Homogenization of Earth’s mantle after magma ocean solidification
Notice bibliographique
Résumé
As Earth’s magma ocean solidified, chemical fractionation and physical separation of silicate melt and crystal produced chemical heterogeneity, potentially resulting in the compositional stratification of Earth’s deep mantle. A stratified deep mantle would have prevented advective flux of heat or material between the deep Earth (basal magma ocean (BMO) and core) and the shallow mantle. Therefore, the thermochemical evolution of the Earth hinges on the evolution of the stratified deep mantle. How does this region evolve, especially considering that it is likely underlaid by a radioactively heated BMO and a cooling core? To what extent and in what form would heterogeneity introduced by magma ocean differentiation be preserved in Earth’s mantle over time?We explored these questions through numerical experiments simulating the evolution of a compositionally stratified, initially solid layer underlaid by a volumetrically heated liquid layer. We model percolation as well as convection driven by density perturbations related to thermal expansion, composition (iron), and melt fraction, using pressure-dependent melting temperatures and density perturbations appropriate for Earth’s deep mantle. We explore a variety of heating rates, stratifications, and material properties.We find that the evolution of a stratified deep mantle may proceed in two regimes, depending on the competition between the timescales of (1) melt segregation and (2) mantle stirring driven by thermochemical convection.If stirring is efficient relative to melt segregation, bottom-heating will drive homogenization of a stratified region as heat added to deep material leads to density reduction through partial melting. In this regime, the timescale of homogenization is determined by the time it takes to deliver the energy necessary to reduce the density of the entire deep mantle to match that at the top of the stratified region. Density reduction can be achieved either by thermal expansion or melting; homogenization driven by melting-related density decrease will occur much more rapidly than homogenization driven by thermal expansion. The Earth’s solid mantle following deep mantle homogenization likely had multiple compositionally distinct layers (not including any BMO), which then would have proceeded to mix by entrainment.If melt segregation is efficient relative to stirring, bottom-heating will still produce partial melt, which will be dense due to the incompatibility of iron and will percolate to the BMO. This process drains incompatible components from the deep mantle to the BMO, with the depleted low-density residue rising in diapirs until the deep mantle is homogenized through depletion. In this case, the Earth is left with a mantle which is more uniform and more depleted than in the stirring-dominated regime, and a thicker BMO.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».