Multistage Deformation in the Northeastern Segment of the Jiangshao Fault (Suture) Belt: Constraints for the Relationship between the Yangtze Plate and the Cathaysia Old Land

Multistage deformation events have occurred in the northeastern Jiangshao Fault （Suture） Belt. The earliest two are ductile deformation events. The first is the ca. 820 Ma top-to-the-northwest ductile thrusting, which directly resulted from the collision between the Cathaysia Old Land and the Chencai Arc （？） during the Late Neoproterozoic, and the Jiangnan Orogenic Belt that formed as the ocean closed between the Yangtze Plate and the jointed Cathaysia Old Land and the Chencai Arc due to continuous compression. The second is the ductile left-lateral strike-slipping that occurred in the latest Early Paleozoic. Since the Jinning period, all deformation events represent the reactivation or inversion of intraplate structures due to the collisions between the North China and Yangtze plates during the Triassic and between the Philippine Sea and Eurasian plates during the Cenozoic. In the Triassic, brittle right-lateral strike-slipping and subsequent top-to-the south thrusting occurred along the whole northeastern Jiangshao Fault Zone because of the collision between the North China and Yangtze plates. In the Late Mesozoic, regional extension took place across southeastern China. In the Cenozoic, the collision between the Philippine Sea and Eurasian plates resulted in brittle thrusts along the whole Jiangnan Old land in the Miocene. The Jiangshao Fault Belt is a weak zone in the crust with long history, and its reactivation is one of important characteristics of the deformation in South China; however, late-stage deformation events did not occur beyond the Jiangnan Old Land and most of them are parallel to the strike of the Old Land, which is similar to the Cenozoic deformation in Central Asia. In addition, the Jiangnan old Land is not a collisional boundary between the Yangtze Plate and Cathaysia Old Land in the Triassic.

Structural Traces of Secondary Faults(Fractures) along the Main Faults and Their Reliability as Kinematic Indicators

Secondary/minor structures occurring along the main fault surfaces are important indicators for judging the kinematic characteristics of faults.However,many factors can lead to the formation of these structures,which results in the difficulty for rapid judgment and application in the fields.A series of secondary faults/fractures developed due to the movement of main faults are the most important and widespread phenomena in the scope of brittle deformation.The morphology of the main fault surfaces is various,and former researchers mainly discussed the structures on the main even fault surfaces. However,the fluctuation of fault surfaces is the intrinsic character of the faults,and the intersection between the main fault and secondary faults/fractures can produce a series of kinematic indicators on the main fault surfaces.Based on previous studies and our observations,i.e.the structural traces of the P,R,R',T and X shears/faults along the main faults,some indicators which are rarely reported previously,are described in the paper.Furthermore,their reliabilities are also discussed,and more practical and reliable criteria are brought forward.We suggest that the simple application of congruous and incongruous steps without knowing their exact origins should be abandoned in the fields,and several types of indicators along one fault surface should be checked with each other as much as possible.Meanwhile,the origins of some other arcuate indicators on the fault surfaces are also discussed,and new models are brought forward.