从地壳上地幔构造看洋陆转换作用  

Ocean—Continent Transition Process Reveled by Worldwide Comparison of Crust and Upper Mantle Structures

作　　者：杨文采[1] 宋海斌[2] 

机构地区：[1]大地构造与动力学国家重点实验室、中国地质科学院地质研究所,北京100037 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《地质论评》2014年第1期1-21,共21页Geological Review

基　　金：国家自然科学基金委员会和中国科学院“板块构造与大陆动力学”学科发展战略项目资助

摘　　要：根据近年来全球地壳上地幔探测的成果,分析了洋陆转换、地壳和岩石圈加厚的作用过程。洋陆转换作用可分为以下五个演化阶段:①同大洋扩张期的地壳增厚;②海沟发生与早期俯冲;③俯冲带成熟与沟弧盆体系形成;④俯冲带汇聚和位移;⑤陆—岛碰撞和陆壳连接。同大洋扩张期的地壳增厚作用指发生在被动大陆边缘的地质作用。包括沉积作用,岩浆底侵作用,下地壳和岩石圈地幔压裂,形成海沟等。海沟形成后陆缘转变为主动大陆边缘,大地构造机制转换为板块俯冲作用。成熟期的洋—陆转换作用特征是海盆扩张和板块俯冲造成的洋壳缩短取得平衡。弧后盆地和弧后边缘海的打开,表明俯冲带进入完全成熟的阶段。洋脊俯冲之后过成熟期的洋—陆转换作用,其特征是海盆逐渐缩小而且板块俯冲带汇聚。这里既有密集的俯冲带又有短期打开的边缘海岭;俯冲带不断位移,既可后撤也可前冲;俯冲板块经常发生断裂和拆沉。过成熟期的板块俯冲结果是边缘海微板块的萎缩。经过陆—岛碰撞,岛弧地壳增厚,与大陆板块连为一体,成为大陆内部的一个构造单元,即显生宙的"古洋—陆转换带"。Based on geophysical investigations of worldwide crust and upper mantle, this paper analyzes ocean--continent transition process and lithospheric thickening process. The ocean--continent transition process contains five stages： ① crustal thickening during co-expansion of an ocean, ② trench formation of and early subduction, ③ mature subduction and formation of trench--arc--basin belts, ④ convergence and migration of subduction zones, and ⑤ island--continent collision and connection to a continent. Geophysical profiles show that the crustal thickening during co-expansion occurs in passive continental margins, sedimentation, magma underplating and ultra-pressure hydraulic fracturing resulting in formation of trenches. After formation of trenches the passive continental margins become active, tectonic mechanics tends to subduction. In the mature subduction stage the expansion of ocean basins keeps compensation with the crustal shortening of the subduction, while opening of back-arc basins or marginal seas indicates the mature subduction stage. During the post-mature subduction stage, marginal sea micro-plates are narrowing and subduction zones are convergence and migrating. Crowded and short subduction zones with different subduction directions can cause local extension basins, they all mix together. Ascrustal thickening and gravity equilibrium go on, the arc belts would uplift and finally connecting to a island--continent collision, becoming a special unit of continental lithosphere, i.e. the phanerozoic continent zone. continent via eon ocean--

关 键 词：板块构造学 地壳上地幔探测 洋陆转换 地壳和岩石圈加厚 大陆增生 

分 类 号：P542.5[天文地球—构造地质学]