CM carbonaceous chondrite falls and their terrestrial alteration
CM carbonaceous chondrite falls and their terrestrial alteration
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CM碳质球粒陨石坠落及其陆地蚀变
DOI：
10.1111/maps.13607
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发表时间：
2021
影响因子：
2.2
通讯作者：
Lee M
中科院分区：
文献类型：
--
作者：
Lee M
CM碳质球粒陨石提供了对原行星盘的组成、其母C-复合体小行星(S)的吸积作用和地质历史的独特见解。在数百种可供研究的CMS中，大多数是已发现的，因此可能受到了陆地风化的影响。从1838年到2020年，已经恢复了19个瀑布，而且有迹象表明存在两个时间集群：1930-1942年和2009-2020年。瀑布被认为比发现更适合研究，因为它们应该接近原始状态，这里通过调查它们在恢复之前和修复过程中对变化的敏感性来检验这一假设。落在地表的CMS很容易被土壤和植被中的有机化合物污染。在收集之前暴露在液态水中的矿物，包括奥德姆铁矿在内的矿物可以被溶解，大多数流动元素被淋失。在恢复的几天内，CMS从大气中吸收水，通常被空气中的碳氢化合物污染。在一年到十年的时间尺度上，与大气中的水和氧的相互作用可以从铁、镍金属中产生氢氧化铁，从本地石膏和老石膏中产生石膏。1970年前瀑布的岩石学(亚)类型与它们的陆地年龄之间的关系可能是由于在管理过程中广泛但隐蔽的变化，但更有可能是采样偏差。在利用CM瀑布推断Ryugu和Bennu等C-复杂母体的过程之前，必须考虑CM瀑布的陆地历史，包括它的收集情况和管理条件。
The CM carbonaceous chondrites provide unique insights into the composition of the protoplanetary disk, and the accretion and geological history of their parent C‐complex asteroid(s). Of the hundreds of CMs that are available for study, the majority are finds and so may have been compromised by terrestrial weathering. Nineteen falls have been recovered between 1838 and 2020, and there is a hint of two temporal clusters: 1930–1942 and 2009–2020. Falls are considered preferable to finds to study because they should be near pristine, and here this assumption is tested by investigating their susceptibility to alteration before recovery and during curation. CMs falling on the land surface are prone to contamination by organic compounds from soil and vegetation. Where exposed to liquid water prior to collection, minerals including oldhamite can be dissolved and most fluid mobile elements leached. Within days of recovery, CMs adsorb water from the atmosphere and are commonly contaminated by airborne hydrocarbons. Interaction with atmospheric water and oxygen during curation over year to decadal timescales can produce Fe‐oxyhydroxides from Fe,Ni metal and gypsum from indigenous gypsum and oldhamite. Relationships between the petrologic (sub)types of pre‐1970 falls and their terrestrial age could be due to extensive but cryptic alteration during curation, but are more likely a sampling bias. The terrestrial history of a CM fall, including circumstances of its collection and conditions of its curation, must be taken into account before it is used to infer processes on C‐complex parent bodies such as Ryugu and Bennu.
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