We examined 16 white opaque inclusions exposed on two polished slices of a Muong Nong‐type Australasian tektite from Muong Phin, Laos. The inclusions usually consist of a core, surrounded by a froth layer, and a quartz neoblast layer. The cores are composed primarily of a mixture of silica glass, coesite, and quartz in varying proportions. A thin (up to ~4 μm) layer of SiO₂‐poor glass enriched in FeO, MgO, CaO, Al₂O₃, and TiO₂ is observed as a bright halo in backscattered electron images around the quartz neoblasts and in places contains μm‐sized crystals, which may be Fe,Mg‐rich spinel. The distribution and textural relationships between the coesite‐bearing inclusions and the tektite matrix point to an in situ formation of the coesite due to an impact, rather than to infall, from a nearby impact, into tektite melt produced by the aerial burst of a bolide. The quartz neoblasts probably formed by crystallization of silica melt squeezed out of the inclusion core during the development of the froth layer. The bright halo may be the result of silica diffusing from the adjacent tektite melt into the growing quartz neoblasts. We propose that the survival of coesite was possible due to the froth layer that acted as a heat sink during bubble expansion and then as a thermal insulator.

中文翻译：

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老挝Muong Phin的Muong Nong型陨石中的Coesite：描述，形成和生存

我们检查了16个白色不透明夹杂物，它们暴露在来自老挝Muong Phin的Muong Nong型澳大利亚陨石的两个抛光切片上。夹杂物通常由被泡沫层包围的芯和石英新胚层组成。纤芯主要由不同比例的石英玻璃，堇青石和石英的混合物组成。贫化的SiO ₂薄玻璃层（约4μm），富含FeO，MgO，CaO，Al ₂ O ₃和TiO ₂在石英新胚细胞周围的反向散射电子图像中观察到明亮的光晕，并且在某些地方含有μm大小的晶体，可能是富含Fe，Mg的尖晶石。载有堇青石的夹杂物与陨石基质之间的分布和结构关系表明，由于撞击而不是由于附近的撞击而落入硼化物的空中爆炸所产生的陨石熔体中，导致了陨石的原位形成。 。在泡沫层形成过程中，石英新生胚可能是由硅熔体结晶从包裹核中挤出而形成的。明亮的光晕可能是二氧化硅从相邻的陨石熔体扩散到生长的石英新胚层中的结果。