摘要
雅鲁藏布江缝合带中的蛇绿岩在西藏南部不同地段,表现形式并不相同。通过对缝合带中段的构造特征及蛇绿岩组合特征的深入研究,认为印度板块的大陆地壳北缘具有特殊的波状弯曲的几何边界——东西两端为向北突出的犄角,构造结之间为向南突出的弧形边界。这种特殊的边界条件,在新特提斯洋俯冲碰撞过程中,新特提斯洋首先在突出结点处完成关闭,而发生南北大陆的碰撞;而位于结点之间的洋壳则以结点为中心分别逐渐向南凸的弧形中心扩展,发生结点之间洋壳的关闭和大陆的碰撞;但由于陆壳的刚性和结点的约束,不同长度的南北板块难以得到均衡的调整,致使结点之间南凸部分(仁布-拉孜一线)的新特提斯洋难以俯冲消减至北部欧亚大陆板块之下,而以未消失的新特提斯洋壳残留在这个特殊的位置,形成具有宽度巨大、原始结构有序、构造连续的蛇绿岩。
The ophiolite in the Yarlung Zangbo Suture Zone displays different forms with different areas in southern Tibet. Our detailed research on tectonic characteristics and the composite feature of ophiolite in the middle Suture Zone shows that the northern edge of the continental crust on the Indian plate has an overall wavy boundary with two nodes protruding respectively at the east and west of the zone and arc-shaped boundary in the south especially at the convergence point of two structures. The boundary conditions of this kind led to closure of the Neo-Tethys Ocean initially the two protruding nodes during the process of subduction and collision of the Neo-Tethys Ocean,resulting in the collision between southern and northern continents. The oceanic crust located between the two nodes spread southward to the arc-shape boundary from the nodes,giving rise to the closure among oceanic crusts and continental collision. Due to rigidity of the oceanic crust and constraint of the nodes,the southern and northern plates with various lengths could not be adjusted evenly. This could not lead to subduction and consumption of the Neo-Tethys Ocean at the arc-shape boundary （from Rinbung to Lhazê） beneath the northern Eurasian plate. Therefore,the remnant of the Neo-Tethys Ocean remains and forms a much wide ophiolite belt with continuous original structure.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2011年第1期56-65,共10页
Acta Geologica Sinica
关键词
雅鲁藏布江缝合带
蛇绿岩
成因模式
俯冲
碰撞
板块
Yarlung Zangbo suture zone
ophiolite
genetic model
subduction
collision
plate
