Deformation And Evolution Of The Tectonic Melange Belt Along The Central Eastern Kunlun Of (East Part) Eastern Kunlun Orogen

The Eastern Kunlun orogenic belt belong to middle of the Central Orogenic System, Charactered by multi- cycle collision orogeny. The orogenic belt experienced multiphase tectonic superposition and transformation, it has the diversity of orogenic type, the complexity of the structure, the activities of long-term and so on. The tectonic melange belt along the central Eastern Kunlun is located within the East Kunlun orogenic belt. Tectonic deformation is very complex, it recording deformation events with different period(time) and the different characteristics, as an important area of Chinese mainland of multi-block split formation and dynamics and structure of space-time domain conversion, it is an ideal test site of study original and Paleo-Tethys Ocean-continental tectonic evolution and composite orogenic. This paper by structural geology, petrology, sedimentology, zircon U-Pb geochronology and rock fabric science and other methods, on the geometry, kinematics and dynamics were studied in detail of the tectonic melange belt along the Central Eastern Kunlun of(East Part)Eastern Kunlun Orogen, We mainly have the following understanding and progress:1、Tectonic melange belt along the Central Eastern Kunlun of(East Part)Eastern Kunlun Orogen of deformation is divided into 7(times),by actual construction of 8 profiles with a detailed study of the field and after the room in tectonic melange belt:(1)The first phase(time) tectonic deformation(D1) in the mid-Neoproterozoic(early Jinningian), it is expressed as under the north-south contraction mechanism, generated penetrative foliation(S1), that shows a deep plastic flow characteristics, metamorphism roughly amphibolite facies- granulite facies.(2)The second phase(time) tectonic deformation(D2) produced in the late Early Paleozoic in the north and south sides zone land mass subduction squeeze environment of the central fault of East Kunlun, form the initial reason for the deformation of tectonic level to the various thrust properties of deep plastic deformation structure combination. we through the foliation and stretching lineation occurrence calculations, obtaining its ancient stress field orientation is NE-SW(σ1:189°∠1°) direction, dynamic recrystallization and the subgrain size average estimation to obtain the stress value is 383.43 MPa, after the quartz c-axis fabric and minerals(feldspar, quartz) microscopic structure(dynamic recrystallization type) features a detailed study to obtain the metamorphic deformation temperature 500 ℃ ~ 650 ℃(High greenschist facies- low amphibolite facies), Corresponding to an average strain rate of 1.38×10-8 s-1, reflects tectonic melange in the environment of high temperature and pressure to deform, with a high Strain rate. Using the instantaneous strain elongation axis method to calculate the instantaneous kinematic vorticity, quartz c axial fabric combination of oblique foliation method to obtain the instantaneous vorticity, quartz c axial fabric combines finite strain gauge for the average vorticity and c’ method is used to obtain the instantaneous kinematic vorticity value Were 0.69 ~ 0.79, 0.25 ~ 0.82 and 0.82 ~ 0.32, and 0.27 ~ 0.36, performance for different from early to late stage of kinematic vorticity value from large to small, instantaneous strain elongation axis and quartz c axis instantaneous vorticity value close, and there were more than 0.75 and less than 0.71 samples, Instructions supplied in pure shear and simple shear components of strain in shear band occur simultaneously or at least in part, at the same time, it is on both sides of the east kunlun tectonic melange belt oblique convergence between continental extrusion strain as a result, Quartz c axial fabric is rhombic symmetry or weak rhombic symmetry also confirms this phenomenon.(3)The third phase(time) tectonic deformation(D3) formed in a collision split comprehensive background of the central fault of East Kunlun in the north and south sides of the continental in the late palaeozoic, the formation of left-lateral slip shear properties of in-depth of plastic deformation structure combination, palaeostress field orientation for E- W(σ1: 89°∠36°), average stress value is 288.48 MPa, the ancient metamorphic deformation temperature is 500 ℃ ~ 530 ℃(high green schist facies), the corresponding average strain rate of 3.0×10-11 s-1, it reflects the tectonic melange belt in the period for high temperature deformation of the high pressure environment, strain rate is higher, but the strain rate is much lower than subduction stage.(4)The fourth period(time) tectonic deformation(D4) in the late Permian to early Triassic, the south ocean subduction and gathering phase of Buqingshan-A′nyemaqen ocean, the formation of various kinds of plastic deformation structure combination with thrust shear properties, palaeostress field orientation for NW- SE(σ1: 333°∠21°), average stress value is 317.48 MPa, the ancient subject metamorphic deformation temperature is 480 ℃ ~ 530 ℃(green schist facies), and the corresponding average strain rate of 6.41×10-9 s-1, that reflects the tectonic melange belt in the period for high temperature deformation of the high pressure environment, has the very high strain rate.Use different methods to obtain kinematic vorticity value were 0.72 ~ 0.81, 0.62 ~ 0.99 and 0.99 ~ 0.85, and 0.37 ~ 0.51, also different from early to late stage of kinematic vorticity value from big to small change, the characteristics of the instantaneous strain elongation axis and quartz c axis instantaneous vorticity value close, and there were more than 0.75, the sample is less than 0.71 instructions supplied in pure shear and simple shear components of strain in the shear zone occurs at the same time or at least in part, at the same time, castle peak is cloth- o nima qing between tectonic melange belt on both sides of the continental oblique compression strain results.