Difference of the syn–tectonic magmatic flow and granite emplacement under stable tectonic environment and its constrain on the Late Paleozoic to Early Mesozoic tectonic evolution in the northern margin of North China plate

Granitic magma constitute the important components of continental crust, a lot of researches have done on the structural deformation and fundamental framework of the Yanshan area on the northern margin of the North China plate. However, dynamic setting of granite intrusions was less studied. Different from granite intrusions in relatively stable tectonic setting, syn–tectonic magmatic flow usually occurs in active tectonic zones such as continental margin and orogenic belt, the characteristics, intrusion process and flow direction of syn–tectonic granite are usually complicated affected by strongest tectonic stress field. Large quantities of granitic magma intruded in the northern margin of the North China plate during the Late Paleozoic, and their tectonic properties and analysis provide crucial evidence for the study of subduction of Paleo−Asian Ocean and the destruction of the North China plate. By analyzing the structural deformation and petrographic characteristics of Danguangding pluton and Panshan pluton in the northern margin of North China plate from macro to micro, semi–quantitative mineralogical study was combined with electron microprobe, and the pressure conditions of pluton formation are calculated by using hornblende manometer to obtain the depth of granite intrusions, and the tectonic setting in the northern margin of the North China plate under different dynamic backgrounds is discussed. On the outcrop scale, the granodiorite shows a large number of rootless folds with a north axial direction and low axial plane angle, and the long axes of inclusions and xenoliths are parallel to the flow foliation. Under the microscope, dark minerals such as amphibole and biotite can be seen in directional arrangement, with typical syn–tectonic deformation characteristics. The crystallization pressure of the all–aluminum gauge of amphibole is 3.62~5.64 kbar. Corresponding to the depth of the middle crust (12.86~22.99 km), it is believed that during the Late Paleozoic (320~290 Ma), the middle and lower crust on the northern margin of the North China plate remelted to form a syn–tectonic magmatic flow from north to south, which also provided a medium for the stress transfer in the middle and deep layers. This indicates that the remelting of the middle and lower crust on the northern margin of the North China plate in the Late Paleozoic was formed by syn–tectonic magmatic flow from north to south, which formed the Daguangding pluton and also provided a medium for the stress transfer in the middle and deep layers. The inclusions and xenoliths in Panshan granite are not deformed in Mesozoic, and there is no directional arrangement of dark minerals, marble is formed by thermal contact metamorphism in the contact zone between pluton and surrounding rock, which belongs to granite intrusions in relatively stable tectonic setting.