We report microscopic, cathodoluminescence, chemical, and O isotopic measurements of FeO‐poor isolated olivine grains (IOG) in the carbonaceous chondrites Allende (CV3), Northwest Africa 5958 (C2‐ung), Northwest Africa 11086 (CM2‐an), and Allan Hills 77307 (CO3.0). The general petrographic, chemical, and isotopic similarity with bona fide type I chondrules confirms that the IOG derived from them. The concentric CL zoning, reflecting a decrease in refractory elements toward the margins, and frequent rimming by enstatite are taken as evidence of interaction of the IOG with the gas as stand‐alone objects. This indicates that they were splashed out of chondrules when these were still partially molten. CaO‐rich refractory forsterites, which are restricted to ∆17O <−4‰ likely escaped equilibration at lower temperatures because of their large size and possibly quicker quenching. The IOG thus bear witness to frequent collisions in the chondrule‐forming regions.

中文翻译：

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碳质球粒陨石中分离橄榄石颗粒的起源

我们报告了对碳质球粒陨石阿连德 (CV3)、西北非洲 5958 (C2-ung)、西北非洲 11086 (CM2-an) 和艾伦山 77307 (CO3.0)。与真正的 I 型球粒的一般岩相学、化学和同位素相似性证实了 IOG 源自它们。同心的 CL 分带，反映了耐火元素向边缘的减少，以及顽火石的频繁边缘，被视为 IOG 与作为独立物体的气体相互作用的证据。这表明它们是在球粒仍部分熔化时从球粒中飞溅出来的。富含 CaO 的耐火镁橄榄石，仅限于 ∆17O < -4‰ 可能在较低温度下逃脱平衡，因为它们的尺寸较大且淬火可能较快。因此，IOG 见证了球粒形成区域的频繁碰撞。