The abundance and stability of "water" in type 1 and 2 carbonaceous chondrites (CI, CM and CR)
The abundance and stability of "water" in type 1 and 2 carbonaceous chondrites (CI, CM and CR)
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DOI：
10.1016/j.gca.2014.03.034
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发表时间：
2014-07-15
影响因子：
5
通讯作者：
Schmitt, B.
中科院分区：
文献类型：
--
作者：
Garenne, A.;Beck, P.;Schmitt, B.
碳质球粒陨石记录了水合和羟基化矿物存在下的水蚀变过程，这可能为太阳系内部提供了水源（Alexander et al., 2012, 2013）。在这项研究中，对 26 CM 球粒陨石进行了热重分析 (TGA)，以量化其水含量，这些球粒陨石涵盖了从 2.0（如陨石山 (MET) 01070）到 2.6（如亚历山德拉女王山脉 (QUE) 97990）的水蚀变程度。此外，通过测量挥发性元素的释放随温度的变化，我们获得了含水相的矿物学信息，并提供了基于页硅酸盐释放的水的水蚀变指标。这些分析与对加热至 300 摄氏度的陨石颗粒进行的红外光谱 (IR) 相结合。红外特征（-OH 波段为 3 微米，SiO4 约为 10 微米）揭示了与 TGA 的相关性。这两种技术与 Rubin 等人提出的水蚀蚀方案一致。 （2007）和亚历山大等人。 (2013) 基于页硅酸盐丰度。TGA 中观察到的低温（200-400 摄氏度）质量损失归因于铁氧氢氧化物（水铁矿、针铁矿）。然而，这些由陆地蚀变形成的矿物的比例仍然未知。 TGA 还揭示了两种异常 CM 球粒陨石，Pecora Escarpment (PCA) 02012 和 PCA 02010。它们的 TGA 曲线与质量损失很少的“常规”CM 球粒陨石显着不同，这可能与这些陨石响应加热事件的脱水历史有关（拉曼测量也指向热事件，Quirico 等人，2013）。对于较温和加热的球粒陨石，例如威斯康星山脉 (WIS) 91600，TGA 曲线呈现出与其他 CM 相似的质量损失。 TGA 还研究了 CR 球粒陨石的 7 次整体测量和 CR 陨石基质富集部分的 3 次测量，并证实了球粒的低水合水平和基质的显着变化。估算了 CM 2.6 QUE 97990 基质的水含量，并将其与 CR2 EET 92159 基质富集部分和 Orgueil 的 TGA 进行比较。结果表明 Orgueil 和 CM 基质之间的水性改变程度相似（约 25 wt.%），而 CR2 基质的改变较低（11 wt.% H2O）。 (C) 2014 Elsevier Ltd. 保留所有权利。
Carbonaceous chondrites record processes of aqueous alteration in the presence of hydrated and hydroxylated minerals, which could have provided a source of water in the inner solar system (Alexander et al., 2012, 2013). In this study, thermogravimetric analysis (TGA) was performed on 26 CM chondrites, which cover a range of degree of aqueous alteration from 2.0, such as Meteorite Hills (MET) 01070, to 2.6, such as Queen Alexandra Range (QUE) 97990, in order to quantify their water content. In addition, by measuring the release of volatile elements as a function of temperature, we obtained information on the mineralogy of water-bearing phases and provide indicators of aqueous alteration based on water released by phyllosilicates. These analyses are combined with infrared spectroscopy (IR) made on meteorite pellets heated up to 300 degrees C. The infrared features (-OH band at 3-mu m and SiO4 around 10-mu m) revealed a correlation with TGA. The two techniques are in agreement with the scheme of aqueous alteration proposed by Rubin et al. (2007) and Alexander et al. (2013) based on phyllosilicate abundance.The low temperature (200-400 degrees C) mass loss observed in TGA is attributed to Fe-oxy-hydroxydes (ferrihydrite, goethite). However, the proportion of these minerals formed by terrestrial alteration remains unknown. TGA also revealed two anomalous CM chondrites, Pecora Escarpment (PCA) 02012 and PCA 02010. Their TGA curves are significantly different from those of "regular" CMs with little mass loss, which can be related to the dehydration history of these meteorites in response to a heating event (Raman measurements also point toward a thermal event, Quirico et al., 2013). In the case of more mildly heated chondrites, such as with Wisconsin Range (WIS) 91600, the TGA curve presents similar mass loss to the other CMs.Seven bulk measurements of CR chondrites and 3 measurements of matrix-enriched parts of CR meteorites were also studied by TGA, and confirm the low hydration level of chondrules and a significant alteration of the matrix. The water content of the matrix of the CM 2.6 QUE 97990 was estimated and compared to TGA of the matrix enriched portion of the CR2 EET 92159 and that of Orgueil.Results suggest a similar aqueous alteration degree between Orgueil and the matrix of CMs (around 25 wt.%) and a lower alteration of the CR2 matrix (11 wt.% of H2O). (C) 2014 Elsevier Ltd. All rights reserved.