An Analysis Of Beijing Fangshan Complex Rock Mass Structures And Dynamics

Beijing Fangshan magmatic complex rock mass is located in a junction between the North China Plain and Taihang Mountains. It is formed in Yanshan orogenic belt of the north China landmass. Without encountering drastic tectonic transformation since late Mesozoic, the complex massif remains relatively stable.By observing the rock mass internal fabric and other factors including lava flows and surrounding temperature, we given quantitatively- semi-quantitative strained size and analyzed the dynamic mechanism of rock positioning mode.The area of the ellipse-shaped rock mass is about 56km2 with 9 km macro-axis from NW to SE,relation with surrounding rock for a simple intrusive contact. The contact area between the occurrence is so steep and inclined to surrounding rock. Within a certain range of surrounding rocks are subjected to contact metamorphism.As a typical complex rock mass, Fangshan magmatic rock mass is mainly the product of late Yanshanian magmatism twice formation, including the two parts of early small emplacement of quartz diorite rock mass and advanced large-scale emplacement of granitic diorite rock body.Analysis of Magmatic rocks formation and rebuilt the positioning model are important ingredients of the granitoids geologic structure study, so this research mainly focuses on the rock mass strain and internal fabric, other factors such as the surrounding rock temperature and the lava flows also taking into consideration.The Fangshan magmatites appears asymmetric arc strong ductile shear-zone in the northwestern rock mass margin. In this paper, we re-measure systematically petro-fabric in the Fangshan area,especially the northwest edge of the fabric(ductile shear structure and inclusion). Result shows slow structure occurrence in the south-east of rock mass,while the northwest occurrence more steep. Also,in northwestern, the strained condition either rock mass or ductile shear-zone inclusions is the biggest--the Maximum strain of 1:20.By observing the rock mass internal Strained fabric and other factors including lava flows and surrounding temperature, we analyzed the dynamic mechanism of rock positioning mode.