Characterising the CI and CI-like carbonaceous chondrites using thermogravimetric analysis and infrared spectroscopy
Characterising the CI and CI-like carbonaceous chondrites using thermogravimetric analysis and infrared spectroscopy
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DOI：
10.1186/s40623-015-0370-4
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发表时间：
2015-12-09
影响因子：
3
通讯作者：
Russell, Sara S.
中科院分区：
文献类型：
--
作者：
King, Ashley J.;Solomon, Jake R.;Russell, Sara S.
CI和类CI陨石提供了太阳系早期水蚀变的记录。然而，CI类榴辉岩的不同之处在于也经历了热变质的晚期阶段。为了限制的性质和程度的水和热蚀变，我们已经调查了大量的矿物学和丰富的水在CI和CI-样方解石，使用热重分析和红外光谱。C1-C10的Ivuna和Orgueil显示出显著的质量损失（28.5-31.8重量%）。在加热至1000 ℃时，由于大量层状硅酸盐和Fe-（氧）氢氧化物的脱水和脱羟基以及Fe-硫化物、碳酸盐和有机物的分解，Ivuna和Orgueil的红外光谱有一个突出的3-μ m的功能，由于结合-OH/H2O在层状硅酸盐和Fe-（氧）氢氧化物和只有一个轻微的11-μ m的功能，从无水硅酸盐。这些特征与先前的研究一致，表明CI方解石经历了近乎完全的水蚀变。水的总丰度和3 μ m/11 μ m比值的相似性表明，Ivuna和Orgueil经历的相对水化程度没有差异。相反，CI样矿物Y-82162和Y-980115显示出较低的质量损失（13.8-18.8 wt.%）。并且含有比C1沸石少> 50%的H2O。Y-82162和Y-980115的光谱中几乎不存在3 μ m特征，但11 μ m特征很强。Cl-状方解石在>500摄氏度的温度下经历热变质作用，其最初引起页硅酸盐的脱水和脱羟基化，然后部分重结晶回到无水硅酸盐。许多C-型小行星的表面可能因撞击变质作用和/或太阳辐射而被加热，因此热蚀变的碳质陨石很可能是隼鸟2号和OSIRIS-REx飞行任务返回的样本的良好类似物。
The CI and CI-like chondrites provide a record of aqueous alteration in the early solar system. However, the CI-like chondrites differ in having also experienced a late stage period of thermal metamorphism. In order to constrain the nature and extent of the aqueous and thermal alteration, we have investigated the bulk mineralogy and abundance of H2O in the CI and CI-like chondrites using thermogravimetric analysis and infrared spectroscopy. The CI chondrites Ivuna and Orgueil show significant mass loss (28.5-31.8 wt.%) upon heating to 1000 degrees C due to dehydration and dehydroxylation of abundant phyllosilicates and Fe-(oxy) hydroxides and the decomposition of Fe-sulphides, carbonates and organics. Infrared spectra for Ivuna and Orgueil have a prominent 3-mu m feature due to bound -OH/H2O in phyllosilicates and Fe-(oxy) hydroxides and only a minor 11-mu m feature from anhydrous silicates. These characteristics are consistent with previous studies indicating that the CI chondrites underwent near-complete aqueous alteration. Similarities in the total abundance of H2O and 3 mu m/11 mu m ratio suggest that there is no difference in the relative degree of hydration experienced by Ivuna and Orgueil.In contrast, the CI-like chondrites Y-82162 and Y-980115 show lower mass loss (13.8-18.8 wt.%) and contain >50 % less H2O than the CI chondrites. The 3-mu m feature is almost absent from spectra of Y-82162 and Y-980115 but the 11-mu m feature is intense. The CI-like chondrites experienced thermal metamorphism at temperatures >500 degrees C that initially caused dehydration and dehydroxylation of phyllosilicates before partial recrystallization back into anhydrous silicates. The surfaces of many C-type asteroids were probably heated through impact metamorphism and/or solar radiation, so thermally altered carbonaceous chondrites are likely good analogues for samples that will be returned by the Hayabusa-2 and OSIRIS-REx missions.