| 大别造山带东部假玄武玻璃的显微构造特征及其意义 |
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| 关键词:microstructure SEM deformation series pseudotachlite the eastern Dabie Mountain |
| 基金项目:国家自然科学基金项目(批准号:40172077);中国地质调查局国土资源大调查项目(编号:DKD2001009) |
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| Microstructure Characteristics of Pseudotachylites from the Eastern Dabieshan Orogenic Belt and Their Tectonic Implications |
| Recent field survey in eastern Dabie Mountain has revealed extensive existence of pseudotachylite. The pseudotachylite tends to occur in the NE-SW trending fracture zones or shear zones which parallel the Tan-Lu fault zone and cut the early-Cretaceous granites. Mylonitic bands are developed in some pseudotachylites. This paper mainly discusses the characteristics of microstructures between the pseudotachylites and their host rocks through observed mainly by optical microscope and SEM imaging. The microstructure characteristics of pseudotachylites and their respective wall rocks indicate that the pseudotachylites were formed mainly by ultracataclasis of wall rocks. Nevertheless, a small amount of corrosion borders along the margins of some porphyroid crystals of feldspar, plagioclase and pyrite from the SEM imaging of the sample Loc.1 suggest that there might have somewhat existed melt du-ring the pseudotachylite generation. The macro-mylonitic quartz bands have been proved to be the mylonitic foliation developed in early mylonitic breccias. The superimposition of microstructures shows the multi-stage development of the pseudotachylite-bearing fault zone and the pseudotachylite itself. In addition, the veins show features of progressive fracturing of the wall rocks interspersed with many rock fragments, which strongly suggests that antecedent cataclasis or pre-existing tectonic soften belt was a reworking and forming the pseudotachylite, so, pseudotachylites were formed in which they occurred. The deformation succession between the pseudotachylite and its wall rock generally exhibits the evolutionary process from ductile through ductile-brittle to brittle, which shows that the pseudotachylites were generally formed during the uplift of the orogenic belt instead of during the early subduction. |
| LIU Jian-min,DONG Shu-wen,ZHANG Jia-sheng,LIU Xiao-chun,CHEN Bo-lin.2005.Microstructure Characteristics of Pseudotachylites from the Eastern Dabieshan Orogenic Belt and Their Tectonic Implications[J].Acta Geoscientica Sinica,26(3):229-234. |
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