water Transportation and Magmatism in the Mid‐Mantle

Yang

Faccenda

2023

JGR Solid Earth

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The distribution of water within the Earth's mantle has significant implications for the Earth's dynamics and evolution. Recent mineral physics experiments indicate that dense hydrous magnesium silicates can contain large amounts of water stable up to 60 GPa or even beyond along slab geotherms. Here we perform petrological‐thermomechanical numerical simulations of water transportation by deep slab subduction and related magmatism in the mid‐mantle. Key parameters including those defining the slab thermal parameter and the water storage capacity in the oceanic lithosphere and surrounding mantle are explored. The results show two major dehydration events of ultramafic rocks at around 150 and 750 km by dehydration of serpentine at 600°C and superhydrous phase B in the entrained wet upper mantle, respectively. Large amounts of water, ∼1.5 wt% at least locally, are carried down to the mantle transition zone and lower mantle. We estimate an upper limit of slab water flux into the mid‐mantle of 0.1–0.28 × 1012 kg/yr, which is ∼13%–37% of the input water from the serpentinized mantle. Moreover, a substantial fraction of the water released by the slab is absorbed by the entrained mantle and overlying mid‐mantle portions, such that ∼30%–70% of the water injected at the trench could be delivered to the lower mantle. The deepest magmatism is observed at ∼1,500 km in case of phase H breakdown (MgO‐SiO2‐H2O system), coinciding with the depth of strong seismic attenuation. Overall, these simulations suggest that up to 0.2 ocean mass per billion years could be transported down to the mid‐mantle and beyond.

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Section: Discussionmentioning

confidence: 99%

On the Dynamics of Water Transportation and Magmatism in the Mid‐Mantle

Yang

Faccenda

2023

JGR Solid Earth

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“…This method has been applied successfully to many minerals (Deng et al., 2022, 2023; Duan et al., 2019; Hao et al., 2019; Z. J. Song et al., 2022; Wang et al., 2020; Wu & Wang, 2016; Zhao et al., 2022). Additionally, the phase boundary was determined by comparing the Gibbs free energy of the reactant and the product, which is directly deduced from F from G ( P , T ) = F ( V , T ) + P ( V , T ) V .…”

Section: Methodsmentioning

confidence: 99%

Elasticity of Anhydrous Phase B Under Mantle Conditions: Implications for the Deep X‐Discontinuity in the Subduction Zones

Song,

Wang,

2023

Geochem Geophys Geosyst

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Anhydrous phase B (anh‐B) is a dense magnesium silicate with the composition Mg14Si5O24 and space group Pmcb. In magnesium‐rich environments, forsterite reacts with periclase to form anh‐B, and the formation of anh‐B was proposed as a plausible mechanism for the origin of the X‐discontinuity. However, the elastic properties of anh‐B, which are critical for evaluating the seismic features associated with its formation, have not been determined. In this study, we investigated the elasticity of anh‐B at high pressure and temperature via first‐principles calculations. Combining with the elasticity of other minerals, we determined the contrasts caused by the formation of anh‐B: ∼3%, ∼7%, and ∼10% jumps for density, VP, and VS, respectively. The 2%–8% impedance contrasts of the X‐discontinuity can be explained by the formation of 15–60 vol% anh‐B, which requires 3–12 vol% MgO as a reactant.

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“…Additionally, the elasticity of dolomite has also been investigated by atomistic simulations (Titiloye et al., 1998) and first‐principles calculations (Bakri & Zaoui, 2011; Marcondes et al., 2016) at static conditions. Pressure and temperature generally have a great influence on the elasticity of minerals (Deng et al., 2022; Song et al., 2022; Zhao et al., 2022) and the P‐T conditions corresponding to the MLD in cratonic regions are ∼2–5 GPa and ∼600–1200°C (Chen, 2017; Karato et al., 2015). In addition, the cation disordering of dolomite is initiated at 3 GPa and ∼950°C (Hammouda et al., 2011).…”

Section: Introductionmentioning

confidence: 99%

Is There a Carbonated Mid‐Lithosphere Discontinuity in Cratons?

Zhao,

Deng,

Chen

et al. 2024

JGR Solid Earth

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The mid‐lithosphere discontinuity (MLD), identified by a sharp velocity drop at ∼70–100 km depths within the cratonic lithosphere is key to comprehending the chemical composition and thermal structure of the cratonic lithosphere. The MLD is widely accepted to be caused by composition anomalies, such as hydrous minerals, which show low velocities and high electrical conductivities. However, noticeable high‐electrical conductivity anomalies have not been detected in the most cratonic lithosphere. Dolomite has an electrical conductivity similar to olivine and can be originated by carbonatitic melts trapped at ∼80–140 km depths. Here we investigated the elasticity of dolomite under mantle conditions using ab initio calculations and found dolomite exhibits significantly lower velocities than the primary minerals in the lithospheric mantle. Therefore, the dolomite enrichment might provide a good explanation for the observed velocity drop of the MLD in cratonic regions where no high‐conductivity anomaly has been detected, such as the northern Slave craton.

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Elasticity of Phase H Under the Mantle Temperatures and Pressures: Implications for Discontinuities and Water Transport in the Mid‐Mantle

Abstract: Water is key to the evolution of the Earth's mantle because it could significantly affect the physical properties of the rocks in the Earth's interior, including viscosity, melting temperature, electrical conductivity, diffusion rate, and phase boundary (e.g.

Cited by 3 publications

References 122 publications

On the Dynamics of Water Transportation and Magmatism in the Mid‐Mantle

On the Dynamics of Water Transportation and Magmatism in the Mid‐Mantle

Elasticity of Anhydrous Phase B Under Mantle Conditions: Implications for the Deep X‐Discontinuity in the Subduction Zones

Is There a Carbonated Mid‐Lithosphere Discontinuity in Cratons?

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