Formation of Horizontally Deflected Slabs in the Mantle Transition Zone Caused by Spinel‐to‐Post‐Spinel Phase Transition, Its Associated Grainsize Reduction Effects, and Trench Retreat

Mao, Wei; Zhong, Shijie

doi:10.1029/2021gl093679

Cited by 3 publications

(2 citation statements)

References 61 publications

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“…These types of models with realistic thermodynamic properties are more physically self‐consistent compared with previous models with either simplified thermodynamic properties or purely statistical models (Nakagawa et al., 2010). For the short‐term (tens of Myrs) subduction models, these new models show similar dynamic patterns as previous studies (Christensen, 1996; Mao & Zhong, 2021; Zhong & Gurnis, 1995). One of the largest differences is the complex density and seismic velocity pattern in the mantle transition zone (Figures S8–S10 in Supporting Information ), which previous models could not capture.…”

Section: Discussionsupporting

confidence: 83%

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On the Origin of Small‐Scale Seismic Scatters at 660‐km Depth

Mao

Gurnis

2022

Geochem Geophys Geosyst

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Seismic tomography models reveal broad long-wavelength structures associated with mantle convection. Both global and regional tomographic models resolve ubiquitous high velocity seismic anomalies in subduction zones, indicative of subduction of oceanic lithosphere into the deep mantle (e.g., Grand et al., 1997;. The seismic inversions show that diverse slab morphologies are imaged in the mantle transition zone (e.g.,

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Section: Discussionsupporting

confidence: 83%

“…Similar to previous computations of subduction zone dynamics, we varied trench retreat velocity to explore slab dynamics in the mantle transition zone. Our short‐term regional subduction models show similar dynamic evolution as in previous models with more simplified density (e.g., Christensen, 1996; Mao & Zhong, 2021; Zhong & Gurnis, 1995).…”

Section: Resultssupporting

confidence: 76%

On the Origin of Small‐Scale Seismic Scatters at 660‐km Depth

Mao

Gurnis

2022

Geochem Geophys Geosyst

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Constraints on the Fate of Delaminated Lithosphere in the Upper and Mid‐Mantle

Shi,

Morgan

2024

Geophysical Research Letters

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Delamination of lower continental lithosphere is known to have occurred under different tectonic settings. However, its fate in the mantle is poorly understood. By analyzing global seismic models, we find that most of likely lithosphere that delaminated during the Cenozoic and Mesozoic is preserved in the mantle transition zone, especially beneath North America and Africa. Numerical experiments indicates that delaminated lithosphere can remain stagnant in the mantle transition zone for tens of millions of years, followed by its potential sinking into the lower mantle or re‐rising to shallower depths depending on its density, the Clapeyron slope of the spinel‐to‐post‐spinel phase change and increase in mantle viscosity at ∼660–1,000 km depths. Re‐ascent occurs when delaminated lithosphere is reheated so that its effective density becomes lower than its surrounding ambient mantle after ∼100 Myr. Delaminated fragments can also potentially be mobilized by underlying global mantle flow to move horizontally away from plume regions.

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The role of mantle viscosity heterogeneities on the development of secondary plumes in the upper mantle

Li,

Wang,

Zhao

et al. 2023

Geophysical Journal International

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Summary Recent seismic observations have revealed diverse plume morphologies beneath hotspots that are characterized by multiple secondary plume branches with different sizes and temperatures. However, how the structures of these secondary plumes have developed and what controls the properties of these secondary plumes have not been well explored. Here, we performed 3-D numerical models to systematically investigate the effects of mantle viscosity structures and the strength of the 660-km phase change on the development of secondary plumes. We find that the characteristics of the secondary plumes, in terms of their numbers, excess temperatures, and sizes, are controlled by the Clapeyron slope of the 660-km phase change (γ660), the properties of the low viscosity layer beneath the mantle transition zone (viscosity reduction ratio, thickness, depth or phase change dependency of viscosity) and the presence of the weak asthenosphere. For γ660 between -2.0 and -3.0 MPa/K, the weak layer viscosity reduction ratio plays a first-order role in controlling secondary plume properties, i.e., a smaller viscosity reduction ratio results in more secondary plumes, higher plume excess temperature, and larger plume size. The thickness and viscosity dependencies of the weak layer have a secondary effect on secondary plume properties. However, a relatively small γ660 (e.g., -1.0 MPa/K) would result in a single secondary plume irrespective of the weak layer viscosity reduction ratio, the viscosity dependency, and whether with or without the weak asthenosphere. However, Our models also show that the presence of the weak asthenosphere has a prominent influence in increasing the number of secondary plumes but reducing the size of the plumes. Our results provide new insight into plume dynamics and suggest that the diverse plume structures observed in the upper mantle likely reflect different mantle viscosity structures beneath the hotspots.

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Formation of Horizontally Deflected Slabs in the Mantle Transition Zone Caused by Spinel‐to‐Post‐Spinel Phase Transition, Its Associated Grainsize Reduction Effects, and Trench Retreat

Cited by 3 publications

References 61 publications

On the Origin of Small‐Scale Seismic Scatters at 660‐km Depth

On the Origin of Small‐Scale Seismic Scatters at 660‐km Depth

Constraints on the Fate of Delaminated Lithosphere in the Upper and Mid‐Mantle

The role of mantle viscosity heterogeneities on the development of secondary plumes in the upper mantle

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