北京西山流动变形碳酸盐岩的微构造分析

本文提供一个可以与岩石力学变形试验相比较的碳酸盐岩天然流变实例。根据对变形岩石的构造微貌、应变特征、微构造相的系统分析,得出以下主要结论:（1）流动变形期的环境参数分别是:温度为250°～450℃C;压力为200—400MPa;差异应力为60—90MPa;在剪切带内可达110MPa;低应变速率(10^-13量级);（2）流变碳酸盐岩的典型组构是小圆环带的单斜对称型式。在剪切带内,可以无优选方位。岩石经受平面应变,略偏向拉伸应变,主压扁面与新生构造面理近于平行;（3）在中低温—中压,低应变速率的变形环境中,扩散作用是碳酸盐岩变形的重要机制之一。在强剪切带内,岩石进入第三蠕变阶段;（4）在褶叠层内部,应力、应变强度及应变速率的差异表明,分层差异剪切流动作为褶叠层的一种成因模型是可信的。

AN INVESTIGATION ON THE MICROSTRUCTURES WITHIN FLOW CARBONATES IN WEST-HILLS, BEIJING

Abstract This paper deals with the flow carbonate, which could be compared with the research in the deformation experiment of them. According to the systematic investigation on the anisotropy micrography and microstructure, strain, crystallographic texture and structural microfacies in flow carbonates, several conclusions are drawn as follows: (l)In the flow deformation stage, the controlling factors of deformation facies were: temperature 250-450; pressure 200 00MPa. differential stress 60?0MPa; or HOMPa in the shear zone: strain rate 10~ 1 3 (magnatitute grade). (2)Thc typical crystallographic texture in flow marble is monocline symmetry with a little circular, even inpreferential fabric in shear zone. The deformed rock had undergone plane strain and extension strain, and the pressure strain-lane is nearly parallel to the new structural plane (flow cleavage S1). (3)Under low-median temperature, median pressure and low strain rate, deffusion is one of the important mechanisms for the deformation of carbonates. Therefore, the deformation mechanisim could be operative in the third creep stage with the progressive shear zone. (4)It is creditable that the different shear flow in bedding rocks is regarded as an origin model of the folding layer, because there are clearly variations of the paleostress, strain, and strain rate in different parts of a folding layer.