Isotopic and Chemical Evidence for Primitive Aqueous Alteration in the Tagish Lake Meteorite

Keisuke Sakuma1, Hiroshi Hidaka1, and Shigekazu Yoneda2

Astrophysical Journal 853, 92 Link to Article [DOI: 10.3847/1538-4357/aaa1e3]
1Department of Earth and Planetary Sciences, Nagoya University Nagoya 464-8601, Japan
2Department of Science and Engineering, National Museum of Nature and Science Tsukuba 305-0005, Japan

Aqueous alteration is one of the primitive activities that occurred on meteorite parent bodies in the early solar system. The Tagish Lake meteorite is known to show an intense parent body aqueous alteration signature. In this study, quantitative analyses of the alkaline elements and isotopic analyses of Sr and Ba from acid leachates of TL (C2-ungrouped) were performed to investigate effects of aqueous alteration. The main purpose of this study is to search for isotopic evidence of extinct 135Cs from the Ba isotopic analyses in the chemical separates from the Tagish Lake meteorite. Barium isotopic data from the leachates show variable 135Ba isotopic anomalies (ε = −2.6 ~ +3.6) which correlatewith 137Ba and 138Ba suggesting a heterogeneous distribution of s– and r-rich nucleosynthetic components in the early solar system. The 87Rb–87Sr and 135Cs–135Ba decay systems on TL in this study do not provide any chronological information. The disturbance of the TL chronometers is likely a reflection of the selective dissolution of Cs and Rb given the relatively higher mobility of Cs and Rb compared to Ba and Sr, respectively, during fluid mineral interactions.

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