Abstract A ∼175 µm refractory inclusion, A-COR-01 from one of the least altered carbonaceous chondrites, ALHA 77307 (CO3.0), has been found to bear unique characteristics that indicate that it is one of the first solids to have formed at the very birth of the solar system while isotopic reservoirs were still evolving rapidly. Its core is composed mainly of hibonite and corundum, the two phases predicted to condense first from a gas of solar composition, and like many common types of Calcium-, Aluminium-rich Inclusions (CAIs) is surrounded by a rim of diopside. Core minerals in A-COR-01 are very 16O-rich (Δ17OCore = −32.5 ± 3.3 (2SD) ‰) while those in the rim display an O isotopic composition (Δ17ORim = −24.8 ± 0.5 (2SD) ‰) indistinguishable from that found in the vast majority of the least altered CAIs. These observations indicate that this CAI formed in a very 16O-rich reservoir and either recorded the subsequent evolution of this reservoir or the transit to another reservoir. The origin of A-COR-01in a primitive reservoir is consistent with the very low content of excess of radiogenic 26Mg in its core minerals corresponding to the inferred initial 26Al/27Al ratio ((26Al/27Al)0 = (1.67 ± 0.31) × 10−7), supporting a very early formation before injection and/or homogenisation of 26Al in the protoplanetary disk. Possible reservoir evolution and short-lived radionuclide (SLRs) injection scenarios are discussed and it is suggested that the observed isotope composition resulted from mixing of a previously un-observed early reservoir with the rest of the disk.

中文翻译：

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最早的耐火包裹体之一及其对太阳系历史的影响

摘要 来自变化最少的碳质球粒陨石 ALHA 77307 (CO3.0) 的约 175 µm 耐火夹杂物 A-COR-01 具有独特的特性，表明它是最早形成的固体之一。在太阳系诞生之初，同位素库仍在迅速发展。它的核心主要由黑曜石和刚玉组成，预计这两个相首先由太阳成分的气体凝结而成，并且像许多常见类型的富含钙、铝的包裹体 (CAI) 一样被透辉石边缘包围。A-COR-01 中的核心矿物非常富含 16O (Δ17OCore = -32.5 ± 3.3 (2SD) ‰)，而边缘的那些显示 O 同位素组成 (Δ17ORim = -24.8 ± 0.5 (2SD) ‰) 与此无法区分在绝大多数变化最小的 CAI 中发现。这些观察结果表明，该 CAI 形成于一个富含 16O 的储层，并且记录了该储层的后续演化或向另一个储层的过渡。原始储层中 A-COR-01 的起源与其核心矿物中超低含量的放射成因 26Mg 一致，对应于推断的初始 26Al/27Al 比值 ((26Al/27Al)0 = (1.67 ± 0.31) × 10-7)，支持在原行星盘中注入和/或均质化 26Al 之前的非常早的形成。讨论了可能的储层演化和短寿命放射性核素 (SLR) 注入场景，并提出观察到的同位素组成是由先前未观察到的早期储层与圆盘其余部分混合引起的。