北祁连加里东造山带从挤压到伸展造山机制的转换

早古生代早期，北祁连造山带发生强烈的挤压变形作用，形成加里东期的俯冲－增生杂岩、高压变质岩，并使造山带岩石圈地壳加厚缩短。志留纪末期，加厚的造山带岩石圈由于垮塌作用及根部的拆沉作用，使造山带从挤压造山机制转换为伸展造山机制，并进入后造山伸展作用阶段，增厚的岩石圈开始减薄，发生不同层次的伸展作用，同时伴随花岗岩及Ａｎ∈变质岩的穹隆以及泥盆纪磨拉石盆地上叠盆地（Ｃ－Ｔ）的形成。石炭纪末，北祁连造山带岩石圈地壳已基本减薄到正常厚度。而现今的北祁连造山带的缩短和抬升则为喜马拉雅期再造山作用的产物

THE TRANSITION OF OROGENIC MECHANISM FROM COMPRESSION TO EXTENSION IN NORTHERN QILIAN OROGENIC BELT

During early period of early paleozoic era, as the result of substantial compression deformation, subduction accretionary complex and High pressure metamorphisum rocks formed and lithospheric crust thickened in Qilian orogenic belt. The transition from compression to extension developed during late silurian period, followed by late orogenic extension by collapse and delamination of thickened orogenic lithospheric crust. Development of different level extension led to thinning of thickened orogenic belt, accompanied by dome of granite and pre-cambrian metamorphic rocks and formation of superposed basins. During late carboniferous period northern Qilian orogenic belt returned to normal thickness. The present thickenning of Northern Qilian orogenic belt is the result of himalayan reorogency.