Formation of chondrules and matrix in Kakangari chondrites

1Jens Barosch,2,3,4Denton S.Ebel,1,5Dominik C.Hezel,2Samuel Alpert,6Herbert Palme
Earth and Planetary Science Letters 542, 115286 Link to Article [https://doi.org/10.1016/j.epsl.2020.116286]
1University of Cologne, Department of Geology and Mineralogy, Zülpicher Str. 49b, 50674 Köln, Germany
2American Museum of Natural History, Department of Earth and Planetary Sciences, NY 10024, New York, USA
3Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
4Graduate School and Graduate Center of the City University of New York, NY, USA
5Natural History Museum, Department of Mineralogy, Cromwell Road, SW7 5BD, London, UK
6Forschungsinstitut und Naturmuseum Senckenberg, Senckenberganlage 25, D-60325, Frankfurt am Main, Germany
Copyright Elsevier

The study of chondritic meteorites and their components allows us to understand processes and conditions in the protoplanetary disk. Chondrites with high and about equal proportions of chondrules and matrix are ideal candidates to not only study the formation conditions of chondrules, but also the relationship between these two major components. An important question is whether these formed in the same or in separate reservoirs in the protoplanetary disk. So far, such studies have been mainly restricted to carbonaceous chondrites. We here expand these studies to the K (Kakangari-like) chondrite grouplet. These have various distinctive properties, but the abundance of major components – chondrules and matrix – is similar to other primitive meteorites. We obtained a comprehensive petrographic and chemical dataset of Kakangari and Lewis Cliff 87232 chondrules and matrix. Chondrules in Kakangari show a large compositional scatter, supporting material addition to chondrules during their formation. Contrary to almost all other chondrite groups, the majority of Kakangari chondrules are not mineralogically zoned. However, Kakangari chondrules were likely initially zoned, but then lost this zonation during chondrule remelting and fragmentation. Average compositions of bulk chondrules, matrix and bulk Kakangari are identical and approximately solar for Mg/Si. This might indicate the formation of chondrules and matrix from a common reservoir and would agree with findings from carbonaceous and Rumuruti chondrites: chondrules and matrix in most chondrite groups were not transported through the protoplanetary disk and then mixed together. Rather, these major components are genetically related to each other and formed in the same reservoir.

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