西藏中部构造特征及印度板块仰冲问题

以负磁场为背景的航磁特征,揭示了基底是由浅变质的副变质岩组成的,属于柔性基底。 藏北断裂在磁场图上不明显。 雅鲁藏布江断裂是举世闻名的缝合线。反映雅鲁藏布江断裂的航磁异常带,具有强度大、连续性好和长度大的特点,为世界上罕见的大陆线性异常带。地面地质和各种地球物理资料查明断面是南倾的。 晚三迭世开始,印度板块在特提斯洋壳上向北仰冲,并导致特提斯在始新世的关闭。两大陆碰撞后,仰冲运动结束,代之以印度板块对欧亚板块南缘的推挤。

ON THE STRUCTURAL FEATURE IN THE CENTRAL PART OF XIZANG （TIBET） AND OBDUCTION OF THE INDIAN PLATE

The feature of the aeromagnetic field in the central part of Xizang, with negative values as its background, reveals the flexible nature of the basement, which is composed of low-grade parametamorphic rocks.The North Xizang fault is not clear in the aeromagnetic map.Yarlung Zangbo rift is a suture line between the colliding plates. The aeromagnetie anomalous zone over the rift, is characterised by high intensity, excellent continuity and great extention. Geological and various geophysical data indicate that the fault plane is inclined to the south.Since the beginning of the upper Triassic epoch, the Indian plate upthrusted to the north over the Tethys oceanic crust and led to the closure of the Tethys in Eocene epoch. After the collision of the two plates, the obduction movement was replaced by the pushment of the Indian plate towards the southern edge of the Eurasian plate.