摘要
沿郯庐断裂带从大别山东麓经山东中部至辽北吉南的新宾—桦甸地区,暴露的早前寒武纪结晶岩石中存在着一系列北北东走向的大型韧性剪切带,其最大宽度达20km,走向断续延伸近2000km,它们分别在大别、鲁西和新宾地区形成了巨大的弧形牵引构造。剪切带中不同尺度组构要素的几何学,指示其中曾经发生了一致的大幅度左行位移;变形岩石的显微构造和矿物组合特征,说明这一韧性剪切带早期形成于低角闪岩相条件下,并且在抬升和冷却过程中经历了绿片岩相条件下的递进变形。山东中部晚元古代以后的沉积不整合于韧性剪切带及其变形岩石之上,中生代未期脆性的郯庐断裂系统追踪并改造了基底岩石中的韧性剪切带。
Investigations on fault structures and fault rocks in the exposed gneiss terrains of the Early Pre-cambrian have been carried out along the Tancheng-Lujiang fault zone from the east foot of Dabie mountain to Xinbing-Huadian area,the eastern part of the North China,including detailed tectonic-rock mappings at some areas of the terrains and microstructure analyses. It has been demonstrated that a large ductile shear belt had cut through the Archean North China craton before formation of the Tancheng-Lujiang fault zone. The shear belt is about 10 to 20 km wide and extends in NNE direction up to about 2 000 km long. Three huge drag arcs were formed along it at the eastern Dabie mountain,the eastern Taishan moutain and Xinbing area respectively. The deformation patterns and geometry of shape fabrics in the belt suggested that a large scale of displacement in sinistral sense had occurred along it. The microstructures and mineral assemblages in deformed rocks show that this ductile shear belt was composed of mylonitic gneisses formed early in a lower amphibolite facies conditions and mylonites formed late in a greenschist facies conditions, which represented the products of a continuous shearing during the crust uplift-related cooling. In the central Shandong Province, the ductile shear belts and their deformed rocks are covered unconformably by unmetamorphosed sediments after Tumen Group of the Late Proterozoic. This has restricted that the shear belts were formed and then exposed at the erosion surface at the Early to Middle Proterozoic. The brittle Tancheng-Lujiang fault zone was formed at the Mesozoic following the older ductile shear belts.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
1992年第4期363-372,T001,共11页
Earth Science-Journal of China University of Geosciences
基金
国家自然科学基金
关键词
郯庐
剪切带
断裂
性质
前寒武纪
Tancheng-Lujiang fault,ductile shear belt,Early Precambrian.
