Multiple Formation of Chondrules in the Early Solar System: Chronology of a Compound Al-rich Chondrule
Multiple Formation of Chondrules in the Early Solar System: Chronology of a Compound Al-rich Chondrule
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DOI：
10.1086/512100
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发表时间：
2007-02
期刊：
影响因子：
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通讯作者：
T. Akaki;Tomoki Nakamura;T. Noguchi;A. Tsuchiyama
中科院分区：
文献类型：
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作者：
T. Akaki;Tomoki Nakamura;T. Noguchi;A. Tsuchiyama
陨石球粒是陨石的高温成分，在早期太阳系的闪热事件中形成。从存在的复合球粒，其中包括一个早期形成的单位封闭在一个较晚的阶段，它已得出结论，球粒形成事件是可重复的。我们报告的年代学的一个富铝化合物球粒从阿连德陨石，连同它的矿物学，岩相学和氧同位素组成。早期形成的原生球粒富含26 Al，初始26 Al/27 Al比值为（2.7 ± 1.0）× 10-5;晚期形成的次生球粒贫26 Al，初始26 Al/27 Al比值为（9.9 ± 2.0）× 10-6。初级和次级初始比率之间的差异相当于100万年。我们的结论是，在早期的熔融事件中形成的主要单位，并进入二次熔融，形成1万年后，在稍后的熔融事件。硅酸盐的氧同位素组成的初级和次级阶段显示不同程度的16 O-抑郁症，但类似于从阿连德陨石标本的单个球粒。因此，阿连德的这颗初级球粒在同一个尘埃库中停留了超过100万年，并经历了多次加热事件，在此期间还产生了次级球粒和单个球粒。
Chondrules are high-temperature components of meteorites and are formed during flash heating episodes in the early solar system. From the presence of compound chondrules, which consist of an early formed unit enclosed within a later phase, it has been concluded that the chondrule formation event is repeatable. We report on the chronology of one Al-rich compound chondrule from the Allende meteorite, together with its mineralogy, petrography, and oxygen isotope composition. The earlier formed primary chondrule is rich in 26Al with an initial 26Al/27Al ratio of (2.7 ± 1.0) × 10-5, whereas the later formed secondary chondrule is depleted in 26Al with an initial 26Al/27Al ratio of (9.9 ± 2.0) × 10-6. The difference between the primary and secondary initial ratios corresponds to 1 Myr. We conclude that the primary unit formed during an earlier melting episode and went into a secondary melt that formed 1 Myr later during a later melting episode. The oxygen isotope composition of silicates in the primary and secondary phases shows varying degrees of 16O-depression but is similar to that of single chondrules from Allende meteorite specimens. Therefore, this primary chondrule in Allende stayed in the same dust reservoir for over 1 Myr and experienced multiple heating events, during which secondary and single chondrules were also produced.