Magmatic Flow And Deformation In Typical Tectonic Environment

How to identify magmatic flow intruded in the metamorphic basement, and how to distinguish the differences among magmatic flow and metamorphic gneiss and mylonite along the ductile shear zones in outcrop scale and microscope scale, are re-considered issues of modern petrology and structural geology. According to comparing the features of magmatic flow/submagmatic flow, combining with the research of magmatic flow and solid-state flow all over the world, we identified magmatic flow which formed in the late magmatic emplacement during cooling crystallization process from metamorphic basement.This dissertation focuses on the syn-contraction magmatic flow in the northern margin of North China block intruded in Late Carboniferous, syn-extensional magmatic flow in Liaonan area intruded in Early Cretaceous and syn-strike-slip shear magmatic flow in coastal area of Fujian intruded in Early Cretaceous. Giving criteria for structures and microstructures produced by magmatic flow according to the macroscopic, microscopic petrology and mineralogy characteristics of magmatic flow intruded in mid-lower crust. This dissertation uses U-Pb zircon and 40Ar/39Ar dating to constrain the magmatic flow time series. Based on the geochronology and deformation chronology of magmatic flow, we analyze the transport, emplacement and late deformation of magmatic flow. Moreover, hornblende-plagioclase temperature-pressure gauge is used to estimate their emplacement depths.During the late Paleozoic, the ancient Central Asian ocean subducted beneath the North China Plate, resulted in the northern margin of North China to become an active continental margin, forming a large number of intrusive rocks. The results of U-Pb zircon dating indicate that the plutons emplaced at 320-290 Ma. The similar ages of the cores and the gneiss mean that the zircons inherited from the old rocks. The magmatic plutons have been piled up by the ductile shear deformation, and the muscovite 40Ar/39Ar dating yields the deformation occurred at ～250 Ma. The ductile shear zone present to different rocks indicates that it has piled up on the gneiss and the plutons. Hornblende geobarameter indicates that the magmatic flow formed in the mid-lower crust at a depth of 19-25km. The ages and the features of magmatic flow show that the northern margin of the North China block was compressional tectonic setting from north to south at Late Carboniferous.Canchang granodiorite in Jinzhou area, Liaoning Province is a syn-extension pluton formed in Yanshanian time. The outcrop shows intense stretching magmatic flow features, including magmatic foliation, magmatic lineation and magmatic folds, indicating that the pluton is mainly affected by the vertical gravity collapse (extensional structure). The results of U-Pb zircon dating confirm that the magmatic flow formed at 132-124Ma. A large of magmatite intrusion and extensional deformation developed in the Early Cretaceous, show that the subduction of the Pacific plate lead to subsequent lithospheric scale extensional collapse and mantle asthenosphere upwelling and re-melting of the lower crust resulted in a deal of stretching magmatic flow.The granotoids developed along Changle-Nanao ductile shear zone in the coastal area of Fujian Province are syn-transcurrent magmatic flow/submagmatic flow. Using U-Pb ziron dating to constrain the magmatic flow, we got mean ages of 100-130Ma and the mafic dikes age also ～100Ma. The results show that the emplacement process of granotoids is not single, but with magma mixing. Using hornblende-plagioclase geothermal barometer to estimate the pressure-temperature condition, the results indicate that the magmatic flow formed in the mid-lower crust.