青藏高原的形成和演化机制

青藏高原是地球上最高大和最雄伟的年青隆起区。对于它的形成和演化机制,一直是国内外地质和地球物理学者注意的问题之一。 近十年来,人们认为青藏高原的形成是由于相距千里之遥的印度板块向北漂移并与欧亚板块碰撞的结果。然而,根据作者对喀喇昆仑和喜马拉雅等地的野外考察及其深部地球物理资料的研究,提出青藏高原原来是一个统一的前震旦纪陆壳区,后经震旦纪以来多次的拉开和挤压碰撞而形成的新观点。这种拉开和挤压的运动方式,是深部鳗隆和慢拗的分异作用引起的。

PRELIMINARY DISCUSSION ON MECHANISM OF THE GENERATION AND EVOLUTION OF THE QINGHAI-TIBETAN PLATEAU

Based on the analysis of a large amount of geological data collected, the subdivision of tectonic units in Qinhai-Tibet and adjacent area have been made in this paper. Therefore, a new idea is presented that Qinghai-Tibetan plateau might originally be a united Presinian continental tectonic domain and has been formed by subsequent multiple extension, compression and collision since Sinian period.In this paper more details are discussed on three tectonic divergence-convergence belt: Tongtian He, Bangong Co-Siling Co, Indus-Yarlung Zangbo, which have a unique tectonic feature demonstrating in strong tectonic deformation, well developed folds and faults. Moreover, there are remains of mature or inmature oceanic crusts.These features show that the above-mentioned three belts had experienced the stage of development of epicontinental oceanic rift or initial epicontinental oceanic rift, and then were separately subjected to compression of Indosinian movement, Yanshanian movement and Early Himalayan movement and eventurely led to the closing of these rifts.Correspondingly, from North to South the Indosinian, Yanshaian and Early Himalayan paleo-oceanic rift belts were subsequently occurred.These paleo-oceanic rift belts were completed by two styles of crustal movement: Ex-tention causing the subsidence and transformed continental crust into inital oceanic crust or oceanic crust; compression caused the uplift and transformed oceanic crust into continental erogenic zonetectonic divergence-convergence belt. Through studies on both superficial and deep structures in worldwide young tectonic regions make us to be able to consider that the above mentioned multiple extensions and compressions of the continental crust are related to the tectonic differenciation of the upper mantle.The uplifting of the upper mantle caused the extension of the crust, whereas the depression of the upper mantle led to compression of the crust. To our knowledge, that is the most important mechanism of the generation and evolution of the Qinghai-Tibetan plateau.