Core formation, mantle differentiation and core-mantle interaction within Earth and the terrestrial planets

Trønnes, Reidar G.; Baron, M. A.; Eigenmann, Katarina R.; Guren, Marthe Grønlie; Heyn, Björn; Løken, Andreas; Mohn, Chris E.

doi:10.1016/j.tecto.2018.10.021

Cited by 78 publications

(98 citation statements)

References 251 publications

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“…Although tomographic images differ from one another, essentially all show extensive regions of low P and S wave speeds beneath Africa (Figures , , and ) and less extensive regions beneath the central Pacific Ocean (Figures , , and ). Dziewonski et al () and Trønnes et al () suggested that such a distribution of speeds, and therefore of mass, might be fixed to the Earth's rotation axis.…”

Section: Whole‐mantle Convection and The Lower Mantlementioning

confidence: 99%

“…Bridgmanite is much stronger than ferropericlase (e.g., Girard et al, ). Ballmer et al () exploited this difference to suggest that the LLSVPs consisted of “bridgmanite‐enriched ancient mantle structures.” The higher viscosity of the LLSVPs than surrounding material then contributes to long preservation of them (e.g., Ballmer et al, ; Davaille et al, ; Deschamps et al, ; Gonnermann et al, ; Heyn et al, ; Trønnes et al, ).…”

Section: A Chemically Stratified Lower Mantle Hot Spots Plumes Andmentioning

confidence: 99%

“…Also, for values of 0.275 < B < 0.35, Jaupart et al () derived a second relationship that gives a value of τ a few times smaller than that in (5), if the wavelength of the perturbation is taken to be 2 D . Obviously, from these simple arguments, as well as from more realistic models, a dense lowermost mantle could persist for durations of geologic eras (e.g., Tackley, ), if not the lifetime of the Earth (e.g., Ballmer et al, ; Deschamps et al, , ; Gonnermann et al, ; Heyn et al, ; Le Bars & Davaille, 2004b; Trønnes et al, ).…”

Section: A Chemically Stratified Lower Mantle Hot Spots Plumes Andmentioning

confidence: 99%

“…When rising hot, but otherwise chemically dense, material cools sufficiently, it should become denser than the surrounding material and sink back toward the core‐mantle boundary. A variety of arguments suggest that the period for such oscillatory convection could exceed 1 Ga, if not the age of the earth, so that the LLSVPs might have existed since the Earth formed (e.g., Ballmer et al, ; Deschamps et al, ; Gonnermann et al, ; Heyn et al, ; Trønnes et al, ). The period of oscillation depends on the buoyancy number, as given in (5) (e.g., Le Bars & Davaille, ), but constraints on chemical density anomalies in the lower mantle are too weak to allow tight bounds on their lifetimes.…”

Section: Summary and Possible Implicationsmentioning

confidence: 99%

“…and 6). Dziewonski et al (2010) and Trønnes et al (2019) suggested that such a distribution of speeds, and therefore of mass, might be fixed to the Earth's rotation axis.…”

Section: Whole-mantle Convection and The Lower Mantlementioning

confidence: 99%

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Lower Mantle Dynamics Perceived With 50 Years of Hindsight From Plate Tectonics

