New progresses of geological mapping of tectonic melange zone in Yukahe area, the north margin of Qaidam Basin

In order to solve some key geological problems in studying tectonic melange zone in the north margin of Qaidam Basin, such as different genetic types of mafic-super mafic and high-ultrahigh pressure rock composition, subduction, collision-mechanism and formation process, we have carried out geological mapping work in Yukahe area, and got some progress and achievements. The contact relationship between the deep subduction geological body and native block was found out and it was characterized by ductile-brittle ductile shear zone in early contact and superposition thrust nappe in later contact. The eclogites were lenticular and layered in the deep subduction geological body, indicating that the protolith of eclogite was stratified and sheared before the peak metamorphism. The eclogites were in gneissic granite rock mass, which is in the form of eclipse body of the Yukahe Group. Internal deformation sequence and four deformation events were identified in this region. This deformation shows an extrusion character, and the extrusion happened at different stages. In addition, the authers also found out that the ultrabasic rock mass intruded into the deep subduction geological body.