The Material Composition And Tectonic Deformation Characteristics Of The Southern Kunlun Tectonic Melanges

Distributed in Qinghai-Tibet Plateau of the northeast Kunlun orogen, northernQaidam Basin and southern Ba yan Har orogenic belt,It is an important part in thearea of the central orogen. Based on the structural section in Xiaonanchuan andXueshuihe area through the field geological survey and indonic study, we finished thecomprehensive study of the tectonic melanges in the southern Kunlun. Due to itsspecial geography and tectonic position,Chinese and foreign geological scholars haspay more attention to it. We made an important, interdisciplinary and comprehensiveresearch. We have presented the following understanding and progress:1. We identify five different rock mass and two related to the matrix of thetectonic melanges in the southern Kunlun. Rock mass can be divided into two types:island arc and the related arc basin in ancient building reek sand MesoproterozoicWanbaogou Group. Mesoproterozoic Wanbaogou Group rock is subdivided intoamphibolite and blocky marble；Island arc and the related arc basin in ancient buildingreek sand is subdivided into silty slate,foliated pyroclastic rock and platy tuffite. Thematrix is divided into two types: One is that related with wanbaogou Group matrixand another is island arc and the related with arc basin building matrix.2. Wanbaogou Group (Amphibolite and Blocky marble) may form in the settingof continental rift, weighted mean age of1123±110Ma, which is Mesoproterozoic.3. Silty slate, foliated pyroclastic rock, platy tuffite are a set of arc basin formedunder the system of volcanic sedimentary built. It is probably the product of the EarlyPaleozoic oceans subduction, after many tectonic actions of a superposition compositecollage. Weighted age of volcanic island arc is499±11Ma, suggesting that earlyPaleozoic oceanic subduction occurs before the Cambrian.4. Through different rock and matrix internal structural analysis, we think thetectonic mélanges experienced four deformations:①The first stage is the subduction and accretion period, It is characterized byregional penetrative foliation Sn+1and deep ductile shearing deformation(sheath fold, asymmetric shear folds and so on); The hinge of fold is nearly horizontal(Lb:120°∠12°), which reflects nearly N-S trending extrusion movement.②The second period is left type strike-slip shear extrusion, which shows earlydifferentiation pulse body (Calcium) and foliation that folded and lens of body. Thehinge of fold is nearly up-right(Lb:300°∠72°), which reflects nearly NWW-SEEstrike-slip extrusion movement.③The third stage is dextral strike-slip shear deformation which mainly formsbetween the rock mass. It is characterized by etc thick folds, wide slow drape (thehinge of fold is nearly up-right), unsymmetrical fold that overlying early foliation, andcleavage and right split ductile shear zone development.④The fourth period is brittle fracture structure, fault plane mainly trended tosouth showed normal faults, give priority to brittle fracture. It reflect the deformationcharacteristics during the plateau uplift.5． The tectonic melanges in the southern Kunlun with present tectonicframework is not a single process in place and emplacement mechanism, but itexperienced at least three times in place before the final process in place. Itsemplacement mechanism mainly is subduction-scrape-adhesion type andsubduction-inversion-adhesion type.