青藏高原隆升的历史背景和机因

青藏高原自中、上新世大幅度的隆升、形成，是亚洲大陆壳体演化-运动历史中，与地洼构造活动有直接关系的重大事件之一。对青藏高原形成的原因，运用历史一动力大地构造学的研究方法，从多方面的资料综合分析，可以得到较为合理的解释。根据上地壳结构、历史背景、占植物区、地热活动状态等资料，对隆升运动的物质基础、物理因素、内动力和外动力因素；及其对壳体演化一运动史的制约等的综合分析，表明青藏高原的隆升运动发生于亚洲大陆接纳印度外来壳体的过程完结之后，是在另一次和另一种地壳运动中出现的。从力学上说是在碰撞力及后继挤压力已衰退，又经青藏统一古地台形成、以垂向运动占主导的稳定区阶段的间断之后，再度转入活动区阶段，由于多方面的挤压力才开始发生的，是属于另一个壳体演化阶段和另一个应力场的产物。在造山带的性质上，隆升事件是在印度壳体与中亚壳体汇聚接合已经完成，印度大陆已成为亚洲大陆的一部分，并且碰撞造山力及其后继厂力都已为地台型地壳运动所代替之后，才由于大陆内部的地洼型造山作用所致的。

MECHANISM AND HISTORICAL BACKGROUND OF THE UPLIFT OF THE QINHAI-XIZANG (TIBET) PLATEAU

The uplift of the Qinghai-Xizang (Tibet) Plateau happened in a different crustal movements and different time from those of the collision of Asia continent with the allochthonous India crustobody, and the uplift occurred very long after the finish of the collision. In fact, there are no directly causationic relationships in time and dynamics, as well as in crustobody movement nature between the uplift and collision. According its temporal evolution, the uplift happened in another active stage of the mantle creep flow after the active stage resultingin the collision and the Interruption of the 140 Mals quiet stage--particularly notlceably afterthis interruption of quiet stage - resulting in the universal Qinghai-Xizang (Tibet) ancientplatform. It was the production in another cycle of the mantle creep-flow active-quiet progression. On the basis of the dynamic analysis, the uplift resulted from the multiple compressing stresses in the reactivation stage after weakening of the colliding stress and the following compressing stress, and after the interruption of the stable stage dominating the vertical movements and represented by fomation of the universal Qinghai-Xizang (Tibet) cient platform. It was the production of another stress field existing in another crustobody evolution stage and growth age. In the light of the nature of the orogeny, the uplift was caused by the intracontinental diwa (geodepression)-type orogeny after converging connection of the Central Asia Crustobody and the India Crustobody which immediately later became a part of the Asia continent, and hence after the substitution for the colliding stress and the following compressing stress by the platform-type crustal movements.Because of the big temporal difference between the uplift and collision events, the socalled double-crust hypothesis of the Qinghai-Xizang (Tibet) Plateau may not be realistic.The collision began in Qinghai-Xizang (Tibet) region before or at early Permain when theQinghai-Xizang (Tibet) ancient platform and hence the paleoplanation surface, the morphological foundation of the plaleau, even were not in their embryonic forms, so the uplift of theplateau did not result from the subduction of the India crust at all. Normally it is inferredthat since the allochthonous india crust underthrusted northward before or at early Permain,hence immediately later the Qinghai-Xizang (Tibet) region should be elevated successivelyfrom South to north during Permian to early Mesozoic, but actually the Qinghai--Xizang (Tibet) region has risen more of less uniformly almost in the same period from Miocene, morethan 200 Ma years later than the beginning of the collision. On the other hand, because ofthe high heat flow, even if india crust exists under the Qinghai--Xizang (Tibet) region atdepth more than 30 km, it may change into plastic and even fused (see details from the abovementioned discussion) and may be unable to go on underthrusting northward. Moreover, noevidence has been found for the existence of the India crust under the plateau yet. Thereforesome Interfaces, inferred by geophysical materials in local areas, are reasonably consideredto be the evidence for nappes or decollement surfaces rather than for doubleWecrust.In terms of the mentioned above the mechanism of the Qinghai--Xizang (Tibet) Plateauneeds to be comprehensively analysed by thinking about multiple factors, especially bystudying the evolutionwmovements history of the related crustobodies and using the integrative research method of historic-dynamic geotectonics. So it can not be perfectly explainedsimply by the exogenetic action or by using the simple collision model, even the double--crusthypothesis.