Transmission infrared spectra (2-25 μm) of carbonaceous chondrites (CI, CM, CV-CK, CR, C2 ungrouped): Mineralogy, water, and asteroidal processes
Transmission infrared spectra (2-25 μm) of carbonaceous chondrites (CI, CM, CV-CK, CR, C2 ungrouped): Mineralogy, water, and asteroidal processes
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DOI：
10.1016/j.icarus.2013.10.019
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发表时间：
2014-02-01
期刊：
影响因子：
3.2
通讯作者：
Schmitt, B.
中科院分区：
文献类型：
--
作者：
Beck, P.;Garenne, A.;Schmitt, B.
本文分析了40个碳质耐火材料（21个CM、5个CV、6个CR、3个CK、3个C_2和2个C_3）的红外透射光谱（2-25 μ m范围，5000-400 cm ~（-1））。已知所有这些陨石群都经历了显著的水蚀变（CKs除外）。这些红外测量提供了有关经历的母体过程的信息，以及与太阳系小天体的观测进行比较的光谱，并可能与吸积和碎片disks.This天文观测研究揭示，每个陨石群似乎有特定的签名在测量的红外光谱范围。在Cl和CM组的情况下，结果显示硅酸盐特征的形状的可变性，其可以与矿物学的演变有关，随着水蚀变程度的增加，如几位作者用其他技术所描述的。硅酸盐特征的这种演变可以在橄榄石和层状硅酸盐IR特征的相对强度的变化中看到。硅酸盐特征的变化与3-p，m处的-OH相关吸收的强度相关，这可以用于根据水合水平对陨石进行分类。有趣的是，在CM方解石的情况下，其矿物学预计由层状硅酸盐（主要是蛇纹石）主导，硅酸盐吸收的形状类似于无定形硅酸盐的形状，具有宽且对称的10（-1）μ m带，而不像陆地层状硅酸盐。从这个特征，可以确定橄榄石的平均Mg数。对于CV，橄榄石Mg数似乎以Kaba-Grosnaja-Vigarano-Mokoia-阿连德的顺序减少。这一趋势可能与这些样品经历的长期变质作用以及变质组分之间的化学再平衡有关。在CK橄榄石的情况下，推断的橄榄石的整体Mg#为67（1），并且在三个研究样品之间没有观察到变化，这可能与它们的高度平衡有关。6个CR陨石的红外光谱变化最大，从CR 1格罗夫纳山脉（GRO）95577的CM样光谱到罗伯茨山（RBT）04133和格雷夫斯冰原岛峰（GRA）06100的CV样光谱（其中一个最有可能被错误分类）。最后，这些光谱可用于与细粒小行星表面和富含尘埃的彗星尾部的发射光谱进行比较。在Tempel 1的情况下，与10-pm区域附近观察到的特征相匹配的CC的唯一组是CR组。光谱比较显示，CRs和坦普尔1号尘埃之间有一些惊人的相似之处。CR2和彗星之间的遗传联系尚未得到证实，但从红外光谱中可以看出矿物学上的相似性。(C)2013 Elsevier Inc. All rights reserved.
In this work, infrared transmission spectra (2-25 mu m range, 5000-400 cm(-1)) of 40 carbonaceous chondrites were analyzed (21 CMs, 5 CVs, 6 CRs, 3 CKs, 3 C2s and 2 Cis). All these meteorite groups are known to have experienced significant aqueous alteration (except the CKs). These IR measurements provide information about the parent body processes experienced, as well as spectra for comparison with observations of Solar System small bodies and possibly with astronomical observations of accretion and debris disks.This study reveals that each meteorite group appears to have specific signatures in the measured IR spectral range. In the case of the Cl and CM groups, results show a variability in the shape of the silicate features that can be related to the evolution of the mineralogy with increasing extent of aqueous alteration extent as described by several authors with other techniques. This evolution of the silicate feature can be seen in the variation in the relative intensities of olivine and phyllosilicate IR features. The variability in the silicate features is correlated with the intensity of an -OH related absorption at 3-p,m, which can be used for the classification of the meteorites according to the level of hydration. Interestingly, in the case of CM chondrites, for which the mineralogy is expected to be dominated by phyllosilicates (serpentine mostly), the shape of the silicate absorption resembles that of an amorphous silicate, with a broad and symmetric 10(-1) mu m band, unlike terrestrial phyllosilicates.The CV and CI( groups have IR spectra that are dominated by olivine absorption. From this feature, it is possible to determine average Mg numbers for the olivine. For the CVs, the olivine Mg numbers appear to decrease in the order Kaba-Grosnaja-Vigarano-Mokoia-Allende. This trend is likely related to the long duration of metamorphism experienced by these samples and the chemical re-equilibration between chondritic components. In the case of CK chondrites, the inferred bulk Mg# of olivine is 67 ( 1), and no variation is observed between the three studied samples, which is likely related to their high degree of equilibration. The 6 CR chondrites show the most variability in their IR spectra, from CM-like spectra in the case of the CR1 Grosvenor Mountains (GRO) 95577 to CV-like spectra for Roberts Massif (RBT) 04133 and Graves Nunataks (GRA) 06100 (one of them being most probably misclassified). Spectra of the remaining CRs show mixtures of various silicate component.Finally, these spectra can be used for comparison with emission spectra of fine-grained asteroid surfaces and dust-rich cometary tails. In the case of Tempel 1, the only group of CC that matches the observed feature around 10-pm region is the CR group. The spectral comparison shows some striking similarities between CRs and Tempel 1 dust. A genetic link between CR2 and comets is not proven, but mineralogical similarities are suggested from the IR spectra. (C) 2013 Elsevier Inc. All rights reserved.