Study Of Structural Deformation Characteristics Of Upper Paleozoic,in Gipp Area,Tibet

Paleozoic strata of the South Qiangtang block was developed in the north of Ritu county in Ali and Gangmacuo area in the north of Gaize county and the hot spring ditch of Rongma county.The article is theoretically based on the hyperplasia theory,and its research method is tectonic analysis,through large measuring scale tectonic and lithologic mapping and tectonic and lithologic profile survey in the wild,the writer combined it with interior microscopic structure and strain measurementand and detrital zircon isotope chronology.The article gives system research on late Paleozoic structure deformation in research area,the research result is significant to confirm structure properties of Qiangtang area and evolution of Bangong Nujiang Suture Zone.Through the research of detrital zircon geochronology,the writer thinks that age characteristic curve of detrital zircon of clastic rock and late Paleozoic in the research area are the same.So the writer comes to a conclusion that the stratum is in the late Paleozoic,and then the article will analyze its provenance characteristics.On the basis of system tectonic analysis,the writer found that late Palaeozoic strata in Jipu region of Ritu county in South Qiangtang area developed penetrative cleavage(S1),the article builds the foliation of penetrative cleavage and builds tectonic styles of related structural substituted.The article gives the conclusion that in the fold between mudstone and sandstone,the fold with argillaceous rock as its turning end is chevron fold which developed positive sector continuous cleavage,the fold with the sandstone layer as the transition end is smooth isopach fold which developed anti sector spaced cleavage.Through observation and research in wild,the period of tectonic deformation in the research area is divided into three stages,the first stage is buckling which formed the regional penetrative cleavage(S1),and it is thought to be related to the function of Paleo-Tethys Ocean subduction,forming nearly east-west fold which has the same direction as early-formed penetrative cleavage(S1);The middle stage is also buckling,which direction is as near as early-formed folding,performing coaxial stack on an earlier structural deformation,refolding the localcleavage of S1,forming nonpenetrating cleavage S2,and it is thought to be related to the function of Paleo-Tethys Ocean closed impact extrusion;The last stage is thrust-nappe structure,which developed a large number of thrust fault and related kink structure(cleavage S3),the article found that the closer the distance from the thrust plane,the stronger deformation of the kink structure and the greater the amplitude of kink structure,the deformation in this region is consistent with the Cenozoic thrust-nappe structure,and is associated with the collision between the India plate and the Asian plate.Through a large number of observation of kink structure and the research of microstructure in the research area,the article divided the kink structure into 4 kinds and confirmed the tentonic characteristics in outcrop and microscopic.The article calculates the strain reduction of this formation is 31.3%through strain state measurement of strongly deformed gravel in fold hinge zones and undeformed gravel in limbs of the fold.