The formation of primitive meteorites and their modification in their primitive parent bodies: a matter of fluid mechanics? - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2020

The formation of primitive meteorites and their modification in their primitive parent bodies: a matter of fluid mechanics?

Clément Ganino

Résumé

Chondrites are considered as the most primitive meteorites and represent a tangible record of astrophysical and geologic processes that occurred during the first 5-10 Ma of solar system history within the protoplanetary disk that surrounded the proto-Sun after its birth 4,567 Ga ago. They are presently our best witness-samples to understand the formation and evolution of the early solar system. They consist in lithified samples of materials that originate from small asteroid bodies from within the main asteroid belt ~ 3 AU (astronomical units) from the Sun or possibly further out from the Sun. Chondrules are one of the major components of primitive meteorites. Their sphericity indicates they formed as molten fragments or droplets but conditions and mechanisms of chondrule formation remain unknown. A possible scenario is their formation during hypervelocity impacts and ejections. I will show the result from an experiment that reproduces analogous of iron metal -rich chondrules by impact between a glassy silicate projectile and a metallic steel target. Silicate ejecta share several similarities with chondrules. The silicate ejecta formed in the ejecta plume contains numerous small size spherical iron metal beads as also observed in numerous natural chondrules. We attribute the morphology of ejecta and their small metal beads to the blast dynamics: for a same velocity and surface tension, fragments of silicate liquid are stable when iron liquid fragments of similar size are separated into smaller droplets. Once chondrules and the various other chondrite components (refractory inclusions, matrices) had formed, they accreted into meteorite parent bodies within the disk. If few chondrites still preserve a pristine record of this early solar nebular evolution, the great majority has been affected by secondary processes occurring prior or after their accretion in their asteroid parent bodies. These secondary thermal processes, involved fluid/solid interaction (Darcy percolation) and include gas-solid interactions, aqueous alteration, metasomatism and metamorphism. They have all acted to modify the very early record of these chondrites to different degrees from a chemical/mineralogical point of view and by changing their physical properties (i.e. pore-filling (precipitation) versus leaching and their consequences on the porosity). Here I will show that the petrological record of chondrite and discuss the future challenges to understand the modification of pristine meteorites by reacting complex fluids and build a comprehensive history of the early evolution of the first planetesimals.
Fichier non déposé

Dates et versions

hal-03044036 , version 1 (07-12-2020)

Identifiants

  • HAL Id : hal-03044036 , version 1

Citer

Clément Ganino. The formation of primitive meteorites and their modification in their primitive parent bodies: a matter of fluid mechanics?. Fluids and Complexity - Nice 2020-12-7, Fondation Doeblin - Céline Cohen, Rudy Valette, Xavier Noblin, Dec 2020, Nice, France. ⟨hal-03044036⟩
26 Consultations
0 Téléchargements

Partager

Gmail Facebook X LinkedIn More