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通过对桐柏-红安-大别造山带高压-超高压碰撞造山带详尽的几何学和运动学的剖析,厘定出高压-超高压变质岩经历了三期构造折返.它们分别是:(1)碰撞后折返:与造山带加厚岩石圈构造垮塌有关,主要表现为早白垩世NW-SE向的伸展,典型区域是北大别ENE-WSW向展布的变质核杂岩和WNW-ESE展布的桐柏山背形构造;其构造背景是伴随欧亚大陆东部伸展乃至华北克拉通破坏过程中,岩石圈尺度上大规模伸展作用对超高压变质造山带的改造.(2)同碰撞晚期折返:其构造展布区域主要为红安地区和中大别的经典超高压地区;构造几何形态同样表现为穹隆构造,沿穹隆的两翼发育有NNW-SSE的矿物拉伸线理和沿此线理发育的上部指向NNW的剪切变形;这期伸展事件发生的时间在230-205 Ma左右,对应的动力学机制可能是造山后加厚地壳的拆沉.(3)同碰撞早期折返:这是最早一期的伸展构造事件,主要记录在高压变质岩石单元及邻近的造山带前陆地区浅变质岩区系中;近南北向的折返使相关的构造板片发育有N-S向或NE-SW向的矿物拉伸线理;沿该方向的线理,岩板顶(北)部岩石变形的运动学为上部指向N或NE的剪切变形,而岩板底(南)部的剪切变形却表现为向S或SW的剪切;这一变形特征在武当山、桐柏山前陆、红安地体、大别山南部和宿松群、大别山东北缘的桐城等地区表现得最为明显;变形时间大致在250-235 Ma之间,其构造解释为伴随着大陆深俯冲过程中,俯冲到不同深度的变质岩发生同碰撞拆离折返.
Based on the detailed geometry and kinematics analysis of the Tongbai-Huanan-Dabie orogenic belt, the high-pressure-ultrahigh-pressure metamorphic rocks have undergone three stages of structural reentry: (1 ) Post-collision foldback: related to the thickening of lithosphere tectonic collapse in orogenic belt, mainly manifested as the extension of Early Cretaceous NW-SE direction. Typical areas are metamorphic core complexes distributed in the North Dabie-ENE-WSW and WNW-ESE The tectonic background of the Tongbai Mountain tectonic setting is the remodeling of the UHP metamorphic orogenic belt accompanied by large-scale extensional lithospheric scaling during the eastward extension of the Eurasia continent and even the destruction of the North China craton. (2) : Its structural tectonic distribution area is mainly the UHP region of the central part of Hongan area and that of the middle Dabie. The tectonic geometry also shows a dome structure, and the NNW-SSE mineral stretching line develops along the two wings of the dome and along this line The upper part of the development points to the shear deformation of NNW. The extensional events occur at about 230-205 Ma in this period, and the corresponding kinetic mechanism may be the detachment of thickened crust after orogeny. (3) Early reentry with collisions: The earliest stretch of structural events, It should be recorded in the high-pressure metamorphic rock units and the adjacent foreland metamorphic rocks in the orogenic belt. The reentrant north-south trending results in the mineralization of NS or NE-SW mineralogy along the tectonic plates. The direction of the line, the top of the rock (North) Department of rock deformation kinematics for the upper part of the N or NE shear deformation, and the rock bottom (South) of the shear deformation is manifested as S or SW shear The deformation features are most obvious in Wudang, Tongbai Mountain foreland, Hongan terrane, southern Dabie mountain and Susong group, Tongcheng northeast margin of Dabie mountain, etc. The deformation time is about 250-235 Ma, Its tectonic interpretation is that with the deep subduction in the continent, the metamorphic rocks subducted to different depths undergo the same collision detachment and reentry.