Formation of large low shear velocity provinces through the decomposition of oxidized mantle

Wang, Wenzhong; Liu, Jiachao; Zhu, Feng; Li, Mingming; Dorfman, Susannah M.; Li, Jie; Wu, Zhongqing

doi:10.1038/s41467-021-22185-1

Cited by 19 publications

(17 citation statements)

References 76 publications

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“…The Fe 2 O 3 ‐rich samples in this study and some other studies (e.g., Andrault & Bolfan‐Casanova, 2001; Liu et al., 2018; Wang et al., 2021) show much higher Fe 3+ contents in bridgmanite (up to 1.0 pfu) than the current MgO‐rich bridgmanite samples. However, these high Fe 3+ ‐content bridgmanite samples did not coexist with ferropericlase (bridgmanite + MgFe 2 O 4 ‐phase in Fe 2 O 3 ‐rich samples in this study and only bridgmanite in Andrault & Bolfan‐Casanova, 2001, Liu et al., 2018, and Wang et al., 2021). When bridgmanite coexists with ferropericlase, the Fe 3+ content in bridgmanite will be limited because of the formation of the MgFe 2 O 4 ‐phase from FeFeO 3 and MgO (Andrault & Bolfan‐Casanova, 2001).…”

Section: Discussionsupporting

confidence: 58%

“…(2018) and Wang et al. (2021). This is understandable because the molar volume of hematite (30.5 cm 3 /mol) is slightly larger than the FeFeO 3 component in bridgmanite (29.55 cm 3 /mol, Huang, Boffa‐Ballaran, McCammon, Miyajima, & Frost, 2021).…”

Section: Discussionmentioning

confidence: 97%

“…When bridgmanite does not coexist with MgO, the Fe 3+ content in bridgmanite depends on the starting material. If the bulk Fe 3+ content in the starting material is high, the Fe 3+ content in bridgmanite can accordingly be high based on the phase relations in Figure 1, for example, Fe 3+ can reach 1.0 pfu as shown in Liu et al (2018) and Wang et al (2021). This is understandable because the molar volume of hematite (30.5 cm 3 /mol) is slightly larger than the FeFeO 3 component in bridgmanite (29.55 cm 3 /mol, Huang, Boffa-Ballaran, .…”

Section: Fe 3+ Content In Bridgmanitementioning

confidence: 99%

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Pressure Destabilizes Oxygen Vacancies in Bridgmanite

et al. 2021

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Bridgmanite may contain a large proportion of ferric iron in its crystal structure in the forms of FeFeO3 and MgFeO2.5 components. We investigated the pressure dependence of FeFeO3 and MgFeO2.5 contents in bridgmanite coexisting with MgFe2O4‐phase and with or without ferropericlase in the MgO‐SiO2‐Fe2O3 ternary system at 2,300 K, 33 and 40 GPa. Together with the experiments at 27 GPa reported in Fei et al. (2020, https://doi.org/10.1029/2019GL086296), our results show that the FeFeO3 and MgFeO2.5 contents in bridgmanite decrease from 7.6 to 5.3 mol % and from 2 to 3 mol % to nearly zero, respectively, with increasing pressure from 27 to 40 GPa. Accordingly, the total Fe3+ decreases from 0.18 to 0.11 pfu. The formation of oxygen vacancies (MgFeO2.5 component) in bridgmanite is therefore dramatically suppressed by pressure. Oxygen vacancies can be produced by ferric iron in Fe3+‐rich bridgmanite under the topmost lower mantle conditions, but the concentration should decrease rapidly with increasing pressure. The variation of oxygen‐vacancy content with depth may potentially affect the physical properties of bridgmanite and thus affect mantle dynamics.

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Section: Discussionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 97%

Section: Fe 3+ Content In Bridgmanitementioning

confidence: 99%

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Pressure Destabilizes Oxygen Vacancies in Bridgmanite

et al. 2021

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“…For some models, a third layer is added just above the CMB (150, 200, or 250 km thick) for which we impose the same physical properties as for basalt. This intrinsically dense layer is thought to represent an iron-enriched material, e.g., originat-ing from the last cumulates from a crystallizing basal magma ocean (e.g., Wang et al, 2021) or from ancient crust that settled at the CMB (Elkins-Tanton et al, 2003).…”

Section: Initial Set-up Of the Modelsmentioning

confidence: 99%

Coupled dynamics and evolution of primordial and recycled heterogeneity in Earth’s lower mantle

Gülcher¹,

Ballmer²,

Tackley³

2022

Preprint

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The nature of compositional heterogeneity in Earth’s lower mantle remains a long-standing puzzle that can inform about the long-term thermochemical evolution and dynamics of our planet. Here, we use global-scale 2D models of thermo- chemical mantle convection to investigate the coupled evolution and mixing of (intrinsically-dense) recycled and (intrinsically- strong) primordial heterogeneity in the mantle. We explore the effects of ancient compositional layering of the mantle, as motivated by magma-ocean solidification studies, and of the physical parameters of primordial material. Depending on these physical parameters, our models predict various regimes of mantle evolution and heterogeneity preservation over 4.5 Gyrs. Over a wide parameter range, primordial and recycled heterogeneity are predicted to co-exist with each other in the lower mantle of Earth-like planets. Primordial material usually survives as mid-to-large scale blobs (or streaks) in the mid-mantle, around 1000-2000 km depth, and this preservation is largely independent on the initial primordial-material volume. In turn, recycled oceanic crust (ROC) persists as large piles at the base of the mantle and as small streaks everywhere else. In models with an additional dense FeO-rich layer initially present at the base of the mantle, the ancient dense material partially survives at the top of ROC piles, causing the piles to be compositionally stratified. Moreover, the addition of such an ancient FeO-rich basal layer significantly aids the preservation of the viscous domains in the mid-mantle. Finally, we find that primordial blobs are commonly directly underlain by thick ROC piles, and aid their longevity and stability. Based on our results, we propose an integrated style of mantle heterogeneity for the Earth, involving the preservation of primordial domains along with recycled piles. This style has important implications for early Earth evolution, and has the potential of reconciling geophysical and geochemical discrepancies on present-day lower-mantle heterogeneity.

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“… 1 , 2 , 3 These heterogeneities are distinguished through reduced seismic velocities and seismic wave reflections and can be generated by the presence of melt or fluid, 3 or by thermal and chemical variations in the mantle. 4 , 5 In this context, diamonds provide key information because some of them contain inclusions that were entrapped in the TZ or LM, 6 , 7 , 8 , 9 , 10 , 11 and, hence, are part of the global deep-carbon cycle. Generally, diamond formation is not bound to subduction.…”

Section: Introductionmentioning

confidence: 99%

Coupled deep-mantle carbon-water cycle: Evidence from lower-mantle diamonds

et al. 2021

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A novel approach was developed to assess the pressure-temperature conditions of entrapment of inclusions in diamonds -The viscoelastic relaxation of diamond has a significant effect on the evolution of pressure and temperature -Ice-VII-bearing diamonds have formed in wet, cool environments at depths down to 800 km -The coupled recycling of water and carbon is present in the deep mantle ll www.cell.com/the-innovation

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Formation of large low shear velocity provinces through the decomposition of oxidized mantle

Cited by 19 publications

References 76 publications

Pressure Destabilizes Oxygen Vacancies in Bridgmanite

Pressure Destabilizes Oxygen Vacancies in Bridgmanite

Coupled dynamics and evolution of primordial and recycled heterogeneity in Earth’s lower mantle

Coupled deep-mantle carbon-water cycle: Evidence from lower-mantle diamonds

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