关键词: 喜马拉雅运动, 阿尔金断裂, 西域板块, 北祁连拗拉槽

Abstract: In the process of carrying out "West Development" policy,the tectonic outline of West China continent is very important for the exploration of oil and gas and other mineral resources.According to the recent researches,we have got three new understandings of West China tectonic:(1)The studies of laser probe ⁴⁰Ar/³⁹Ar dating in deformed rocks in Altyn fault suggest that the strike-slip event occurred or began at 97~89 Ma. These ages are consistent with the formation ages (102~85Ma) of the so-called "Western Tectonic Joint" in Himalayan.Sinistral strike-slip shearing has caused displacement to 350~400km along the Altyn fault zone,and tectonic zones and original basins are displaced from Late Cretaceous to Cenozoic. Therefore,the large-scale displacement must be taken into consideration when discussing the formation of the tectonic framework of Northwest China,including the reconstructions of the Precambrian blocks (including Rodinia super-continent),tectonic zones and orignal basins from Mesozoic to Early Tertiary.(2)The Tarim,Qaidam and Alxa block formed a Yangtze-type non-staleb craton in Paleozoic,called Western Craton,which is characterized by multiphase breaking at different locations, and together with the Yangtze-South China, Indosinian, Australian plates compose the Gondwana continent during Late Sinian-Early Paleozoic. The super-continent broken up and drifted later.The blocks are tectonically displaced and located during Late Paleozoic-Indosinian stage.They are further broken up and displaced during Himalayan stage and form separated basins (blocks).(3)The North Qilian Mountains is an Aulacogen formed due to the intra-continent breakup of the West China craton,instead of an oceanic basin,during Early Paleozoic.The west extension of the aulacogen goes to the Manjia' er-Awati depression at north central Tarim.The present framework and distribution are due to the sinistral displacement by the Altyn fault in Cenozoic.The Paleo-Qilian Mountain was formed during the closing of the aulacogen in Paleozoic.Planation was preceded during Paleozoic through Triassic and the mountain belt was transformed into cratonic basin.Due to extension during Jurassic to Early Tertiary,the North Qilian Mountains formed part of the original Hexi Corridor land basins.The formation of the present Qilian Mountains occurs from Pliocene to Early Pleistocene during the uprising of the Qinghai-Tibet Plateau.

Key words: Himalayan movement, Altyn Fault, Western Craton, North Qilian Aulacogen