辽东鞍山齐大山韧性剪切带运动学解析及形成机制
发布时间：2018-11-23 16:13
【摘要】：关于太古宙早期地壳演化构造机制的争论已经持续了数十年,其焦点主要集中于水平构造还是垂向构造两大经典构造模式的探讨.对于早期地壳构造演化方面的研究,将会有助于我们更好地理解早前寒武纪的地球动力学机制.本文对华北克拉通东北部鞍山地区花岗-绿岩带内齐大山韧性剪切带的构造变形特征进行了详细的解析,揭示了该区新太古代垂向构造作用样式.研究结果表明,齐大山韧性剪切带内花岗质岩石长英质矿物塑性拉长特征明显,条带状构造发育,面理向NWW方向陡倾,不对称组构特征和矿物拉伸线理产状指示向NWW的陡倾正滑移剪切作用.变形岩石中的长英质矿物均发育中低温显微变形特征,石英C轴电子背散射衍射(EBSD)组构分析揭示石英以菱面a和底面a滑移系为主,岩石经历了中低温非共轴变形.根据矿物的变形行为以及石英的结晶优选方位推测变形温度约为400~500℃,岩石变形特征以位错蠕变为主.有限应变分析结果表明,靠近铁矿带方向,构造岩类型由L=S构造岩过渡为LS构造岩,岩石应变强度呈明显增强趋势.运动学涡度测量结果显示齐大山韧性剪切带内大多数岩石样品的Wk值大于0.75,岩石形成于以简单剪切作用为主的一般剪切作用.对比花岗-绿岩带西侧的白家坟韧性剪切带,显示二者均具有相向的陡倾正滑移运动学特征,表明新太古代时期鞍山地区地壳构造演化模式以垂向构造作用为主.
[Abstract]:The debate on the tectonic mechanism of the early Archean crustal evolution has been going on for decades with the focus mainly on the discussion of the two classical tectonic models of horizontal or vertical tectonics. The study of early crustal tectonic evolution will help us to better understand the geodynamic mechanism of the early Precambrian. In this paper, the tectonic deformation characteristics of Qidashan ductile shear zone in the granite-greenstone belt in the Anshan area, northeast of North China Craton, are analyzed in detail, and the new Archean vertical tectonic patterns in this area are revealed. The results show that the feldspar minerals of granitic rocks in Qidashan ductile shear zone have obvious plastic elongation characteristics, strip-like structures are developed, and the plane is steeply inclined towards NWW. Asymmetric fabric characteristics and mineral tensile lineage indicate steep-dip normal slip shear to NWW. All the feldspathic minerals in the deformed rocks are microdeformed at moderate and low temperatures. The (EBSD) fabric analysis of quartz C-axis electron backscattering diffraction reveals that the quartz is dominated by rhombohedral a and bottom a slip systems, and the rocks have undergone moderate and low temperature non-coaxial deformation. According to the deformation behavior of minerals and the optimum orientation of quartz crystallization, the deformation temperature is about 400 ~ 500 鈩，
本文编号：2352027
[Abstract]:The debate on the tectonic mechanism of the early Archean crustal evolution has been going on for decades with the focus mainly on the discussion of the two classical tectonic models of horizontal or vertical tectonics. The study of early crustal tectonic evolution will help us to better understand the geodynamic mechanism of the early Precambrian. In this paper, the tectonic deformation characteristics of Qidashan ductile shear zone in the granite-greenstone belt in the Anshan area, northeast of North China Craton, are analyzed in detail, and the new Archean vertical tectonic patterns in this area are revealed. The results show that the feldspar minerals of granitic rocks in Qidashan ductile shear zone have obvious plastic elongation characteristics, strip-like structures are developed, and the plane is steeply inclined towards NWW. Asymmetric fabric characteristics and mineral tensile lineage indicate steep-dip normal slip shear to NWW. All the feldspathic minerals in the deformed rocks are microdeformed at moderate and low temperatures. The (EBSD) fabric analysis of quartz C-axis electron backscattering diffraction reveals that the quartz is dominated by rhombohedral a and bottom a slip systems, and the rocks have undergone moderate and low temperature non-coaxial deformation. According to the deformation behavior of minerals and the optimum orientation of quartz crystallization, the deformation temperature is about 400 ~ 500 鈩，
本文编号：2352027
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