Molnár

2019

Geochem Geophys Geosyst

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Continually improving resolution of lower mantle structure and understanding of mantle dynamics suggest that, as in the plate-tectonics era, the upper and lower mantle may undergo little exchange. Although the phase transition at~660 km forms the sharpest seismologically mapped boundary within the mantle, another at 1,000 (±100) km might be more important for geodynamics. Contrasts in density and viscosity may limit penetration of upper and lower mantle through this boundary. Strong evidence, if still not definitive, calls for chemical heterogeneity of the lower mantle that manifests itself in a few energetic plumes rising from near the core mantle boundary and slowly evolving, larger piles or blobs of chemically distinct material. Those blobs or piles may deform little on billion-year timescales. Convection in the lower mantle might dictate some aspects of flow in the upper mantle, such as the positions of plumes and hot spots and the breakup of supercontinents, but its contribution to the speeds and directions that plates move might be negligible. The improved understanding of mantle convection has not overturned the simple, 50-year-old image that plates "drive themselves," with forces per unit length pushing them apart at spreading centers, excess mass in downgoing slabs pulling them down, and viscous drag on their bases (and tops at subduction zones) retarding movement. Remaining challenges include determining how convection in the lower mantle affects geologic history and using that history to constrain lower mantle dynamics.Plain Language Summary Fifty years ago, plate tectonics united many aspects of the surface geology of the Earth, but little connection to the lower mantle was seen. Today, most view plate tectonics as the relative movements of cold, top, stiff boundary layers of a convecting system that reaches to the core-mantle boundary and with aspects of the deep structure not foreseen decades ago. Large provinces in the deepest~1,000 km, in which P and S wave speeds are relatively low, not only seem to be chemically different from the neighboring mantle and from that at shallower depths, but their distribution also correlates with some aspects of the overlying surface geology, including the positions of major plumes rising from deep in the mantle and the positions of continents 100 to 200 Ma. These correlations imply a geodynamic connection between the lower mantle and the crust. Scaling laws derived from experiments in geophysical fluid mechanics suggest that the chemically distinct provinces may be relics from the earliest formation of the earth, but if not, they nevertheless have evolved slowly on the timescales of geologic eras. A concurrent emerging view of the lower mantle, however, also places increased emphasis on a boundary at~1,000 (±100) km depth, and this boundary might define a barrier to cold sinking slabs of lithosphere. A few isolated plumes of hot material that are also chemically different from most of the mantle penetrate this interface at 1,000 km, but it seems possible that this...

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Section: Whole‐mantle Convection and The Lower Mantlementioning

confidence: 99%

Section: A Chemically Stratified Lower Mantle Hot Spots Plumes Andmentioning

confidence: 99%

Section: A Chemically Stratified Lower Mantle Hot Spots Plumes Andmentioning

confidence: 99%

Section: Summary and Possible Implicationsmentioning

confidence: 99%

“…and 6). Dziewonski et al (2010) and Trønnes et al (2019) suggested that such a distribution of speeds, and therefore of mass, might be fixed to the Earth's rotation axis.…”

Section: Whole-mantle Convection and The Lower Mantlementioning

confidence: 99%

See 3 more Smart Citations

Lower Mantle Dynamics Perceived With 50 Years of Hindsight From Plate Tectonics

Molnár

2019

Geochem Geophys Geosyst

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Some Issues on Core‐Mantle Chemical Interactions: The Role of Core Formation Processes

Karato

2023

Core‐Mantle Co‐Evolution

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Connecting the Deep Earth and the Atmosphere

Torsvik

Svensen

Steinberger

et al. 2021

Mantle Convection and Surface Expressions

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Most hotspots, kimberlites, and large igneous provinces (LIPs) are sourced by plumes that rise from the margins of two large low shear-wave velocity provinces in the lowermost mantle. These thermochemical provinces have likely been quasi-stable for hundreds of millions, perhaps billions of years, and plume heads rise through the mantle in about 30 Myr or less. LIPs provide a direct link between the deep Earth and the atmosphere but environmental consequences depend on both their volumes and the composition of the crustal rocks they are emplaced through. LIP activity can alter the plate tectonic setting by creating and modifying plate boundaries and hence changing the paleogeography and its long-term forcing on climate.Extensive blankets of LIP-lava on the Earth's surface can also enhance silicate weathering and potentially lead to CO2 drawdown (cooling), but we find no clear relationship between LIPs and post-emplacement variation in atmospheric CO2 proxies on very long (>10 Myrs) timescales.Subduction is a key driving force behind plate tectonics but also a key driver for the long-term climate evolution through arc volcanism and degassing of CO2. Subduction fluxes derived from full-plate models provide a powerful way of estimating plate tectonic CO2 degassing (sourcing) and correlate well with zircon age frequency distributions through time. This suggest that continental arc activity may have played an important role in regulating long-term climate change (greenhouse vs. icehouse conditions) but only the Permo-Carboniferous icehouse (~330-275 Ma) show a clear correlation with the zircon record.

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Core formation, mantle differentiation and core-mantle interaction within Earth and the terrestrial planets

Cited by 78 publications

References 251 publications

Lower Mantle Dynamics Perceived With 50 Years of Hindsight From Plate Tectonics

Lower Mantle Dynamics Perceived With 50 Years of Hindsight From Plate Tectonics

Some Issues on Core‐Mantle Chemical Interactions: The Role of Core Formation Processes

Connecting the Deep Earth and the Atmosphere

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