下扬子地区盆地的"四层楼"结构及其动力学机制

下扬子地区震旦纪以来经历了不同的大地构造与地球动力学背景 ,盆地演化相应地经历了震旦纪—中三叠世海盆→晚三叠世—中侏罗世沿江前陆盆地→晚侏罗世—早白垩世火山岩盆地→晚白垩世—早第三纪陆相伸展盆地。下扬子地区震旦纪—中三叠世海盆发育于伸展性被动大陆边缘。沿江前陆盆地形成于扬子与华北板块碰撞活动中的前陆变形带上。火山岩盆地出现于区域性走滑剪切和环太平洋岩浆弧背景下。库拉—太平洋板块高角度、高速正面向东亚大陆下的俯冲 ,造成了岩石圈上拱拉张 ,从而产生了晚白垩世—早第三纪的陆相伸展盆地。随着西太平洋边缘弧后盆地的出现及印度与欧亚板块的碰撞 ,中国东部遭受近东西向挤压 ,从而结束了下扬子地区的盆地演化历史。

"Four-story" structure of the basins in the Lower Yangtze region and their geodynamic setting

The Lower Yangtze region has experienced different tectonic and geodynamic setting since Sinian. Correspondingly, basins in the region evolved from the marine basin of Sinian to middle Triassic,the arround Yangtze foreland basin of late Triassic to middle Jurassic, volcanic basins of late Jurassic to early Cretaceous to extensional basins of late Cretaceous to Eogene. The marine basin of Sinian to middle Triassic in the region was developed on the passive, extensional continental margin. The around Yangtze foreland basin occurred in a foreland deformation belt caused by the collision between the Yangtze and North China plates. The volcanic basins were developed under the setting of regional strike slip and circum Pacific magma arc. Westward, low angle, high speed subduction of the Kula-Pacific plates resulted in lithosphere uprising and tension, leading to development of the extensional basins. With the presence of back arc basins on the western margin of the Pacific Basin as well as collision between the Indian and Eurasian plates, East China continent was subjected to E-W compression and the basin evolution was therefore ceased.