¹Jens Barosch,^1,2Dominik C. Hezel,¹Lena Sawatzki,¹Lucia Halbauer,³Yves Marrocchi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13476]
¹Department of Geology and Mineralogy, University of Cologne, Zülpicher Str. 49b, 50674 Köln, Germany
²Department of Mineralogy, Natural History Museum, Cromwell Road, London, SW7 5BD UK
³CRPG, CNRS, Université de Lorraine, UMR 7358, Vandoeuvre‐lès‐Nancy, 54501 France
Published by arrangement with John Wiley & Sons

Mineralogically zoned chondrules are a common chondrule type in chondrites. They consist of olivine cores, surrounded by low‐Ca pyroxene rims. By serial sectioning porphyritic chondrules from carbonaceous, ordinary, and enstatite chondrites, we demonstrate that the 2‐D textural appearances of these chondrules largely depend on where they are cut. The same chondrule may appear as a porphyritic pyroxene (PP) chondrule when sectioned through the low‐Ca pyroxene rim, and as a porphyritic olivine‐pyroxene (POP) or porphyritic olivine (PO) chondrule when sectioned close or through its equator. Chondrules previously classified into PP/POP/PO chondrules might therefore not represent different types, but various sections through mineralogically zoned chondrules. Classifying chondrule textures into PP, POP, and PO has therefore no unequivocal genetic meaning, it is merely descriptive. Sectioning effects further introduce a systematic bias when determining mineralogically zoned chondrule fractions from 2‐D sections. We determined correction factors to estimate 3‐D mineralogically zoned chondrule fractions when these have been determined in 2‐D sections: 1.24 for carbonaceous chondrites, 1.29 for ordinary chondrites, and 1.62 for enstatite chondrites. Using these factors then shows that mineralogically zoned chondrules are the dominant chondrule type in chondrites with estimated 3‐D fractions of 92% in CC, 52% in OC, and 46% in EC.

¹Tomoya Obase,¹Daisuke Nakashima,¹Tomoki Nakamura,^2,3Keisuke Nagao
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13481]
¹Division of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University, Aoba, Sendai, Miyagi, 980‐8578 Japan
²Geochemical Research Center, Graduate School of Science, University of Tokyo, Hongo, Bunkyo, Tokyo, 113‐0033 Japan
³Division of Polar Earth‐System Sciences, Korea Polar Research Institute, 26 Songdomirae‐ro, Yeonsu‐gu, Incheon, 21990 Korea
Published by arrangement with John Wiley & Sons

We measured concentrations and isotopic ratios of noble gases in the Rumuruti (R) chondrite Mount Prestrud (PRE) 95410, a regolith breccia exhibiting dark/light structures. The meteorite contains solar and cosmogenic noble gases. Based on the solar and cosmogenic noble gas compositions, we calculated a heliocentric distance of its parent body, a cosmic‐ray exposure age on the parent body regolith (parent body exposure age), and a cosmic‐ray exposure age in interplanetary space (space exposure age) of the meteorite. Assuming a constant solar wind flux, the estimated heliocentric distance was smaller than 1.4 ± 0.3 au, suggesting inward migration from the asteroid belt regions where the parent body formed. The largest known Mars Trojan 5261 Eureka is a potential parent body of PRE 95410. Alternatively, it is possible that the solar wind flux at the time of the parent body exposure was higher by a factor of 2–3 compared to the lunar regolith exposure. In this case, the estimated heliocentric distance is within the asteroid belt region. The parent body exposure age is longer than 19.1 Ma. This result indicates frequent impact events on the parent body like that recorded for other solar‐gas‐rich meteorites. Assuming single‐stage exposure after an ejection event from the parent body, the space exposure age is 11.0 ± 1.1 Ma, which is close to the peak of ~10 Ma in the exposure age distribution for the solar‐gas‐free R chondrites.