Libyan Desert Glass: New field and Fourier transform infrared data
Libyan Desert Glass: New field and Fourier transform infrared data
复制标题
利比亚沙漠玻璃：新场和傅立叶变换红外数据
DOI：
10.1111/maps.12223
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发表时间：
2013
影响因子：
2.2
通讯作者：
Edmond Diemer
中科院分区：
文献类型：
--
作者：
François Fröhlich;G. Poupeau;A. Badou;François;Bourdonnec;Yves Saquin;S. Dubernet;Jacques;Bardintzeff;Monette Véran;David C. Smith;Edmond Diemer
利比亚沙漠玻璃（LDG）是在埃及发现的一种独特的撞击玻璃，可能有2850 - 2940万年的历史。在大沙海主要LDG矿点以南约50公里处发现了一个新的LDG矿点。从傅里叶变换红外（FTIR）分析，LDG的分子结构的细化和LDG标本和其他纯石英玻璃（电熔石英，工业熔融石英，无定形生物硅），这是有关它们的结构差异之间的显着差异。这里观察到的不同玻璃之间的平均Si-O-Si角的轻微变化归因于它们的热历史。关于其他玻璃分析，LDG红外光谱参数指向一个较高的比率的不连续性和缺陷的四面体（SiO 4）网络。利用傅立叶变换红外光谱仪对LDG地质背景下的砂岩和石英岩进行了定量矿物学成分分析。白垩纪砂岩具有特定的成分（约90重量%石英，10%地开石），明显不同于古生代砂岩（约90重量%石英，但≥7%高岭石）。结果表明，含有LDG的红色粉砂主要由富含地开石的微石英组成，其粒度分布具有河湖沉积的特征，年龄可能为渐新世至中新世。目标岩石（很可能是石英砂）是来自Gilf Khebir高原的白垩纪砂岩在高能环境中沉积的风化（胶结微石英的损失）的结果。
Results are presented of new geological observations and laboratory analyses on Libyan Desert Glass (LDG), a unique kind of impact glass found in Egypt, probably 28.5–29.4 million years in age. A new LDG occurrence has been discovered some 50 km southward of the main LDG occurrences in the Great Sand Sea. From Fourier transform infrared (FTIR) analysis, the molecular structure of LDG is refined and significant differences are shown between LDG specimens and other pure silica glasses (fulgurite, industrial fused quartz, and amorphous biogenic silica) that are related to differences in their structures. The slight variations observed here for the mean Si‐O‐Si angle between the different glasses are attributed to their thermal histories. With regard to the other glasses analyzed, the LDG infrared spectral parameters point to a higher ratio of discontinuities and defects in the tetrahedral (SiO4) network. The quantitative mineralogical constitutions of sandstones and quartzites from the LDG geological setting were analyzed by FTIR. Cretaceous sandstones have a specific composition (about 90 wt% quartz, 10% dickite), clearly different from the Paleozoic ones (about 90 wt% quartz, but ≥7% kaolinite). It is shown that the reddish silts bearing the LDG are constituted mainly of microquartz enriched with dickite, whose particle size distribution is characteristic of fluvio‐lacustrine deposits, probably Oligocene to Miocene in age. The target rocks, most probably quartz sand, resulted from the weathering (loss of the cementing microquartz) of the Cretaceous sandstones from the Gilf Khebir Plateau with deposition in a high‐energy environment.