柴达木盆地北缘鱼卡地区构造混杂岩带解剖填图新进展

针对柴达木盆地北缘构造混杂岩带中不同成因类型镁铁质—超镁铁质和高压—超高压岩的组成、俯冲-碰撞-折返机制及形成演化过程等关键地质问题,在柴北缘鱼卡地区开展了解剖地质填图工作,取得了系列新认识: 查明了深俯冲地质体与原地岩块的接触关系,表现为早期韧性—脆韧性剪切带接触,后期叠加逆冲推覆; 查明了深俯冲地质体中榴辉岩主要呈透镜状、似层状产出,表明榴辉岩原岩在峰期变质之前就发生了分层剪切; 查明了片麻状花岗岩体内部榴辉岩的产出特征,榴辉岩以鱼卡岩群残蚀体产出于片麻状花岗岩体中; 厘定了深俯冲地质体内部变形序列,识别出4期构造变形组合,表现为挤压型变形,指示本区经历了多期挤压汇聚作用; 明确了超基性岩体的就位环境,与深俯冲地质体为侵入接触关系。

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.