High-spatial resolution U-Pb dating of phosphate minerals in Martian meteorite Allan Hills 84001
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概要
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Phosphate minerals, which are ubiquitous in terrestrial and extra-terrestrial rocks, are important carriers of trace elements, including U and Th, which provide chronological information because of their radioactive decay. Abundance and grain sizes of the phosphates are limited in extra-terrestrial materials. Therefore, high resolution and minimally or non-destructive analytical methods must be used for age determination. For this study, we conducted U-Pb dating using a NanoSIMS for three phosphate grains from an old Martian meteorite: ALH 84001. The 238U-206Pb and 207Pb-206Pb isochron ages were found to be 3850 ± 170 Ma and 4002 ± 52 Ma, respectively, suggesting a concordant signature at approx. 4.0 Ga. A total Pb/U isochron age of 3990 ± 160 Ma is consistent with a previous SHRIMP U-Pb age of 4018 ± 81 Ma (Terada et al., 2003). Moreover, heterogeneous distributions of U are observed in these grains, which might have been preserved since igneous crystallization of the phosphates because the diffusion of U in the mineral is considerably slow.
- 日本地球化学会の論文
著者
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Sugiura Naoji
Department Of Earth And Planetary Physics Faculty Of Science University Of Tokyo
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TAKAHATA NAOTO
Atmosphere and Ocean Research Institute, The University of Tokyo
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SANO YUJI
Atmosphere and Ocean Research Institute, The University of Tokyo
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KOIKE MIZUHO
Atmosphere and Ocean Research Institute, The University of Tokyo
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OTA YOSHIHIRO
Atmosphere and Ocean Research Institute, The University of Tokyo
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- High-spatial resolution U-Pb dating of phosphate minerals in Martian meteorite Allan Hills 84001