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Variations in initial 26Al/27Al ratios among fluffy Type A Ca?Al-rich inclusions from reduced CV chondrites

Cited 4 time in wos
Cited 3 time in scopus
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Title
Variations in initial 26Al/27Al ratios among fluffy Type A Ca?Al-rich inclusions from reduced CV chondrites
Other Titles
CV 콘드라이트의 FTA CAI에 기록된 초기 26Al/27Al 조성비의 다양성
Authors
Noriyuki Kawasaki
Park, Changkun
Naoya Sakamoto
박선영
김현나
Minami Kuroda
Hisayoshi Yurimoto
Keywords
Al-Mg systematics; Ca-Al-rich inclusions; Early Solar System; SIMS
Issue Date
2019
Citation
Noriyuki Kawasaki, et al. 2019. "Variations in initial 26Al/27Al ratios among fluffy Type A Ca?Al-rich inclusions from reduced CV chondrites". EARTH AND PLANETARY SCIENCE LETTERS, 511(1): 25-35.
Abstract
Al-Mg mineral isochrons of three Ca-Al-rich inclusions (CAIs) that formed primarily by condensation, one fine-grained, spinel-rich inclusion and two fluffy Type A CAIs, from the reduced CV chondrites Efremovka and Vigarano were obtained by in situ Al-Mg isotope measurements using secondary ion mass spectrometry. The slope of the isochron obtained for the fine-grained, spinel-rich inclusion gives an initial 26Al/27Al value, (26Al/27Al)0, of (5.19 ± 0.17) × 10-5. This is essentially identical to the Solar System initial 26Al/27Al determined by whole-rock Al-Mg isochron studies for CAIs in CV chondrites. In contrast, the isochron slopes for the two fluffy Type A CAIs from their Al-Mg mineral isochrons, (4.703 ± 0.082) × 10-5 and (4.393 ± 0.084) × 10-5, are significantly lower than the Solar System initial value. The range of (26Al/27Al)0 values of the three CAIs, from (5.19 ± 0.17) to (4.393 ± 0.084) × 10-5, corresponds to a formation age spread of 0.17 ± 0.04 Myr. This formation age spread is similar to that of igneous CAIs from CV chondrites. The data suggest that condensation and melting of minerals occurred in the hot nebular gas contemporaneously for ~0.2 Myr at the very beginning of our Solar System, if 26Al was distributed homogeneously in the CAI forming region. Alternatively, the observed variations in (26Al/27Al)0 among fluffy Type A CAIs would also raise a possibility of heterogeneous distributions of 26Al in the forming region.
URI
http://repository.kopri.re.kr/handle/201206/9959
DOI
http://dx.doi.org/10.1016/j.epsl.2019.01.026
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