北祁连山东段大地构造演化与地洼构造

TECTONIC EVOLUTION OF THE EASTERN SEGMENT OF NORTHERN QILIAN MOUNTAIN AND ITS DIWA STRUCTURE

阐述了北祁连山东段的大地构造体制演化史;阐明地槽阶段的构造特点,划分出火山弧—弧前盆地—海洋三个古地理构造单元。概述了地台构造层及其反映的地壳活动特点。提出并论证自早三叠世进入地洼区体制,划分并阐述初动、激烈、余动期的特点;重点分析了地洼构造,划分出三种类型,指出它们的形成、发展和展布,主要受NWW和NE两组断裂的控制。

In this paper, the structural features of pre-geosyncline (Z-D), platform (D-P) and diwa (T-Q) stages of eastern segment of Northern Qilian Mountain and their evolution history are systematically discussed. The characteristics of geosynclinal structures are elucidated more comprehensively, and the paleogeosynclinal region is divided into three paleo_geographic_structural unites, namely volcanic arcs, frontalarc basins and oceanic crust. The distinctive features of the platform structural layer and the crustal movement at the plat_form stage mainly reflected by uplift are generally described. It is also proposed and proved that the studied region entered the diwa(geodepression) stage beginning from the Triassic. The division of the diwa stage into initial_mobility, maximum_mobility and residual_mobility periods and their characteristics are discussed in detail. It is then centered on the analysis of the structural setting of the diwa_basins in this area. The diwa-basins are classified into three categories and it is suggested that the formation, development and distribution of the diwa structures are essentially controlled by two sets of fractures trending NWW and NE respective_ly. The basic characteristics of diwa structures in the geodome series are summarized.