太行-翼辽区NNW向构造体系——“华北系”的新厘定

THE NNW-TRENDING STRUCTURAL SYSTEM IN THE TAIHANG-HEBEL-LINONING AREA——REDEFINITION OF THE“NORTH CHINA SYSTEM”

本文在前人零星的遥感图象信息基础上,于“七、五”期间在太行—冀辽区(河北—辽宁)开展了野外实地考察和研究,发现等距相间的大量NNW向主干压性或压扭性构造带,以及彼此有成生联系的、力学性质不同的各向配套构造,如朝阳、滦河和紫荆关—怀安等三大构造带比较突出,它们共同显示了EWE—WSW或近EW向的构造应力场特征,由此将新第三纪以来,第四纪达到顶峰而形成的NNW向构造体系厘定为“华北系”。“华北系”的建立,目前在我国东部尚属首次。

The NNW--trending structural system of the Hexi structural system in westernChina has long been known, but it merely represents a product of the terminalMesozoic--early Cenozoic crustal movement. In recent years, the NNW--trending structu-ral features have been piecemeal reported in eastern China, but they are merelyremote--sensing image information which has not been subject to the field verificationof fault structures and the study of mechanical properties. Based on remote--sensing geologic surveys in the Yanshan area, the authors madea field study of the NNW--trending structural features when studying the Himalayanmovement in the Yanshan area in the period from 1985 to 1990. They discoveredthe Chaoyang, Luanhe and Zijinguan-Huaian compressive and compresso--shear faultswith about equal intervening space. These major NNW fault systems and theirrelevent structures of various trends and properties, together show the features of the ENE--WSW--or nearly E--W--trending structural stress field. Thus the NNW-trending structural system was formed in the Neogene and culminated in the Quater-nary. Principal NNW--trending structure of the system is mainly made up of compre-essive or compresso--shear fault structures, new uplifts of maintains, river drainagesystems and gentle anticlines. These structural features are typically and well develop-ed especially in North China, so the NNW--trending structural system is named the'North China System'. It was for the first time that the 'North China System' wasestablished or redefined in eastern China. Its formation or occurrence indicate thatthe stress field of the Neocathaysian structural system had essentially ended andtransformed in eastern China.