Chondrules, millimeter-sized igneous spherules comprising the major component of most chondritic meteorites, formed during the first 4 million to 5 million years of the evolution of the solar protoplanetary disk and, therefore, can potentially offer important constraints on the conditions in the disk, provided that the processes that led to their formation can be understood. High-resolution cathodoluminescence (CL) survey of chondrules from various chondrite groups revealed changes of CL activator concentrations of magnesium-rich olivines. We show that these overlooked internal zoning structures provide evidence for high-temperature gas-assisted near-equilibrium epitaxial growth of olivines during chondrule formation. We argue that this interaction with the surrounding gas, rather than various cooling histories, defined chondrule composition and texture. Chondrules are thus direct thermochemical sensors of their high-temperature gaseous environment, and high partial pressures of gaseous Mg and SiO are required in their solar protoplanetary disk-forming region to maintain olivine saturation in chondrules. The inferred crystallization of olivines, from stable melts approaching equilibrium with the surrounding gas, provides an explanation for the notable absence of large and systematic isotopic fractionations in chondrules.

中文翻译：

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圆弧作为太阳原行星盘气体的直接热化学传感器。

球状星团，是大多数软骨陨石的主要成分，毫米大小的火成球，形成于太阳原行星盘发展的前四百万到五百万年，因此可能对盘中的状况提供重要的限制，只要可以理解导致其形成的过程。各种球粒陨石群的球粒的高分辨率阴极发光（CL）调查显示，富含镁的橄榄石的CL活化剂浓度发生了变化。我们显示，这些被忽视的内部分区结构为软骨形成过程中橄榄石的高温气体辅助近平衡外延生长提供了证据。我们认为与周围气体的这种相互作用，而不是各种冷却历史，定义软骨成分和质地。因此，软骨是其高温气态环境的直接热化学传感器，并且在其太阳原行星盘形成区域中需要气态Mg和SiO的高分压，以保持软骨中橄榄石的饱和度。橄榄石的结晶是从稳定的熔体与周围的气体达到平衡而得出的，这为软骨中明显缺乏大而系统的同位素分馏提供了解释。