秦岭的大地构造演化

THE TECTONIC EVOLUTION OF THE QINLING MOUNTAIN BELT

一项中瑞合作研究成果表明,中国秦岭属碰撞型造山带。秦岭是在中生代造山运动早期由华北大陆板块与扬子大陆板块碰撞而成。原存于两大板块之间的古特提斯洋在泥盆纪时即已开始消减,仅部分洋壳残余于碰撞混杂岩中。

The Qinling Mountains can be divided into four tectonic units. They are from north to south: 1) Crystalline basement with its Sinian and Paleozoic cover of North China facies; 2) Me-tamorphic complex with ophiolitic blocks; 3) Flysch nappes; 4) Folded Paleozoic and Triassic strata of Yangtze facies. Using comparative tectonics, the Qinling Mountains are interpreted to be an orogenic belt of the collision type: The Qinling structures were formed mainly during the early Mesozoic Orogeny when the Yangtze Block came into collision with and thrust under North China. The rigid crystalline basement and its cover form an overthrust complex comparable to the Austroalpine Nappes. The metamorphic complex is comparable to the Penninic Nappes, including the ophiolite. melanges of the suture zone, the mobilized underthrust basement, and the metamorphosed sediments of the Paleotethys. The flysch nappes are equivalent to Prealpine Flysch. The foreland fold belt is characterized by thin-skinned deformation, and has a tectonic role equivalent to the Helvetic Nappes of the Alps. Mesozoic granites owe their origin to partial melting of the underthrust crust after the Triassic continental collision.