TY - JOUR
T1 - Contemporaneous formation of chondrules in distinct oxygen isotope reservoirs
AU - Ushikubo, Takayuki
AU - Nakashima, Daisuke
AU - Kimura, Makoto
AU - Tenner, Travis J.
AU - Kita, Noriko T.
N1 - Funding Information:
The authors thank Glenn J. MacPherson and Linda Welzenbach, Smithsonian Institute, for the use of Acfer 094 thin section. Harold C. Connolly J.r, Hisayoshi Yurimoto, and Kazuhide Nagashima provided helpful comments that improved this manuscript. This work is supported by NASA (NNX07AI46G, NNX11AG62G, NK) and a Grant-in-aids of Ministry of Education, Science, and Culture (No. 22540488, MK). WiscSIMS is partly supported by NSF (EAR03-19230, EAR07-44079).
PY - 2013/5/5
Y1 - 2013/5/5
N2 - We investigated the 26Al-26Mg systematics of type I (FeO-poor) chondrules from one of the most primitive carbonaceous chondrites, Acfer 094. The inferred initial 26Al/27Al ratios of chondrules from Acfer 094 ranged from (4.2±2.0)×10-6 to (9.0±1.5)×10-6. These chondrules have distinct oxygen isotope ratios (Δ17O: -5‰, -2‰, and 0‰), though no correlation between inferred initial 26Al/27Al ratios and oxygen isotope ratios were observed. These results indicate the regional oxygen isotope heterogeneity in the solar nebula over the duration of chondrule formation.A few low-Ca pyroxene grains in chondrules have small but resolvable 26Mg excesses at the level of ∼0.1‰, which may be the result of a partial melting of chondrules by reheating events. If this is the case, the true inferred initial 26Al/27Al ratios of these particular chondrule could be slightly lower (<10%) than estimates using Mg isotope ratios of coexisting plagioclase and olivine.Stable isotope ratios of Mg (25Mg/24Mg) of many olivine grains in chondrules are positively fractionated by ∼1‰ relative to those in other phases within the same chondrules. This suggests that olivine preserved a positively fractionated Mg isotope ratios of the chondrule-forming melt prior to significant condensation during the cooling stage of chondrule formation.
AB - We investigated the 26Al-26Mg systematics of type I (FeO-poor) chondrules from one of the most primitive carbonaceous chondrites, Acfer 094. The inferred initial 26Al/27Al ratios of chondrules from Acfer 094 ranged from (4.2±2.0)×10-6 to (9.0±1.5)×10-6. These chondrules have distinct oxygen isotope ratios (Δ17O: -5‰, -2‰, and 0‰), though no correlation between inferred initial 26Al/27Al ratios and oxygen isotope ratios were observed. These results indicate the regional oxygen isotope heterogeneity in the solar nebula over the duration of chondrule formation.A few low-Ca pyroxene grains in chondrules have small but resolvable 26Mg excesses at the level of ∼0.1‰, which may be the result of a partial melting of chondrules by reheating events. If this is the case, the true inferred initial 26Al/27Al ratios of these particular chondrule could be slightly lower (<10%) than estimates using Mg isotope ratios of coexisting plagioclase and olivine.Stable isotope ratios of Mg (25Mg/24Mg) of many olivine grains in chondrules are positively fractionated by ∼1‰ relative to those in other phases within the same chondrules. This suggests that olivine preserved a positively fractionated Mg isotope ratios of the chondrule-forming melt prior to significant condensation during the cooling stage of chondrule formation.
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U2 - 10.1016/j.gca.2013.01.045
DO - 10.1016/j.gca.2013.01.045
M3 - Article
AN - SCOPUS:84874996637
VL - 109
SP - 280
EP - 295
JO - Geochmica et Cosmochimica Acta
JF - Geochmica et Cosmochimica Acta
SN - 0016-7037
ER -