The identification of Early Cretaceous Baoder extensional granitic dome in Sonid Left Banner, Inner Mongolia, and its tectonic implications

Located in the China-Mongolia border area of Sonid Left Banner, the Baoder dome is an asymmetric syn-kinematic extensional dome. This dome consists of core Early Cretaceous granitic pluton, ductile shear zone and brittle detachment fault from center outwards. The hanging wall consists of undeformed Early Permian granodiorite, Devonian schists and Early Cretaceous basin. Ductile shear zone and detachment fault are only developed in the southwestern part. Detailed field observation and microstructures show that core pluton and ductile shear zone were formed in the same tectonic stress field, suggesting a unified top-to-the-NW shearing. The deformation grade increases outwards. All these characteristics imply that the foliations of the dome were genetically closely related to the emplacement and uplift of the pluton. Thus, the Baoder dome is similar to other extensional domes in Northeast Asian, which reflects geological features of syn-kinematic granitic dome during the regional extensional detachment setting.