中国东部及邻区早白垩世裂陷盆地构造演化阶段

Tectonic evolution stages of the Early Cretaceous rift basins inEastern China and adjacent areas and their geodynamic background

早白垩世是中国东部及邻区强烈的伸展裂陷和岩石圈减薄时期。根据裂陷盆地几何形态特征和展布型式 ,将早白垩世裂陷盆地分为泛裂陷型 (燕山—松辽断陷盆地群、蒙古断陷盆地群等 )、狭窄型 (沂沭裂谷系、伊兰—伊通裂谷带 )和菱形状型 (胶莱盆地、三江盆地、鸡西盆地等 ) 3种类型。通过综合分析和对比不同类型裂陷盆地沉积序列和构造演化历史 ,结合郯庐断裂带和秦岭—大别造山带白垩纪构造演化历史的研究成果 ,区分了中国东部早白垩世 2个显著不同的引张裂陷阶段和一个构造挤压反转阶段。早白垩世早期引张裂陷阶段 ( 1 4 0～ 1 2 0Ma)形成了宽广展布的燕山—松辽断陷盆地系和蒙古断陷盆地系 ,沿郯庐断裂带发生右旋走滑活动 ,控制了断裂带西侧南华北伸展走滑盆地和东侧胶莱、三江等和沿敦—密断裂带走滑拉分盆地的发育 ;早白垩世中期引张裂陷阶段 ( 1 2 0～ 1 0 0Ma) ,沿郯庐断裂带中、北段发生裂谷作用 ,形成沂沭裂谷系和伊兰—伊通裂谷带 ;早白垩世晚期 ( 1 0 0～ 90Ma)在区域NW SE向挤压应力场作用下 ,所有早白垩世裂陷盆地发生不同程度的构造反转 ,沿郯庐断裂发生强烈的左旋走滑运动。最后指出 ,太平洋古板块向东亚大陆边缘俯冲诱发的大陆岩石圈底侵作用、拆沉作用、地幔底辟和对流 。

The Early Cretaceous was a period of intensive intracontinental rifting, crustal stretching and lithospheric thinning in Eastern China and adjacent areas. According to the geometric characteristics and distribution patterns, the Early Cretaceous rift basins can be grouped into three types. They are the wide-developed rift basins such as the Yanshan-Songliao rift basin system and the Xing-Meng rift basin system, which developed in NE China and in east Mongolia; the narrow-and-elongate shaped rift basins like the Yi-Shu rift system and the Yilan-Yitong rift zone, which developed along the Tan-Lu fault zone; and the rhomboid-shaped rift basins such as the Jiaolai basin, the Sanjiang basin, the Jixi basin etc., which developed along the two sides of the Tan-Lu and Mishan-Dunhua fault zones. By comparing the sedimentary sequences and tectonic evolution history among different types of these rift basins, and taking into account the study results of tectonic evolution history of the Tan-Lu fault zone and the Dabie Shan orogenic belt, this paper distinguishes two distinct rifting stages and one tectonic inversion of rift basins during the Early Cretaceous. An early rifting stage during the period of 140～120 Ma was characterized by the formation of wide distributed rift basin systems in NE China and in east Mongolia and by the initiation of transtensional strike-slip basins along the two sides of the Tan-Lu fault zone. A middle rift stage during the period of 120～100 Ma was marked by the formation of the Yi-Shu rift system and of the Yilan-Yitong rift zone along the middle and northern segments of the Tan-Lu fault zone. A late stage during the period of 100～90 Ma was dominated by tectonic inversion of the Early Cretaceous rift basins imposed by NW-SE compression; it was during this stage that the Tan-Lu fault zone slipped left-laterally. It is pointed out that the underplating, delamination and back-arc mantle convection of the continental lithosphere, induced by westward subduction of the Paleo-Pacific Plate beneath the Asia continent, and together with the eastward extrusion of continental fragments imposed by block collision in West China, jointly controlled the processes of the Early Cretaceous rift basin formation and fault kinematics in Eastern China and adjacent region.