Study On Metamorphic-Deformation Characteristics And Formation Environment Of Luonan-Luanchuan Fault Zone (Luanchuan Section)

Luonan-Luanchuan fault zone is one of the famous fault zone in Qinling orogenic belt,and it is the geological dividing line between north China plate and the qinling orogenic belt.The fault zones strike nearly to EW, it crosses the Luanchuan County, Henan Province, and the rock outcrop is well,it grows Kuanping group quartz micaschist,Taowan group marble and Luanchuan group quartzite.It has important scientific significance for clarifing these rocks' metamorphic deformation characteristics and formation environment for a deeply understanding of the tectonic process and evolution of Luonan-Luanchuan fault zone, as well as further study of the Qinling orogenic belt' formation, evolution and dynamics.It will also play a certain role in promoting the research of ancient plate with collision suture zone and the deformation of modern plate convergence boundary. In this paper, through many kinds of field survey measurements and combined with the test and analysis of varies of modern equipments in the laboratory,we know that the basic trend of the luanchuan section of Luonan-Luanchuan fault zone is 13 to 30 degrees, the dip angle is 58 to 89 degrees, in the south side of the fault zone, the occurrence changed due to the influence of late brittle fracture. The trend lineation and horizontal lineation of Luonan-Luanchuan fault zone (Luanchuan section) are development. Combined with the ancient paleotectonic stress state recovery,wo know that it has the nature from the north to the south of thrust, with sinistral shearing. The main deformed minerals are quartz, calcite, biotite and muscovite,the deformation mechanism dominated by quartz bulging of dynamic recrystallization and calcite mechanical twinning and subgrain rotation deformation,the mineral paragenesis combination relations indicate the metamorphic facies of greenschist facies. Through the mechanical twinning of calcite and the phengite pressure gauge,we know that the metamorphic temperature of Taowan group marble is higher than 200 degrees,and the metamorphism pressure is around 0.4GPa to 0.7GPa. Ti tempreture gauge in biotite-muscovite measured metamorphic deformation temperature of Kuangping group schists and part of the Taowan group marble is 440 ? to 520?,the metamorphic deformation pressure is about 0.3 GPa to 0.5 GPa. Through EBSD technique,we know that the marble's preferred orientation in the south of Luonan-Luanchuan fault zone (luanchuan section) is higher than the north,so the southern metamorphic temperature is higher than the northern. Comprehensive above several temperature and pressure measurements, we can draw that the metamorphic deformation environment of Luonan-Luanchuan fault zone (luanchuan section) is the greenschist facies in low temperature, medium pressure to the epidote amphibolite facies.