青藏高原日土地区构造单元划分、特征及演化

THE DIVISION AND THE FEATURE OF TECTONIC ELEMENT OF RITU AREA IN QINGHAI-XIZANG PLATEAU

西藏高原的构造单元及深断裂基本上汇聚在日土地区,是揭开青藏高原成因奥秘关键之地。笔者将该地区划分为6个亚一级和若干次级构造单元:昆仑海西、冈底斯早燕山两褶皱系和巴颜喀拉印支褶皱带具典型地槽性质,喀喇昆仑晚海西、喜马拉雅晚燕山两褶皱系和羌塘地块趋于准地台性质。各单元由活动转稳定过程、深断裂形成与封闭、岩浆活动等均具北老南新逐渐阶段性迁移特征;岩石圈固结有自北而南逐渐推移扩大趋势。巨大蛇绿岩带显示新生地槽的发展演化。

Ritu area assembles nearly all main tectonic elements and deep fractures and is a key area to disclpse the mystery of the forming of the Qinghai-Xizang Plateau. The author of this paper divides the area into six sub-first structural elements and into several secondary structural elements.Kunlun Hercynian fold belt,Gangdisi early yanshan fold belt and Bayankala fold belt are of the typical geosyncline characteristics. Kalakunlun late Hercynian fold belt, Himalaya late Yanshan fold belt and Qingtang massif seem to be the platform. The process of each fold belt from active belt to stable one, the forming of deep fracture and the erupting of volcanoes are of the characteristics of a gradual transition from the north toward the south. The consolidation of crust in Ritu area occurs in the way developing from the north toward the south. Great ophiolite belts offer some information, from which the history of geosynclines can be traced.