Reproducing iron-rich phase textures in primitive achondrites: overcoming surface tension in solids

• DOI: 10.7185/gold2023.17908
• Publication Date: 2023-12-11T11:28:26Z
• Authors: Adrien Néri; Edith Kubik; Gregor Golabek; Audrey Bouvier; Nicolas Walte
• Keywords: Achondrite

Primitive achondrites are partially differentiated meteorites originating from parent bodies that accreted around 1.3 Myr after CAIs [1].Despite a limited heating potential (up to ≈ 1200 °C and 25 vol% of melting for lodranites [2]), the silicate fraction these specimens shows high degree equilibration, based on homogeneous phase compositions equilibrated textural features.However, textures opaque phases in acapulcoites do not reflect an equilibrium defined by interfacial energies.At peak temperatures, metallic most likely featured Fe-Ni residue sulfur-rich melt.In this state, minimization energies dictates residual grains surrounded S-rich melt.Instead, kamacite-taenite troilite equally contacting spatially sorted within sections primitive achondrites.To understand origin textures, analogue system was designed using olivine mixture gold represent low-and high-surface tension melt residue, respectively.Samples were enclosed graphite capsules compressed 2.5 GPa 500 tons Walker-type multianvil press at BGI.From our recovered samples, it appears long equilibration solid initial temperature is necessary reproduce spatial sorting phases.The cooling history body rather than high-temperature equilibration.During slow planetesimal, viscosity makes inefficient.Although energetically favorable, graingrowth occurs over reasonable timescales controls smallscale reorganization topological rearrangement adjacent grain-boundaries.Hence, sub-solidus grain growth results phases.Since such features indicate cooling, they can be used place constraints onto thermal evolution planetesimals possibility timing impacts.