印度支那地块第三纪构造滑移与青藏高原岩石圈构造演化

Tertiary Squeeze-out of the Indo-China Block and Lithospheric Evolution of the Qinghai-Tibetan Plateau

印度支那地块于早第三纪至中新世发生大规模地向东南方向走滑,同时伴随着15°顺时针旋转。青藏高原及邻区晚自垩世以来的古地磁古构造及地质年代学研究新成果,说明青藏高原岩石圈的构造演化过程,即古新世初印度板块与欧亚大陆的南缘拉萨地块碰撞,至49 Ma左右印度与拉萨地块发生全面拼合,随着印度板块进一步向北挤压,从碰撞期至16 Ma,印度支那地块沿红河大型走滑断裂发生侧向滑移;印度与“欧亚大陆”之间的构造缩短通过岩右圈板块沿着大型走滑断裂系的挤出以及板块间的消减得到调整。青藏高原大规模的岩石圈构造缩短很可能始于中新世27 Ma左右沿着早期陆块间的接合带发生。一些事实还说明青藏高原的总体隆起很可能是通过10 Ma前后和3 Ma以后多期非均匀隆升形成的。

Indochina has suffered a relative southward motion of 8°± 4°along the Red River fault zones and approximately 14°±7°of clockwise rotation for the Indo-china block relative to the Chinese blocks. These results, according to the above study combined with the recent progress in the geological and geochronological studies of the Red River fault, and the Qinghai-Tibetan plateau, it is implied that the process of multi-stage lithospheric evolution of the plateau, i. e. the collision between India and Eurasia occurred at the beginning of the early Palaeocene and that the completely suturing took place around 49 Ma between the two blocks. The continental shortening between India and the deformation of the plateau (or the continental shortening between India and Siberia) involved both crustal thickening and lateral squeeze-out of blocks along the major strike-slip zones. The penetration of India into Eurasia between 49 Ma and 16 Ma resulted in the slip of Indo-china southeasterly along the Red River fault, which coincided with seafloor spreading in South China Sea and continental shortening along the block boundaries. Some geochronological results suggest the uplift of the plateau resulted from multi-stage inhomogeneous uplifts around 10 Ma B.P. and after 3 Ma.