江汉叠合盆地及邻区中生代以来盆山耦合数值模拟研究

江汉叠合盆地位于扬子地台中部,夹持于秦岭-大别及江南造山带中段之间。中生代以来,先后经历了北部陆陆碰撞、南部陆内挤压造山与断陷、裂陷成盆的演化历程,区域构造体制在中生代发生了重大转换,其中复合、联合了众多的地质现象;盆地历经的海盆、煤盆、盐盆、陆相广盆四个盆地世代详细记录有中国南北大陆联合及东北亚大陆构造体制转换的运动学过程,是认识欧亚大陆东部深层动力地质作用过程的关键地区之一。盆地沉积充填过程可简要概括为前陆、裂陷、坳陷三种基本样式。系统的盆山构造样式及运动学分析结果表明:叠合盆地前陆期发育于同碰撞-造山后作用阶段早期,断、坳陷期发育于造山后作用阶段晚期-非造山裂解阶段。本文运用大陆动力学数值模拟(FLAC软件)方法,从挤压和伸展两方面效验了山-盆演化分别受控于印支-早燕山期的华南与华北陆块的旋转碰撞造山,以及随后的晚燕山-喜山早期碰后陆内俯冲作用所产生的板片断离引起的地幔物质上升与对流作用,晚喜山期太平洋板块俯冲作用以及由此产生的地幔调整等三期动力学系统。为南方中小型叠合盆地动力学解析提供了一种新的思路与研究方法。

A NUMERICAL APPROACH OF COUPLING BETWEEN MESOZOIC SEDIMENTARY BASIN AND OROGENIC BELT IN JIANGHAN OVERLAIN BASIN AND ITS ADJACENT AREA

Jianghan overlain basin is located on the Middle Yangtze platform, between Qinling-Dabie and Jiangnan orogenic belts. It went through the continent-continent collision in the North and the extrusion orogeny in the South, occurs in fault-rift basin and rift basin in turn. Here the tectonic system has changed a lot, since it shows complex and united multitudinous geological phenomena and went through four stages of basin formation, i.e., stages of marine, coal, salt, and continent-wide basin formation since Mesozoic. The basin has detailedly recorded the kinetic processes that show the uniting of South China Continent and North China Continent and the conversion of the tectonic systems in Northeast Asia Continent. Jianghan overlain basin is also one of the pivotal areas where the deep dynamical and geological processes that occurred in the east Eurasia Continent were fully understood. On the basis of knowledge concerning the tectonic evolution of the basin, we reconstructed the basic stratigraphic framework, in which four supersequences are divided in all four basin-formation stages during Mesozoic and Cenozoic. The sedimentary filling sequences of the basin are generalized into three types, i.e., foreland, rifting and depression. Analysis of structural styles and movement modes of the basin and orogenic belt shows that the early foreland stage of Jianghan overlain basin grew with the collision orogenic stage or the early post-orogenic stage, the rift-fault and depression stage grew with the later post-orogenic stage and the orogen-splitting stage. Continent geodynamics numerical simulation (by using FLAC method) results show that the basin evolution was controlled by the Indosinian and early Yanshanian continent-continent rotation-type collision between the Southern and Northern China Continent Plates, by the late Yanshanian post-orogenic stress adjustment and slab breaking and mantle convection, and by the Himalayan interaction between Pacific Ocean plate and Eurasia Continent, in turn. In this paper a new idea and research method of kinetic solution for minitype and middletype overlain basins in South China were suggested.