内蒙古大青山地区中生代造山运动及构造演化

MESOZOIC OROGENIC MOVEMENT AND TECTONIC EVOLUTION IN DAQINGSHAN REGION, INNER MONGOLIA

大青山地区是燕山—阴山板内造山带西段的重要组成部分 ,区内主体的构造格局和构造样式是由中生代地壳多期、多阶段构造变形的结果。印支期地壳以南北向挤压作用为主 ,是一次强烈褶皱造山运动 ,并伴随有强烈的岩浆活动。燕山早期阶段地壳仍然以挤压变形为主 ,形成了大青山逆冲推覆体系 ,同时控制了前缘断陷盆地沉积和演化。燕山中期由于区域构造背景的转变和重力作用 ,区域内发生了向南的伸展变形作用 ,形成了早白垩纪呼包盆地。燕山晚期地壳以挤压逆冲变形为主 ,不仅形成了楔冲式推覆构造 ,也使上白垩统与下白垩统为角度不整合接触。

Daqingshan is located in the western part of Yinshan-Yanshan intraplate orogenic belt, its tectonic outline and structural pattern were formed by crust polytectonic deformation in Mesozoic. Indosinian movement was a strong pressed folding orogenic movement in company with magma activity, which was dominated by N-S direction compression. Crust compresive deformation, dominating also in early Yanshan stage, formed Daqingshan thrust system and controlled the formation and development of foreland basin which occurred in front of Daqingshan thrust system. Crust deformation of middle Yanshan stage was extension, which was resulted by the changes of region tectonic stress field and gravity action, and formed early Cretaceous Baotou-Huhehaote extensional basin. Late Yanshan stage was compressive crust deformation which not only formed the wedge-type thrust structure but also caused upper Cretaceous Series unconformable contact with lower Cretaceous Series.