Nucleosynthetic components of the early solar system inferred from Ba isotopic compositions in carbonaceous chondrites
Nucleosynthetic components of the early solar system inferred from Ba isotopic compositions in carbonaceous chondrites
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DOI：
10.1016/s0012-821x(03)00393-5
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发表时间：
2003-09-30
影响因子：
5.3
通讯作者：
Yoneda, S
中科院分区：
文献类型：
--
作者：
Hidaka, H;Ohta, Y;Yoneda, S
原始陨石的Ba同位素组成是研究早期太阳系核合成过程的最有用的示踪剂之一，因为Ba的七种稳定同位素包括p-、r-和s-过程的核合成成分，以及目前已灭绝的Cs-135的可能衰变产物。对五种碳质无球粒陨石Murchison（CM 2）、狭山（CM 2）、阿连德（CV 3）、Isuna（CO 3）和Maralinga（CK 4）和一种玄武质无球粒陨石Juvinas（Eucrite）的酸浸出液进行了Ba同位素分析。酸处理馏分中的碳质玄武岩的Ba同位素数据表明，在太阳系中的S-和R-过程的独立的核合成成分的存在。从两个CM 2陨石，Murchison和狭山，酸残留馏分的同位素模式，显示富集的S-过程同位素，这是类似的前太阳SiC颗粒。另一方面，它们的酸浸出液中Ba同位素中含有过量的r-过程成分。在许多情况下，除了CM陨石外，碳质陨石的r过程同位素过量太小，无法详细讨论核合成的贡献。这可能被解释为与岩相型陨石有关的陨石基质中太阳前颗粒的变质破坏。Juvinas没有显示Ba的同位素异常，因为早期太阳系的同位素记录可能被母体中的岩浆过程重置。(C)2003 Elsevier B. V.保留所有权利。
The Ba isotopic composition of primitive meteorites is one of the more useful tracers to study nucleosynthetic processes in the early solar system, because the seven stable Ba isotopes consist of p-, r-, and s-process nucleosynthetic components and possible decay products from presently extinct Cs-135. Ba isotopic analyses were performed on acid leachates from five carbonaceous chondrites, Murchison (CM2), Sayama (CM2), Allende (CV3), Isuna (CO3) and Maralinga (CK4), and one basaltic achondrite, Juvinas (Eucrite). The Ba isotopic data of acid treatment fractions in carbonaceous chondrites suggest the presence of independent nucleosynthetic components for s- and r-processes in the solar system. The isotopic patterns from the acid residual fractions of two CM2 meteorites, Murchison and Sayama, show an enrichment of s-process isotopes, which is similar to that of presolar SiC grains. On the other hand, their acid leachates have an excess of r-process components among the Ba isotopes. In many cases of carbonaceous chondrites other than CM meteorites, the excess of r-process isotopes is too small for a detailed discussion about the nucleosynthetic contribution. This may be interpreted as metamorphic destruction of presolar grains in meteorite matrices associated with petrographic-type meteorites. Juvinas shows no isotopic anomalies of Ba, because the isotopic record in the early solar system was reset possibly by magmatic processes in the parent body. (C) 2003 Elsevier B.V. All rights reserved.