Compositional and spectroscopic investigation of three ungrouped carbonaceous chondrites

1Mehmet Yesiltas,2Yoko Kebukawa,3Timothy D. Glotch,4Michael Zolensky,4Marc Fries,5Namik Aysal,5Fatma S. Tukel
Meteoritics & Planetary Science (in Press) Link to Article []
1Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli, 39100 Turkey
2Faculty of Engineering, Yokohama National University, 240-8501 Yokohama, Japan
3Department of Geosciences, Stony Brook University, Stony Brook, New York, 11790 USA
4Astromaterials Research and Exploration Science, Johnson Space Center, NASA, Houston, Texas, 77058 USA
5Department of Geological Engineering, Istanbul University-Cerrahpasa, Istanbul, 34320 Turkey
Published by arrangement with John Wiley & Sons

Ungrouped carbonaceous chondrites are not easily classified into one of the well-established groups due to compositional/petrological differences and geochemical anomalies. Type 2 ungrouped carbonaceous chondrites represent a very small fraction of all carbonaceous chondrites. They can potentially represent different aspects of asteroids and their regolith material. By conducting a multitechnique investigation, we show that Queen Alexandra Range (QUE) 99038 and Elephant Moraine (EET) 83226 do not resemble type 2 carbonaceous chondrites. QUE 99038 exhibits coarse-grained matrix, Fe-rich rims on olivines, and an apparent lack of tochilinite, suggesting that QUE 99038 has been metamorphosed. Its polyaromatic organic matter structures closely resemble oxidized CV3 chondrites. EET 83226 exhibits a clastic texture with high porosity and shows similarities to CO3 chondrites. It consists of numerous large chondrules with fine-grained rims that are often fragmented and discontinuous and set within matrix, suggesting a formation mechanism for the rims in a regolith environment. The kind of processes that can result in such chemical compositions as in QUE 99038 and EET 83226 is currently not fully known and clearly presents a conundrum. Tarda is a highly friable carbonaceous chondrite with close resemblance to Tagish Lake (ungrouped C2 chondrite). It comprises different types of chondrules (some with Fe-rich rims), framboid magnetite, sulfides, carbonates, and phyllosilicate- and carbon-rich matrix, and is consistent with being an ungrouped C2 chondrite.


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