Structural System And Tectonic Evolution Of Beiya Area

Beiya area locates in the western margin of the Yangtze plate and the southeastern margin of the Tibetan Plateau, it also at the intersection of Sanjiang arc basin system and the Yangtze plate. This paper took the structure system as the theme, the main tasks are as follows:Identify the property and distribution characteristics of major faults and folds in the study area; Identify the structural features and their combination characteristics. Analyze the distribution of alkali-rich porphyry and its relationship with deep faults; dividing tectonic stages based on the relationship of the faults, On the basis of the work above,analyze tectonic evolution and dynamic mechanism. By measuring tectonic sections which is continuous and can control the tectonic framework, collecting sufficient data on representative structure points and stratigraphics, drawing rose diagram of joint, point diagram, combined with remote sensing data, geophysical data, structural outline maps, regional geological maps as well as previous studies. conducting comprehensive study with the information above.The north-south trending structures has a dominate role in this area, mainly includes thrust faults, folds, normal faults and strike-slip faults. And the study area is divided into three tectonic units:Yangyushan thrust zone, Maanshan Strike slip fault zone and Songgui synclinorium zone.The geometric structure of the thrust fault includes benching structure and imbricate thrust fault-There is a sequence of conglomerate in the leading edge of thrust fault which locates near Dasongping.the size and the consists of conglomerate is complex and diverse.it is a kind of syntectonic sedimention, indicating that thrust fault and conglomerate could be developing at the same time -- late Triassic.Maanshan fractures exhibits tectonic superimposed characteristics, the early performance is thrust fault, the late performance is strike-slip fault or normal fauls due to the change of tectonic stress.In the study area, the distribution of alkali-rich porphyry is significantly controled by fractures, it mainly locates in the Maanshan fracture zone, the rocks and dikes distribute on both sides of Maanshan fault Maanshan fault and its derived secondary faults is the main fractures that controls the distribution of porphyry and ore deposite.Structural deformation is divided into five stages as follows:SN-trending thrust faults, SN-trending folds, SN-trending strike-slip faults and normal faults, EW-trending faults, NW and NE-trending fractures.