The mechanism of gas-melt interactions and the compositions of precursors are key to understanding the formation of chondrules. To shed light on the two enigmas, we studied the petrography, chemistry, and oxygen isotopes of six Al-rich chondrules (ARCs, five glassy and one plagioclase-bearing) in unequilibrated ordinary chondrites (OCs, petrologic subtype: 3.05). The plagioclase-bearing ARC was also investigated with Al-Mg chronology. Elemental zonation and inter-element correlations in glassy mesostasis of two ARCs indicate the condensation of gaseous Mg, SiO, Fe, and Na onto chondrule melt. The plagioclase-bearing ARC appears to display internal mass-independent oxygen isotope fractionation with δO increasing following the order of mineral crystallization, suggesting partial oxygen isotope exchange with ambient gas during crystallization. Oxygen isotopes of the six ARCs are distributed along a mixing line of slope = 0.99 ± 0.05, which intersects with calcium-aluminum-rich inclusions (CAIs), consistent with a small portion of OC type IA chondrules, but deviates from other OC ferromagnesium chondrules (FMCs) towards higher δO, suggesting that OC ARCs and some IA chondrules were established by interactions between CAI-like melts and O-poor ambient gas, rather than simply remelting solid mixtures of CAI and FMC materials.

中文翻译：

---

通过类 CAI 熔体与环境气体的相互作用锻造内盘富铝球粒


气体熔体相互作用的机制和前体的组成是理解球粒形成的关键。为了解开这两个谜团，我们研究了不平衡的普通球粒陨石（OC，岩石学亚型：3.05）中的六个富铝球粒（ARC，五个玻璃质和一个斜长石）的岩相学、化学和氧同位素。还用 Al-Mg 年代学研究了含有斜长石的 ARC。两个 ARC 的玻璃态介稳态中的元素分带和元素间相关性表明气态 Mg、SiO、Fe 和 Na 凝结到球粒熔体上。含有斜长石的 ARC 似乎表现出内部与质量无关的氧同位素分馏，其中 δ18O 按照矿物结晶的顺序增加，表明在结晶过程中与环境气体进行了部分氧同位素交换。 6个ARC的氧同位素沿斜率=0.99±0.05的混合线分布，该混合线与富钙铝包裹体（CAI）相交，与一小部分OC IA型球粒一致，但与其他OC铁镁球粒不同（FMC）朝向更高的 δ18O，这表明 OC ARC 和一些 IA 球粒是通过类 CAI 熔体和贫氧环境气体之间的相互作用建立的，而不是简单地重熔 CAI 和 FMC 材料的固体混合物。