(5)The fifth(time) tectonic deformation(D5) formed in Triassic and in the collision under the background of comprehensively of the south side Bayan Har block with East Kunlun block, which with the right strike-slip shear properties in the shallow level of brittle-ductile structural combination.This period of ancient tectonic deformation stress field orientation for E- W(σ1:89°∠45°), the average stress value is 321.57 MPa, the ancient metamorphic deformation temperature is 480 ℃ ~ 500 ℃(low green schist facies), and the corresponding average strain rate of 4.49×10-11 s-1,These reflect the tectonic melange belt in the period for medium temperature deformation of the high pressure environment and high strain rate.Using different methods to obtain kinematic vorticity value were 0.56 ~ 1.00, 0.59 ~ 0.91 and 0.91 ~ 0.74, and 0.19 ~ 0.31, It still has different from early to late stage characteristic of kinematic vorticity value from large to small.(6)The sixth(times) tectonic deformation(D6) in the end of late Triassic orogenic stage after geological background, the generated light- surface ductile- brittle structure combination of left- lateral slip deformation.The period average stress value is 346.47 MPa, the ancient metamorphic deformation temperature is 380 ℃ ~ 480 ℃(low green schist facies), and the corresponding average strain rate of 1.06×10-11 s-1, these reflect the tectonic melange belt in the period for deformation of high pressure in low temperature environment, strain rate is higher, but the earlier stage several tectonic deformation strain rate are low.(7)The seventh(sub) tectonic deformation(D7) formed after the Late Triassic, under the NE-SW(σ1: 47° ∠20°) to extrusion stress mechanism, formed a set of brittle shallow-surface structure combination, the period of ancient stress field direction and printed today-the plate subduction collision stress orientation is roughly same, showed that the late ductile brittle- brittle left strike-slip shearing action of the power supply may come from the print-the plate subduction collision.2、A suit of metamorphism-deformation sedimentary strata exposed at Hatugou of Balong area in Eastern part of eastern Kunlun,the north to change complex composition conglomerate in southern section. which northern for variable polymictic conglomerate segment,the southern for metamorphism clastic section.We through the study of the finite strain measurement of deformation conglomerate, the results show, Flinn index(K1) and the logarithm Flinn index(K2) are greater than 1, indicating that the geological deformation features an elongated type strain; ② the greater the(K/γ/ε) and r value the closer to the main fault of central East Kunlun; ③ conglomerate deformation amount of stretch along the X-axis direction is 167%-260%, Y-axis direction shorter 24% ~ 43%, Z-axis direction shorter 45% to 62%. Through this metamorphism-deformation sedimentary gravel composition statistics、after a comprehensive analysis of gravel sorting coefficient(1.24~1.42)and gravel gravel degree tablets and other features,as we see it with characteristics of near-source and fast stacking.This article Use of LA-MC-ICP-MS zircon U-Pb dating of micro-technology,get sericite-albite-quartz schistvariant of Polymictic conglomerate detrital zircon U-Pb isotopic ages,to explore the formation age and material source characteristics of the deformed sedimentary. The detrital zircon age spectrum can be divided into six groups :①Nanhuaan—Sinian age group,751~602Ma,the peak value is 674 Ma,the group zircon ages corresponding to the Late Neoproterozoic magmatic events age in EKOB,and associated with Rodinia supercontinent breakup event,The smallest zircon age of 602 Ma, indicate sedimentary strata formed time should be later than 602Ma; ②Late Mesoproterozoic—mid-Neoproterozoic age group,1146~783Ma,there are peak value is 788 Ma 、 947 Ma and 1115 Ma, the zircon ages group can compare in late Mesoproterozoic—mid-Neoproterozoic magmatic events of EKOB,on behalf of the East Kunlun area in response to the global scale convergence event of Rodinia;③Late Mesoproterozoic age group,1399~1180Ma,the peak value is 1318 Ma,zircon age group may be related to the East Kunlun tectonic belt late Proterozoic magmatic events;④early Proterozoic age group,1712~1553Ma,the peak value is 1556 Ma,the group of age represents the source region thermal event in the early Proterozoic;⑤late Neoarchaean—early Paleoproterozoic age group,2530~2347Ma,the peak value is 2518 Ma,zircon age of the group within the East Kunlun orogenic late Neoarchaean—early Palaeoproterozoic age of roughly the same magmatic event, indicating that the late Neoarchaean—early Paleoproterozoic magmatic material of EKOB also provides detritus for the metamorphic strata of Hatu ditch;⑥Archean age group,3230~2763Ma,indicate the provenance of metamorphism-deformation sedimentary strata presence the Paleoarchean continental nucleus.Through analysis of the metamorphic rocks detrital zircon ages and provenance characteristics showed that is not thesame the Devonian Maoniushan group by predecessors classified,the main form should belong to the late Sinian.Geochronology data combined with gravel composition after statistical analysis,this article hold that variable polymictic conglomerate layer material of Hatu ditch in Balong area comes mainly from the Baishahe groups, Xiaomiao groups, Wanbaogou group of Precambrian and metamorphic granitic gneiss of Mesoproterozoic—Neoproterozoic in the East Kunlun orogenic belt.