从江汉叠合盆地构造形变特征看华南与华北陆块的拼贴过程

构造解析表明,现今观察到的中扬子地区中部江汉叠合盆地主体构造格架面貌大体形成于印支 早燕山碰撞造山期;其中,主造山初期前陆盆地发育阶段,盆区东、西部构造形变差异明显,晚期经调整而渐趋平衡,由此显现华南与华北两大陆块在碰撞造山过程中可能先后经历了早期点状接触与陆间斜向俯冲和晚期线状接触与陆内俯冲两个发展阶段。晚燕山期以来,盆地裂陷阶段构造格架的分区发育与右行旋转特点,证明中扬子地区曾发生过双向伸展和构造旋转作用,暗示晚燕山 早喜马拉雅期华南与华北两大陆块可能处于逐渐焊合的过程,研究区总体处于造山后陆内应力场调整阶段。盆地坳陷期发育阶段山盆非耦合面貌及壳幔“立交桥”式结构特征展示晚喜马拉雅期以来叠合盆地南、北边缘造山带已进入去根与裂解过程中。

A DISCUSSION ON AMALGAMATION COURSE BETWEEN THE SOUTH CHINA AND NORTH CHINA BLOCKS:EVIDENCES FROM DEFORMATIONAL CHARACTERS IN THE JIANGHAN SUPERIMPOSED BASIN

The precisely structural analysis revealed that there were diversities of structural deformation between east and west parts of the Jianghan superimposed basin in the Middle Yangtze area during period of the foreland basin developing. The structural pattern mainly formed during the Indosinian and early Yanshanian orogenies. The South China(SCB)and North China(NCB)Blocks collided by two main orogenic stages: the early suturing being “spot-touching off” rotary collision and the later suturing being “line touching off” collision between the two continents. The deformational characteristics mentioned above demonstrated that the Middle Yangtze area once experienced a bilateral extension and rotation during rifting basin, which implicated a course that the SCB and NCB, in all likelihood, gradually sutured and amalgamated together. The region totally was situated in adjustable stage of field stress during post-orogeny. The physiognomy of basin-orogen decoupling and the architecture of “overfly” of crust-mantle during depression stage showed that the orogenic belts in both of the southern and northern margins of the Jianghan basin were derooting and collapsing since later Himalayan movement.