西藏南部同位素地质年龄的测定与喜马拉雅运动的分期

作者对1973—1975年中国科学院青藏高原综合科学考察队和1975年中国登山队科考分队地质组,在西藏南部和珠穆朗玛峰（以下简称珠峰）地区采集的部分同位素地质年龄样品,经镜下鉴定,选择适宜者用钾氩法做了同位素地质年龄的测定,从而对本区广泛出露的岩浆岩和变质岩的时空分布特征加深了认识。在工作中钾是用火焰光度法测定的。放射成因氩的含量大部分是用体积法测定,小部分用以Ar38为稀释剂的稀释法测定。

K-Ar DATING AND DIVISION OF THE HIMALAYAN MOVEMENT IN SOUTHERN XIZANG

Samples collected from Southern Xizang were determined by K-Ar method. Basing on these isotopic data and making use of geological materials available we have found that the northward drifting of the Indian Plate is a continuous process during Late Cretaceous to Pleistocene in this region. The spatial distribution of dating data also shows that the Indian Plate and the Eurasian Plate moved against one another.As to the crustal movements involved in the tectonic history and the recent tectonic framework laid down during the Mesozoic in this region, we are inclined to divide them into four stages: (1) the Late Yanshan movement of Late Cretaceous, 119.3-64.5 m.y.; (2) the episode Ⅰ of Himalayan movement in Eocene, 54.9-42.0 m.y.; (3) the episode Ⅱ of Himalayan movement in Oligocene, 35.6-26.8 m.y. and (4) the episode Ⅲof Himalayan movement from Miocene to Pliocene, 24.7-6.4 m.y.