Research Of Structural Characteristics And Deformation Mechanism In The Xuhuai Region

Xuhuai Arcuate Structure is located in the southeastern margin of the North China Craton and western Sulu orogenic belt, and the Tanlu fault belt is connected to the Yangtze Craton on its eastern margin. In the research area, the trajectory of the main folds and faults in a plane showed a series of arc which protrude towards NWW. On the basis of systematically collecting and summarizing previous research results, and through detailed field geological investigation, Xuhuai Arcuate Structures is demonstrated as "Sukodu-style" tectonic deformation pattern, as three sections are divided from South to North, which are the north zone, middle zone and south zone; frontal zone, middle zone and back zone from west to east, and lower structural layer, middle structural layer and upper structural layer vertically. According to the inversion on the north and middle sections fault stress field of Xuhuai Arcuate Structure, it is formed under regional compression settings, the direction of the principle stress is SE-NW, besides, and normal fault was developed under latter extension settings, the direction of tension stress field is also SE-NW. Combined the sedimentary environment of situ formation and the regional tectonic settings, extrusion-gravity gliding dynamic mechanism is brought up as to explain the formation of Xuhuai Arcuate Structure. Numerical modeling study on Xuhuai Arcuate Structure sufficient verified that the tectonic setting of the arc formation is from SE extrusion force. It affirmed that the arcuate structure is formed under the extrusion-gravitational detachment mechanism. In this dissertation, boundary buried fault of the north and south side has been simulated which showed the restriction of the arcuate structure’s formation.Based on the field geological investigation, inversion of the fault stress field, the numerical simulation, and comprehensive analysis on unconformity events among stratum and ages of the exposed rock mass, the evolution process of Xuhuai arcuate structure has been summarized, T2-K1 are the principal-stage deformation is proposed and the evolution of the two stages of which established arcuate structure’s primary profile. During K1-E1, under the settings of regional extension, the existed thrust fault in the study area repeated becoming stretching normal slip fault, and graben basin in the east has developed. Since Neogene period, regional thrust-compression has slight influences on Xuhuai arcuate structure, tectonic deformation is feeble. Therefore, the deformation of Xuhuai arcuate structure is originated due to the continent-continent collision of South China Craton, which demonstrated that early eastern China has under the control of Palo Tethys tectonic convert to circum-Pacific tectonic of the north and south plate convergences.