摘要
根据近年来全球地壳上地幔探测的成果,分析了大陆碰撞造山作用过程。在大地构造物理学中,演化重建的基础为地壳上地幔探测结果和宏观物理学定理,方法为岩石圈结构模型的解构。大陆碰撞使洋陆转换带岩石圈正式拼入大陆板块,造成大陆的增生。阿尔卑斯—喜马拉雅碰撞造山带在碰撞前陆缘广泛发育有洋—陆转换带,这种碰撞称为裙边碰撞。由于比较松软的洋陆转换带岩石圈夹在中间,裙边碰撞时不发生典型的刚性碰撞和反弹,碰撞产物中常见蛇绿岩套及泥砾混杂堆积,少见超高压变质岩片的折返。大别—苏鲁碰撞造山带在碰撞前洋—陆转换带不发育,这种碰撞称为裸碰撞。裸碰撞属于刚性碰撞,碰撞时发生反弹,碰撞产物中少见蛇绿岩套及泥砾混杂堆积,常见超高压变质岩片的折返。裸碰撞后的反弹为超高压变质岩片的折返创造了条件。裙边碰撞和裸碰撞的作用过程都可分为四期,第一期为碰撞前期,第四都为后造山期。裙边碰撞和裸碰撞的不同在于,第二期主碰撞期裙边碰撞冲撞大陆板块没有明显反弹,第三期陆—陆俯冲期超高压变质岩片折返不明显。造山后期是碰撞造山过程逐渐停息期,即两大陆板块间的应力从挤压转化为拉张的阶段。这时两大陆板块之间有了共同的一个旋转极,但是碰撞造山诱发的岩石圈拆离和变形仍在进行,碰撞带岩石圈成为大陆内部热流会聚和岩浆活动的优选通道,诱发强烈的岩浆活动。
Based on geophysical lithospheric investigations worldwide,this paper analyzes the continental collision orogenic process. The geophysical lithospheric investigation data as well as physical laws build the foundation for reconstruction of evolution and the deconstruction method for interpretation of deep reflection profiles. Continental collision results in accretion of continents from the ocean—continent transition( OCT) zones. Owing to widely development of the OCT zones,the Alps—Xizang( Tibet) collision orogenic belt belongs to the so-called skirt-plate collision type,which does not act like elastic collision with no rebounding effects. This type collision usually shows ophiolite but few ultrahigh metamorphic belts on the surface. On the other hand,owing to rarely development of the OCT zones,the Dabie—Sulu collision orogenic belt belongs to the so-called nude-plate collision type,which acts like elastic collision with rebounding effects. This type collision usually shows ultrahigh pressure metamorphic belts but few ophiolite on the surface. The rebound created conditions for exhumation of the ultrahigh pressure metamorphic belts from deep mantle. Both the skirt-plate and nude-plate collisions contains mainly four collision stages:( 1) pre-collision stage involving ocean subduction and closing,( 2) pre-collision stage,( 3) latecollision stage or continental-to-continental subduction stage,and( 4) post-orogeny stage. At the pre-collision stage,the skirt-plate collision do not rebound but the nude-plate collision does. At the late-collision stage,the skirt-plate collision does not show the exhumation of the ultrahigh pressure metamorphic belts but the nude-plate collision does. The post-orogeny stage means gradually stopping the orogeny process,lithospheric stress between continents in collision transfers to extension state from compressional state,resulting the same rotational pore between the two continents. However,lithospheric deformation and detachment can still occur,and convergence of deep heat fluids and magma intrusions would prefer play important roles in the week lithosphere along the collision belts.