桂西天峨—凤山地区碳酸盐岩台地韧性剪切变形带

Deformation Belt of Ductile Shear from Carbonate Platform in the Tian'e-Fengshan Area,Western Guangxi

桂西天峨—凤山地区泥盆纪至二叠纪碳酸盐岩台地相地层均不同程度地发生过韧性剪切变形变质作用。在碳酸盐岩台地边缘,主要沿石炭系、二叠系的一定层位,形成了一套浅变质强变形、面型展布的钙质韧性剪切变形带,剪切变形带由强、弱变形亚带及两者之间过渡亚带组成。显微镜下观察发现:强变形带内变质变形岩石具糜棱结构,韧性剪切变形构造发育,属糜棱岩系列。研究表明,区内钙质韧性剪切变形带属浅层次逆冲型,主要是弧—陆碰撞挤压构造环境下变形分解作用的产物。

Different degrees of ductile shear deformation have occured from Devonian to Permian in Tian’e-Fengshan area,western Guangxi.On the edge of carbonate platform,especially along the specific lithohorizon from Carboniferous and Permian,a set of deformation belt of calcareous ductile shear formed,with features of low metamorphism,strong deformation and stratiform.The ductile shear deformation belts consist in strong,low and middle deformation belts.Under the microscope,it is discovered that the metamorphic and deformation rocks from the the ductile shear deformation belt are charactered by mylonitic texture,and belong to mylonitic series.The deformation belt of the calcareous ductile shear shows the feature of thrust and concluded to form by the mechanism of arc-continent collision in late period of Middle Triassic in Tian’e-Fengshan area.The discovery may provide new evidence for the analysis of the formation and development of the Youjiang basin in western Guangxi.