Investigation of organo-carbonate associations in carbonaceous chondrites by Raman spectroscopy
Investigation of organo-carbonate associations in carbonaceous chondrites by Raman spectroscopy
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DOI：
10.1016/j.gca.2016.10.048
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发表时间：
2017-03-15
影响因子：
5
通讯作者：
Cheung, Jacob C. H.
中科院分区：
文献类型：
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作者：
Chan, Queenie H. S.;Zolensky, Michael E.;Cheung, Jacob C. H.
碳酸盐记录了在水蚀变事件期间通过小行星母体循环的流体的时间、性质和条件的信息。确定碳酸盐丰度及其与有机质的关系，提高了我们的理解的成因的主要碳质成分在南极洲的材料。在这项研究中，五个CM 2碳质碳酸盐（CM 2.2 Nogoya，CM 2.3 Jbilet Winselwan，CM 2.5 Murchison，CM 2圣克鲁斯，和CM 2 TII威斯康星州范围91600）进行了研究与拉曼光谱。通过在1100 cm（-1）区域的独特拉曼谱带（代表（CO3）（2-）阴离子的对称伸缩振动模式（nu（1），在这些陨石样品中鉴定出碳酸盐。在陨石样本中发现的碳酸盐都是方解石，除了Nogoya的一个白云石颗粒。CM方解石的v（1）位置比纯方解石高2 - 3 cm（-1），这表明它们含有大量的杂质阳离子。典型的石墨一阶D和G带被确定在陨石基质以及在类似的25%的分析碳酸盐颗粒。从拉曼的结果，我们假设，碳酸盐可能没有形成在平衡条件下从一个单一的流体。第一代碳酸盐被解释为形成于高度氧化的流体，导致有机质（OM）的氧化，并产生OM贫瘠的碳酸盐。第二代碳酸盐岩是在有机质的存在下，由更演化的含水流体形成的。碳酸盐中有机物的拉曼参数明显偏离基质OM，这表明碳酸盐有机物含有非常不同的含碳组分，其不同于CM基质的典型无定形OM。不同世代的碳酸盐的出现可能是部分原因，在过去的研究中报告的碳质泥岩中碳酸盐的估计年龄范围很大。(C)2016由Elsevier Ltd.出版
Carbonates record information regarding the timing, nature and conditions of the fluids circulating through asteroid parent bodies during aqueous alteration events. Determining carbonate abundances and their relationships with organic matter improves our understanding of the genesis of major carbonaceous components in chondritic materials. In this study, five CM2 carbonaceous chondrites (CM2.2 Nogoya, CM2.3 Jbilet Winselwan, CM2.5 Murchison, CM2 Santa Cruz, and CM2TII Wisconsin Range 91600) were studied with Raman spectroscopy. Carbonates were identified in these meteorite samples by the distinctive Raman band in the similar to 1100 cm(-1) region, representing the symmetric stretching vibration mode (nu(1)) of the (CO3)(2-) anion. Carbonates identified in the meteorite samples are all calcite, with the exception of a single dolomite grain in Nogoya. The v(1) positions of the CM calcites are 2-3 cm(-1) higher than in pure calcite, which suggests that they contain significant impurity cations. Typical graphitic first-order D and G bands were identified in the meteorite matrix as well as in similar to 25% of the analyzed carbonate grains. From the Raman results, we postulate that the carbonates might not have formed under equilibrium conditions from a single fluid. The first generation of carbonate is interpreted to have formed from highly oxidized fluids that led to the oxidation of organic matter (OM) and produced carbonates that are OM-barren. The second generation of carbonate was formed from a more evolved aqueous fluid with the presence of OM. The Raman parameters of the organics in carbonates clearly deviate from the matrix OM which suggests that the carbonate organics contain very different carbonaceous components that are distinct from the typical amorphous OM of the CM matrix. The occurrence of different generations of carbonate in close proximity may be partly responsible for the wide range in estimated ages of carbonates in carbonaceous chondrites reported in previous studies. (C) 2016 Published by Elsevier Ltd.