The Regional Tectonic Characteristic And Their Evolution Of Metamorphic Rock Formation Kekesha Area In Dulan County, Qinghai

Tectonic evolvement of metamorphic rocks in Kekesha area in Dulan Qinghai is a multi—level, multi-phase development process. It's an important place for Research on development and evolution of the East Kunlun orogenic belt. There are many tectonic modes, and there deformations are complicated.On the basis of predecessors' investigation, writer had studied the tectonic deformation and evolvement characteristics in this area by the tectonic analytics and tectonics through wild investigation, survey and indoor analysis. There are some understandings as follows:1. Describe the metamorphic rocks deformation characteristics in the investigation area, including early tectonic permutation, structural superposition phenomenon, various small-scale folds(bedding recumbent folds, close isoclinal folds, rootless hook folds), tectonic len bodies, etc; large-scale folds, and ductile shear zone, brittle faults. Describe their macro-geometry, micro-geometry and kinematics characteristics, affirm their deep, media, shallow tectonic evolvement. Set up evolvement list.2.The characteristics of tectonic deformation in this area: portrait extrusion in early stage; then for the extension near the horizontal level of shear bedding; north west-south east slip away to the right line reverse phase; north east-west to the inverse of the left slip away.3.There are four tectonic actions in the evolvement history of the area: Meso-eoproterozoic ocean basin closure and tectonic thermal event in Jinningian; deformation stage under extand system in the latter half of the Neoproterozoic-Early Paleozoic, there were cracking event again to form islands pattern in ocean; shrinking system in Ordovician-Silurian, islands ocean closed and this area came to the intracontinental orogenic phase; the whole area came into intracontinental development stage after collision of Bayankela plot and East Kunlun in the middle and late Triassic. The continuous extrusion of stress lead to A-type subduction of East Kunlun lasting to Middle Jurassic (early Yanshanian). Qinghai-Tibet Plateau came into the stage of rapid ascend, which affect this area to form rift lake basin, alluvial fan and so on.