The Analysis Of Early Paleozoic Era Rock Deformation Characteristics In Kaladawan Area,Northern Altun

The Kaladawan area located in the Middle-eastern of Altun northern,Which is bounded by the north Altun Tagh fault and the Altun fault on the south.Geotectonically,it belong to the subduction-collision zone of the early Paleozoic Dunhuang block and the central Altyn Tagh block.This paper focuses on the characteristics of rock deformation in this area.In order to probe into the strain pattern and deformation conditions of Kaladawan area,Altun northern,this paper mainly carried out structural deformation characteristics on deformed rocks.Based on detailed field geological observation,some oriented samples were collected along the section of Kaladawan.And detailed research is conducted on the magnetic fabric characteristic in the area.Meanwhile,the microstructural analyses and EBSD fabric are taken to strong deformation rock of magnetic samples.The magnetic fabric results show that anisotropy degrees of the magnetic susceptibility(P')are relatively large which indicate the strong structural deformation of Kaladawan area.In addition,the lower hemisphere equal area stereographic projection of Magnetic susceptibility ellipsoid principal axis and The Class Flinn diagram demonstrates that the whole region is affected by the southern and northern compressive stress,which is characterized by the strain of flaser type.However,the strain ellipsoid in the middle part of the study region which develop steep dip line shows an elongated strain type.Moreover,the microstructure feature and EBSD elongated strain type.EBSD fabric reflect that the deformation of Kaladawan is mainly the prismatic(10(?)0)<11(?)0> under medium temperature conditions(400~500?).However,the prismatic(10(?)0)<0001> glide at high temperature conditions(500~600?)is overlapped on south of the study region.Meanwhile,basal(0001)<11(?)0> glide at low temperature conditions(300~400?)is overlapped on local area.What's more,the emergence of superposition deformation is manifested by the gradual transition of high-temperature deformation to low-temperature deformation.LA-ICP-MS zircon U-Pb dating for the Kaladawan Magnetite-containing conglomerate which occur on the middle of Kaladawan section yields a peak age of 510.22 Ma.While the peak age of northern conglomerate is 456.75 Ma.The age of the detrital zircon from north to south shows the trend of getting older.Through previous studies,SHRIMP zircon U-Pb results of the non-entangled granite body in Altun northern is 427~417Ma.In addition,LA-ICP-MS zircon U-Pb dating for felsic mylonite which occur on the south yields an age of 477.6±4.9Ma.And while the LA-ICP-MS zircon U-Pb dating for mylonitization diorite which occur on the north yields an age of 478.1±2.1Ma.These isotopic geological data indicate that the rock deformation in the region is formed in 477~427Ma and is in a process of continuous change from subduction to collision.To sum up,the subduction-collision of the Dunhuang block and the central Altyn Tagh block in 477~427Ma cause a lasting influence on Kaladawan area,Altun northern.It shows medium temperature(400~500?)prismatic(10(?)0)<11(?)0> slid deformation which mainly caused by flaser type strain.However,with the gradual increase of the subduction angle and the effect of the drag force of the mantle convection,the rock in the middle of the study region transform the extrusion stress of near north-south direction to the tensile stress along the steep slope slab,forming a series of elongated strains.