The Research Of Tectonic Characteristics And Evolution In Longmen Orogenic Belt

The research of intracontinent collision orogenic belt is an importantresearch area recently. It has important value for academic and application inresearch of tectonic movement and petroleum exploration in foreland basin.This paper took a system study in Longmen orogenic belt by fieldgeological observation and comprehensive study. The research shows thatinfrastructure controls superstructure, and ductile shear transits to brittlefracture in Longmen orogenic belt. Three belts have been recognized fromnorth to south ,that is root zoon, median belt and front strip. Root zoon isductile shearing and metamorphism. Median belt is developing imbricatefault and tectonic superimposing. In front strip, it develops blind fault andgentle fold. Ever since Devonian, Longmen orogen has experienced eighttimes structural events at least, the most strength one of which is duringYanshan movement. During Himalayan movement, it developed four timesstructural events. The lifting of Jiuding mountain at the present timereflected by GPS indicates that Longmen orogen inherits the character ofHimalayan movement. The dynamics of this intracontinental orogen is thatYangzi plate subducted into Chuanxi and Longmen areas with differentdetachment. The research also indicates that nappe structure extendedpiggyback propagation. The tectonic pattern in different epoch of geologichistory has been established in the paper.