Granitic protrusions in the structure of intraplate reactivation, southern Mongolia

Abstract

The paper describes tectonic assemblies determining structure and kinematics of the plate evolution in the eastern segment of the Gobi Altay and Gobi Tien Shan intraplate reactivation zones in southern Mongolia. These zones are characterized by deformations corresponding to a 3D brittle-ductile shear flow. The structural and compositional reworking is most strikingly expressed in certain varieties of granites, which form specific geostructures called crystalline protrusions. The internal structure of protrusive bodies is distinguished by fragmentation differing in scale, intense brecciation, cataclasis, and structural-mineral reworking of rocks. Taken together, these phenomena facilitate the tectonic mobility of rock masses under low-temperature and hypabyssal conditions and maintain 3D tectonic flow in basement rocks. The tectonic style of the region and its evolution are predetermined by the 3D flow of granitoids in the crystalline basement, which is related to the joint action of various mechanisms discussed in this paper.