3D Modeling and the Age of the Collision Metamorphism of the Khan-Khukhei Block, Northern Mongolia

The reconstruction of the Early Paleozoic collision metamorphism of the Khan-Khukhei Block (Northern Mongolia) based on 3D modeling of thermal state of the crust and isotope dating is presented. The age of garnet–biotite schist from a metamorphic complex of the Khan-Khukhei Block of 517.4 ± 7.4 Ma is determined for the first time. 3D modeling was conducted to compare this age of metamorphism with the available age determinations of (post-) collision granite formation in the range of 513‒505 Ma. The model considers radiogenic heating at an elevated heat production of rocks of the thickened crust of the Khan-Khukhei block as the cause of the migmatization and granitoid melts formation. 3D modeling was conducted for the first time for thermal-dome type of metamorphism. The results provide a realistic conception of magma generation in typical collision settings in the absence of mantle magmatic heat sources. The time interval between metamorphism and the stage of anatectic magma formation is 5–12 Ma.