Paris vs. Murchison: Impact of hydrothermal alteration on organic matter in CM chondrites
Paris vs. Murchison: Impact of hydrothermal alteration on organic matter in CM chondrites
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Paris 与 Murchison：热液蚀变对 CM 球粒陨石中有机质的影响
DOI：
10.1016/j.gca.2017.06.009
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发表时间：
2017
影响因子：
5
通讯作者：
L. Remusat
中科院分区：
文献类型：
--
作者：
V. Vinogradoff;C. Guillou;S. Bernard;L. Binet;P. Cartigny;A. Brearley;L. Remusat
要弄清附着在小行星上的有机化合物的来源，需要更好地限制小行星热液蚀变对其同位素特征、分子结构和空间分布的影响。在这里，我们对两个经历了不同程度的热液蚀变的CM球粒陨石(来自同一母体或来自相同母体的相同母体)的有机质(OM)进行了多尺度/多技术的对比研究：Paris(蚀变较弱的CM球粒陨石-CM 2.8)和Murchison(蚀变较大的CM 2.5)。与Murchison不溶有机物相比，巴黎不溶有机物表现出较高的脂肪/芳烃碳比、较高的自由基丰度和较低的氧含量。对OMin现场的分析表明，巴黎基质中存在两组结构不同的有机化合物：亚微米级的单个OM颗粒和弥漫的OM，它们细小地分布在层状硅酸盐和无定形硅酸盐中。这些结果表明，CM母体上的水热蚀变导致了IOM的芳构化和氧化，并降低了自由基和氮的含量。其中一些观测也是通过对塔吉什湖(C2)可变蚀变碎屑的研究报告的，尽管塔吉什湖OM的热液蚀变显然要严重得多。最后，与文献资料的对比表明，其他球粒陨石岩群的母体可能聚集了一种与CMS母体不同的有机前体混合物。
Unravelling the origin of organic compounds that were accreted into asteroids requires better constraining the impact of asteroidal hydrothermal alteration on their isotopic signatures, molecular structures, and spatial distribution. Here, we conducted a multi-scale/multi-technique comparative study of the organic matter (OM) from two CM chondrites (that originate from the same parent body or from identical parent bodies that accreted the same mixture of precursors) and underwent a different degree of hydrothermal alteration: Paris (a weakly altered CM chondrite – CM 2.8) and Murchison (a more altered one – CM 2.5). The Paris insoluble organic matter (IOM) shows a higher aliphatic/aromatic carbon ratio, a higher radical abundance and a lower oxygen content than the Murchison IOM. Analysis of the OMin situshows that two texturally distinct populations of organic compounds are present within the Paris matrix: sub-micrometric individual OM particles and diffuse OM finely distributed within phyllosilicates and amorphous silicates. These results indicate that hydrothermal alteration on the CM parent body induced aromatization and oxidation of the IOM, as well as a decrease in radical and nitrogen contents. Some of these observations were also reported by studies of variably altered fragment of Tagish Lake (C2), although the hydrothermal alteration of the OM in Tagish Lake was apparently much more severe. Finally, comparison with data available in the literature suggests that the parent bodies of other chondrite petrologic groups could have accreted a mixture of organic precursors different from that accreted by the parent body of CMs.