Formation of Thermochemical Heterogeneities by Core‐Mantle Interaction

Stein, Claudia; Hansen, Ulrich

doi:10.1029/2022jb025689

Cited by 4 publications

(7 citation statements)

References 106 publications

(247 reference statements)

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“…has also been benchmarked against several other open-source) mantle convection codes. All data supporting the findings of this study are available in the TRR 170 repository Stein and Hansen (2024).…”

Section: Discussionmentioning

confidence: 72%

“…The chemical boundaries are insulating at all sides so that here the dense material represents primordial material from early fractionation or differentiation processes. In this study, we neglect dense material being introduced into the solidified mantle from the core by core-mantle interaction (Stein & Hansen, 2023) or at the surface by impacts (Borgeat & Tackley, 2022).…”

Section: Model Setupmentioning

confidence: 99%

“…In this context, dense accumulations, that could be remnants of the magma ocean period (Ballmer, Lourenço, et al., 2017; Caracas et al., 2019; Labrosse et al., 2007), will also play an important role, as the material interacts with the convective flow. Additional sources for chemical heterogeneities could be dense material penetrating the mantle either by core‐mantle interaction (Stein & Hansen, 2023) or by impacts (e.g., Borgeat & Tackley, 2022). On the one hand, the dense material moves with the flow, forming dense piles beneath mantle plumes and being largely absent beneath subducted slabs (e.g., Lassak et al., 2007; McNamara & Zhong, 2005; Stein & Hansen, 2023; Steinberger & Torsvik, 2012), on the other hand, dense material has a restoring effect on rising plumes because the higher density counteracts with the thermal uplift and reduces the buoyancy (e.g., Dannberg & Sobolev, 2015).…”

Section: Introductionmentioning

confidence: 99%

“…Additional sources for chemical heterogeneities could be dense material penetrating the mantle either by core-mantle interaction (Stein & Hansen, 2023) or by impacts (e.g., Borgeat & Tackley, 2022). On the one hand, the dense material moves with the flow, forming dense piles beneath mantle plumes and being largely absent beneath subducted slabs (e.g., Lassak et al, 2007;McNamara & Zhong, 2005;Stein & Hansen, 2023;Steinberger & Torsvik, 2012), on the other hand, dense material has a restoring effect on rising plumes because the higher density counteracts with the thermal uplift and reduces the buoyancy (e.g., Dannberg & Sobolev, 2015). Consequently this affects plate motion, the surface expression of mantle convection.…”

Section: Introductionmentioning

confidence: 99%

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Onset of Plate Motion in the Presence of Chemical Heterogeneities in the Mantle and the Effect of Mantle Temperature

Stein,

Hansen

2024

JGR Solid Earth

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Chemical heterogeneities of various origins have been observed in the Earth's mantle. Their assumed higher density acts on the style of mantle convection and therefore, as tectonic plates form the highly viscous upper boundary layer of mantle convection, the onset of surface motion is also affected by chemical heterogeneities. We perform 2D basally heated thermochemical mantle convection models which initially include layers of dense material at different mantle depths. In comparison to purely thermal convection models, the onset of first plate motion is delayed. This delay is even more pronounced, the deeper the location of dense material, the larger its volume and the higher its density. Additionally, we varied the starting temperature of our models. In an initially hot mantle, a strong temperature‐dependent viscosity contrast between the mantle and cold surface leads to a cold, highly viscous plate (stagnant lid). For an initially cold mantle, rising plumes first need to transport basal heat upwards to create a sufficient viscosity contrast. Consequently, the formation and subsequent breaking of the stagnant lid is delayed. Considering a hotter mantle after Earth's magma ocean phase, we find that plate motion can occur within approximately the first 0.5 Gyr of solid‐state convection if no chemical structures are present or for dense material situated at the surface. Deep chemical heterogeneities delay the onset by at least one order of magnitude. Furthermore, the early surface motion will have been more erratic than todays stable plate motion, probably with a few single subduction events.

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Section: Discussionmentioning

confidence: 72%

Section: Model Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Onset of Plate Motion in the Presence of Chemical Heterogeneities in the Mantle and the Effect of Mantle Temperature

Stein,

Hansen

2024

JGR Solid Earth

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“…A low velocity layer at the CMB may originate from melting (Q. Williams & Garnero, 1996; Dannberg et al., 2021) or iron enrichment (Dobrosavljevic et al., 2019; Wicks et al., 2010). It could be the partially molten or solidified remnants of a basal magma ocean (Labrosse et al., 2007), the product of core‐mantle chemical exchange (e.g., Stein & Hansen, 2023), buoyant core‐derived solids (Fu et al., 2023; Mittal et al., 2020), or subducted material (e.g., Hansen et al., 2023). A partially molten lowermost mantle has been proposed for both the moon (Weber et al., 2011) and Mars (Samuel et al., 2021).…”

Section: Discussionmentioning

confidence: 99%

Evidence for a Kilometer‐Scale Seismically Slow Layer Atop the Core‐Mantle Boundary From Normal Modes

Russell,

Irving,

Jagt

et al. 2023

Geophysical Research Letters

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Geodynamic modeling and seismic studies have highlighted the possibility that a thin layer of low seismic velocities, potentially molten, may sit atop the core‐mantle boundary but has thus far eluded detection. In this study we employ normal modes, an independent data type to body waves, to assess the visibility of a seismically slow layer atop the core‐mantle boundary to normal mode center frequencies. Using forward modeling and a data set of 353 normal mode observations we find that some center frequencies are sensitive to one‐dimensional kilometer‐scale structure at the core‐mantle boundary. Furthermore, a global slow and dense layer 1–3 km thick is better‐fitting than no layer. The well‐fitting parameter space is broad with a wide range of possible seismic parameters, which precludes inferring a possible composition or phase. Our methodology cannot uniquely detect a layer in the Earth but one should be considered possible and accounted for in future studies.

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