Evolution of organic matter in Orgueil, Murchison and Renazzo during parent body aqueous alteration: In situ investigations
Evolution of organic matter in Orgueil, Murchison and Renazzo during parent body aqueous alteration: In situ investigations
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DOI：
10.1016/j.gca.2013.11.020
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发表时间：
2014-04-15
影响因子：
5
通讯作者：
Remusat, Laurent
中科院分区：
文献类型：
--
作者：
Le Guillou, Corentin;Bernard, Sylvain;Remusat, Laurent
球粒陨石吸积了太阳系中最古老的固体物质，包括在原行星盘中处理的尘埃和各种有机化合物。在吸积之后，小行星蚀变可能以各种方式影响有机颗粒。为了限制这些过程，我们对Renazzo（CR 2）、Murchison（CM 2）和Orgueil（CI）这三个碳质球粒陨石福尔斯的基质中散布的有机物进行了全面研究。通过结合基于同步加速器的STXM和TEM分析的FIB部分的样品先前表征的NanoSIMS，我们研究了含水蚀变的形态，同位素特征，分子结构，空间分布和矿物学环境的有机质内的矩阵的影响。两种不同的材料群体是可区分的：亚微米的单个颗粒，可能主要由不溶性化合物和扩散的有机物质，精细地散布在纳米尺度的页硅酸盐和/或（无定形）纳米碳酸盐内。我们认为，后者的组成部分，这是耗尽的芳香族化合物和丰富的羧基官能团，可能是由可溶性化合物为主。Renazzo（CR）中的有机质主要由化学均匀的单个颗粒组成，这些颗粒被无定形和纳米晶层状硅酸盐包围。有机颗粒和裂缝之间连通性的证据表明，发生了重新分布：可以观察到一些含有弥散有机质的区域。这种弥漫性有机成分在Murchison（CM）和Orgueil（CI）中更丰富。这被解释为导致在微米尺度和重结晶蚀变相内的封装流体输送。与Renazzo相反，Murchison和Orgueil的有机颗粒显示出强烈的化学不均匀性，可能与水蚀变过程中的化学演化有关。观察结果表明，改变流体是具有升高的有机和无机可溶性组分浓度的盐水。最终，当水被水蚀变反应消耗或从系统中损失时，可溶性有机化合物在沉淀的碳酸盐和磷酸盐的紧邻处积累。此外，纳米尺度的有机/页硅酸盐关系提供了一个岩石学环境，其中一些最初增生的有机物质可能已经通过粘土介导的反应进行了修改。(C)2013爱思唯尔有限公司保留所有权利。
Chondrites accreted the oldest solid materials in the solar system including dust processed in the protoplanetary disk and diverse organic compounds. After accretion, asteroidal alteration may have impacted organic particles in various ways. To constrain these processes, we conducted a comprehensive study of organics disseminated within the matrices of the three carbonaceous chondrite falls, Renazzo (CR2), Murchison (CM2) and Orgueil (CI). By combining synchrotron-based STXM and TEM analyses on FIB sections of samples previously characterized by NanoSIMS, we investigated the influence of aqueous alteration on the morphology, isotopic signature, molecular structure, spatial distribution, and mineralogical environment of the organic matter within the matrices. Two different populations of materials are distinguishable: sub-micrometric individual grains, likely dominated by insoluble compounds and diffuse organic matter, finely interspersed within phyllosilicates and/or (amorphous) nanocarbonates at the nanometer scale. We suggest that this latter component, which is depleted in aromatics and enriched in carboxylic functional groups, may be dominated by soluble compounds. Organic matter in Renazzo (CR) mainly consists of chemically-homogeneous individual grains surrounded by amorphous and nanocrystalline phyllosilicates. Evidence of connectivity between organic grains and fractures indicates that redistribution has occurred: some areas containing diffuse organic matter can be observed. This diffuse organic component is more abundant in Murchison (CM) and Orgueil (CI). This is interpreted as resulting from fluid transport at the micrometer scale and encapsulation within recrystallized alteration phases. In contrast to Renazzo, organic grains in Murchison and Orgueil display strong chemical heterogeneities, likely related to chemical evolution during aqueous alteration. The observations suggest that the altering fluid was a brine with elevated concentrations of both organic and inorganic soluble components. Ultimately, when water was consumed by aqueous alteration reactions or lost from the system, soluble organic compounds accumulated in the immediate vicinity of the precipitated carbonates and phosphates. Additionally, the nanometer scale organic/phyllosilicate relationships provide a petrological environment where some of the initially accreted organic matter could have been modified through clay-mediated reactions. (C) 2013 Elsevier Ltd. All rights reserved.