Description du projet
Comprendre l’évolution du manteau terrestre lors de sa solidification
Comment le manteau en fusion de la Terre s’est-il solidifié pour former une planète active sur le plan tectonique et géomagnétique? Le projet SEPtiM, financé par le CER, combinera la pétrologie expérimentale, la modélisation thermodynamique et les simulations géodynamiques de manière cohérente pour étudier la cristallisation du manteau en laboratoire. Il étudiera la séquence de cristallisation des silicates fondus concernés en laboratoire en utilisant un nouveau protocole dans une cellule à enclumes de diamant chauffée au laser, déterminera les relations de fusion et les diagrammes de phase, et les incorporera dans de nouveaux modèles géodynamiques. L’objectif global du projet consiste à simuler de manière réaliste l’évolution dynamique et thermochimique du manteau terrestre lors de sa solidification. Les résultats contribueront à comprendre les premières étapes de l’évolution de la Terre et des planètes en général.
Objectif
Earth’s mantle was extensively molten in its first 100 million years. Its solidification left a strong compositional and structural imprint on the mantle, still observable today in the geochemical and geophysical record. Isotopic variations in basalts and ancient crust reveal the existence of one or more mantle reservoirs that formed early in Earth’s history, and never fully remixed. Seismic tomography reveals large, chemically distinct, thermochemical structures in the lowermost mantle, anchored to the source of these anomalous basalts. These observations leave no doubt that the mantle still bears differentiated regions that preserve signatures of its solidification. However, their formation mechanisms and compositional evolution are still unknown. Unravelling those opens a new window in understanding the early stages of Earth and planetary evolution. The overarching question of this proposal: how did the primitive molten Earth solidify to form a tectonically and geomagnetically active planet? My goal is to address this question by investigating mantle crystallisation in the laboratory, by combining experimental petrology, thermodynamical modelling, and geodynamical simulations in a self-consistent fashion. I propose to assemble a multidisciplinary team to: (1) experimentally study the crystallisation sequence of relevant silicate melts in the laboratory under P-T conditions extending to those at of the depth of the core-mantle boundary, using a newly developed protocol in the laser-heated diamond anvil cell; (2) use these results to constrain a thermodynamical model of phase relations and compositions, and trace-element partitioning between solids and melts; (3) use DFT calculations to calculate the density and relative buoyancy of these solids and melts; (4) feed the thermodynamics and buoyancy as input to mushy two-phase 3D fluid dynamics simulations, to realistically simulate the dynamical and thermochemical evolution of Earth’s mantle as it solidified.
Champ scientifique
- humanitieshistory and archaeologyhistory
- natural sciencesphysical sciencesthermodynamics
- natural sciencesphysical sciencesclassical mechanicsfluid mechanicsfluid dynamics
- natural sciencesphysical sciencesastronomyplanetary sciencesplanets
- natural sciencesearth and related environmental sciencesgeologypetrology
Programme(s)
Thème(s)
Régime de financement
ERC-ADG - Advanced GrantInstitution d’accueil
75794 Paris
France