Chondrules as direct thermochemical sensors of solar protoplanetary disk gas.
Chondrules as direct thermochemical sensors of solar protoplanetary disk gas.
复制标题
软骨作为太阳能原球磁盘气体的直接热化学传感器。
DOI：
10.1126/sciadv.aar3321
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发表时间：
2018-07
期刊：
影响因子：
13.6
通讯作者：
Portail M
中科院分区：
文献类型：
--
作者：
Libourel G;Portail M
阴极发光显示了球粒状熔体结晶过程中气体辅助外延生长的结构。球粒陨石是一种毫米大小的火成球，构成了大多数球粒陨石的主要成分，形成于太阳原行星盘演化的最初400万至500万年期间，因此，只要能够理解导致它们形成的过程，就有可能对盘中的条件提供重要的制约。对不同球粒陨石群球粒陨石的高分辨率阴极发光(CL)测量揭示了富镁橄榄石CL激活剂浓度的变化。我们发现，这些被忽视的内部分带结构为橄榄石球粒形成过程中高温气体辅助的近平衡外延生长提供了证据。我们认为，这种与周围气体的相互作用，而不是各种冷却历史，定义了球粒陨石的成分和结构。因此，球粒陨石是其高温气体环境的直接热化学传感器，在其太阳原行星盘形成区，需要高分压的气体镁和二氧化硅来维持球粒陨石中的橄榄石饱和度。从与周围气体接近平衡的稳定熔体中推断出橄榄石的结晶，为球粒陨石中显著缺乏大而系统的同位素分馏提供了解释。
Cathodoluminescence reveals structures indicative of gas-assisted epitaxial growth during chondrule melt crystallization. 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.
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影响因子：
5
作者：
Ebel, DS;Grossman, L
通讯作者：
Grossman, L
影响因子：
5
作者：
Eugenia Varela, Maria;Zinner, Ernst
通讯作者：
Zinner, Ernst
影响因子：
3.9
作者：
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通讯作者：
Libourel, Guy
影响因子：
2.7
作者：
KUPHAL, E
通讯作者：
KUPHAL, E
影响因子：
5
作者：
LOFGREN, G
通讯作者：
LOFGREN, G