Studies on the Lattice Distortion and Substructures of Shocked Lamellae in Naturally Shocked Quartz
Studies on the Lattice Distortion and Substructures of Shocked Lamellae in Naturally Shocked Quartz作者机构：Institute of Geochemistry Academia Sinica United States Geological Survey Mailstop 929 Reston Va 22092 United States of America
出 版 物：《Acta Geochimica》 (地球化学学报(英文版))
年 卷 期：1987年第6卷第1期
页 面：19-32页
学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学]
主 题：Studies on the Lattice Distortion and Substructures of Shocked Lamellae in Naturally Shocked Quartz
摘 要：One unshocked and 9 naturally shocked single quartz crystal grains with 1-6 sets of shock lamellaefrom the Ries, West Germany, and the Lake Lappajarvi, Finland, covering a range from unshocked quartzwith _disibledevent=1.544 to nearly completely glassy quartz with _disibledevent=1.461 have been used for X-ray precessionand Laue investigations. Four of the shocked grains have preliminarily been studied under a transmissionelectron microscope. It is found that quartz having No less than 1.539 shows intensive anisotropic cellexpansion and lattice disordering which gradually increase as No decreases. Shock-induced lattice distortionof quartz is clearly shown on both precession and Laue photographs. For the weakly shocked quartz (p200kb) slight to pronounced spreading of spots is observed. When the pressure reaches 200 kb, both concentricspreading of spots having long ‘tails and concentric rings (powder pattern) are revealed on the samephotograph, which means that besides a part of single crystal there also exist randomly oriented tiny‘fragments of quartz in this shocked quartz grain. As pressure increases from 230 to 315 kb, more and morecrystalline puases in the quartz grains have transformed from solid state into silica glass, and the concentricrings and the long ‘tails disappear and the spot spreading becomes slight again, but reflection intensitiesbecome much lower in comparison with those of weakly shocked quartz. TEM investigations show three kinds of substructures of shock lamellae. The glass contents of two ofthe four grains (73% and 84% respectively) were measured on TEM photographs with the help of an imageanalysis system. On the basis of above investigations a six-terminal-state model for the mechanism of deformation inshock metamorphosed quartz is presented.
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