Shape and porosity of refractory inclusions in CV3 chondrites: A micro‐computed tomography (µCT) study

1,2Mingming Zhang,3Brett Clark,1,4Ashley J. King,1Sara S. Russell,2Yangting Lin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13635]
1Department of Earth Sciences, The Natural History Museum, Cromwell Road, SW7 5BD London, UK
2Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029 China
3Core Research Laboratories, The Natural History Museum, Cromwell Road, SW7 5BD London, UK
4School of Physical Sciences, The Open University, Walton Hall, MK7 6AA Milton Keynes, UK
Published by arrangement with John Wiley & Sons

Refractory calcium‐aluminum‐rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs) in chondritic meteorites are the earliest solids of our solar system, bearing the information of nebular condensation as well as accretion and asteroidal shock and metasomatism processes. While the compositions of refractory inclusions have been intensely studied for ~50 years, their physical properties such as shape and porosity are poorly constrained. Here, we present a microcomputed tomography (µCT) study on 16 refractory inclusions of condensate origin in five CV3 chondrites. We find that they are prolate or triaxial in shape with very rough morphologies. The CAIs have nodular textures and are thought to form by agglomerating individual nodules via collision‐induced bouncing and/or fragmentation, where the nodules were grown by gas–solid reactions during condensation. On the parent body, refractory inclusions from the CVR meteorite Leoville experienced intense shocks that led to the flattening of their shapes and lowering of their porosities. High‐temperature metasomatism in CVOxA meteorites and low‐temperature metasomatism in CVOxB meteorites do not seem to have large effects on the porosities of their refractory inclusions, which have similar ranges and pore‐size distributions. Instead, we infer that their pores are mostly inherited from the gas–solid condensation and subsequent agglomeration processes. The porosities of CAIs are higher than those of AOAs, which is mainly due to the high‐temperature sintering process of AOAs.

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