Deformation Characteristics And Emplacement Mechanism Of Linglong Granite In Jiao Dong

Linglong granite is the main host rock of gold ore concentration area in Northwest Jiao Dong.Most of the discovered gold deposits or occurrences are located in Zhao Ping fault zone and Jiao Jia fault zone on the east and west edge of the rock mass.Previous work mainly focused on the study of mineralogy and petrology.However,the emplacement and tectonic deformation of granites recorded the dynamic process of orogenic belt evolution.The emplacement dynamics study is of great significance for revealing the tectonic evolution of orogenic belt and guiding regional mineral exploration.On the basis of detailed field geological survey and indoor microscopic observation,this paper makes a systematic study on petrography,microfabrics and magnetic fabric,and discusses the emplacement mechanism of Linglong granite.(1)According to the occurrence and petrological characteristics of magmatic rocks,the Linglong granite is divided into four parts:the Northern,Middle,Middle-Southern,Southern segments.The long axis of the Northern segment is NE trending,the central facies is medium coarse grained garnet bearing biotite monzogranite,and the marginal facies is weak gneissic medium grained garnet bearing biotite monzogranite;The long axis of the Middle segment is NNE trending,the central facies is medium coarse grained Muscovite bearing biotite monzogranite,and the marginal facies is gneissic medium grained Muscovite bearing biotite monzogranite;The long axis of the Middle-South segment is NE trending,and its lithology is gneissic medium fine grained garnet bearing biotite monzogranite;The major axis of the Southern segment is NNE,the central facies is medium coarse grained Muscovite garnet bearing biotite monzogranite,and the marginal facies is gneissic medium fine grained Muscovite garnet bearing biotite monzogranite.(2)The observation under the microscope and magnetic susceptibility anisotropy measurement,it is revealed that the average volumetric magnetic susceptibility(K_mean)of the Northern,Middle,Middle-Southern segments of the rock mass is 4.25?1798×10^-5 SI,which is ferromagnetic granite;and K_mean of the Southern segment is 3.79?21.05×10^-5 SI,which is paramagnetic granite.The corrected susceptibility anisotropy(Pj)is 1.04?1.34,and Pj value increases from center to edge phase,indicating that the deformation degree of the central phase of each rock mass is lower than that of the East and west edge facies;The shape parameter(T)is 0<T<1,and the flattening ratio(E)is mainly E>1 mainly,indicating that the rock mass is mainly flat strain.(3)The results of the anisotropy measurement of the magnetic susceptibility show that the occurrence of magnetic lineage and magnetic foliation texture in each section is different.The North segment of the magnetic lineation is plunging to NW and SE with the plunge angle of5?28°,the trend of magnetic foliation is NE,and the dip angle is 6?33°;The magnetic lineation of the central phase in the Middle segment plunging to NE with the plunge angle of 63?85°,the trend of magnetic foliation is mainly NW with dip angle of 64?85°,the East and West marginal facies magnetic lineations are plunging to NE and SW with the plunge angle of 29?72°,the trend of magnetic foliation is NE and the dip angle is 62?81°;The magnetic lineation in the Middle-South section is segment to NW and SE with plunge angle of 23?65°,the trend of magnetic foliation is NW and the dip angle is 60?87°;The magnetic lineation of the central facies and the eastern marginal facies in the Southern segment plunging to SE with the plunge angle of 74°and36°,The trend of magnetic foliation is NE and the dip angle is 62°and 39°,The magnetic lineation of the western margin is plunging to NE and SW with the plunge angle of 9?46°,The trend of magnetic foliation is NE and the dip angle is 34?47°.(4)The magma of Linglong granite body was injected and emplaced along the active low angle fault zone,and induced emplacement is the main emplacement mechanism.In the NW-SE extensional tectonic setting,the regional pressure decreased sharply,which induced the magma to locate along the low angle fault zone.Under the left lateral shear of Jiao Jia fault and Zhao Ping fault,syntectonic deformation developed in the eastern and western marginal facies of Linglong granite,which may lead to the lateral compression of the rock mass due to the magma intrusion velocity higher than the spatial formation velocity.