A transmission electron microscope investigation of shock metamorphism in olivine of the Ilafegh 013 chondrite
A transmission electron microscope investigation of shock metamorphism in olivine of the Ilafegh 013 chondrite
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Ilafegh 013 球粒陨石橄榄石冲击变质作用的透射电子显微镜研究
DOI：
10.1111/j.1945-5100.1997.tb01268.x
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发表时间：
1997
影响因子：
2.2
通讯作者：
J. Doukhan
中科院分区：
文献类型：
--
作者：
Pascal Joreau;H. Leroux;J. Doukhan
摘要- Ilafegh 013是一种轻微风化的3型普通球粒陨石，它的不寻常之处在于它受到了高度的冲击。用透射电镜（TEM）对球粒中的橄榄石颗粒进行了详细的研究，以表征位错、断裂和再结晶织构。只有在（010）滑移面的c位错似乎被激波激活。在TEM中的裂缝比在光学显微镜的尺度上的裂缝更多。它们可分为两类：（a）开放性裂缝，注入熔融金属、硫化物，在某些情况下，注入含Ca、Al、Na和K的相。(b)平行于{130}面的非常直和窄的裂纹，没有注入材料，由两个位错族（伯格斯矢量a和c）组成的不完全松弛的亚晶界组成。两种类型的位错大致都是螺旋取向的（即，亚晶界具有明显的扭曲特征）。有人建议，他们形成的冲击，以放松周围的应力剪切断裂（骨折与位移的壁平行的断裂面）。再结晶发生在位错密度高的区域。由于没有检测到透晶玻璃，这表明再结晶是由于存储在变形晶体中的晶格缺陷的大的弹性能。
Abstract— Ilafegh 013 is a slightly weathered, type‐3 ordinary chondrite that is unusual in that it is highly shocked. Olivine grains in chondrules were studied in detail by transmission electron microscopy (TEM) to characterize the dislocations, fractures and recrystallization textures. Only c dislocations, in the (010) glide plane, seem to be activated by the shock wave. Fractures are more numerous in the TEM than at the scale of the optical microscope. They can be divided into two groups: (a) Open fractures with injections of molten metal, sulphide, and in some cases, phases containing Ca, Al, Na and K. (b) Very straight and narrow cracks parallel to {130} planes without injected material and consisting of imperfectly relaxed subgrain boundaries composed of two families of dislocations (Burgers vectors a and c). Both types of dislocations are roughly in screw orientation (i.e., the subgrain boundaries have a pronounced twist character). It is suggested that they formed during the shock in order to relax stresses around shear fractures (fractures with displacements of their walls parallel to the fracture plane). Recrystallization occurs in areas where the dislocation density is high. Since diaplectic glass was not detected, it is suggested that recrystallization resulted from the large elastic energy of the lattice defects stored in the deformed crystals.