Deformation Structures of the Madao Gneiss in South Qinling: Structural Analysis, Geochronological Constraints, and Tectonic Implications

The tectonic evolution of South Qinling,which is a main part of the Qinling orogenic belt,is still in dispute and deformation history of South Qinling is poorly studied.In this paper,detailed structural,microstructural,quartz c-axis fabric analysis,and geochronology results for the Madao gneiss in South Qinling are presented to characterize the deformation history.Results show that rocks in the northern part(Tiefodian-Laozhanggou) experience general shearing and deform at relative low temperature.The shear sense generally is south to north.In contrast,rocks in the southern part(Laozhanggou-Panjiahe) are weakly sheared with pure shear features and evidence of hightemperature deformation.Based on the analyses,we conclude that there exist two distinct deformation geometries in the Madao gneiss and accordingly we can divide the deformation into two stages.The early stage is represented by regional shortening,while the late stage features northward thrust shearing and evidence shows that it was a progressive process between them.LA-ICP MS U-Pb dating of zircons from pre-deformational migmatite veins yields age of 198.5 ± 2.0 Ma.This result,in combination with the age of post-deformational granite,indicates that the northward thrust shearing of the Madao gneiss occurred in the Late Triassic.In view of these results and other reported data in South Qinling,we propose that deformation in Madao gneiss may result from the initial collision and subsequent northward accretion in Late Triassic.     

Intracontinental Orogenic Igneous Rocks and Orogenic Processes in Qinghai-Xizang-Himalaya

Based on the discussion on the intracontinental orogenic igneous rocks formed after India- Asia collision (40 or 45 Ma ),the intracontinemal orogenic processes of Qinghai-Xizang (Tibet)-Himalaya are traced . Muscovite/two mica granite is considered as a petrological record of intracontinental subduction. Volcanic rocks of shoshonite series are believed to be the products of the orogenic and outside cratonic lithosphere convergence . The intracontinental orogenic igneous rocks are developed only on the margins of the orogenic belt. The pairing phenomenon of the igneous rock zones is regarded as one of the best signs to recognize the special range of orogenic belt . The stage of magmatic activity is a representation and indicator of orogenic episode . Three pairs of the igneous events in Oligocene , Miocene and Pleistocene and their space distribution indicate three corresponding orogenic episodes and the horizontal expansion across the orogenic belt , respectively , On the northern and southern margins of     

Kanfenggou UHP Metamorphic Fragment in Eastern Qinling Orogen and Its Relationship to Dabie-Sulu UHP and HP Metamorphic Belts, Central China

In the Central Orogenic Belt, China, two UHP metamorphic belts are discriminated mainly based on a detailed structural analysis of the Kanfenggou UHP metamorphic fragment exposed in the eastern Qinling orogen, and together with previous regional structural, petrological and geochronological data at the scale of the orogenic domain. The first one corresponds to the South Altun-North QaidamNorth Qinling UHP metarnorphic belt. The other is the Dabie-Sulu UHP and HP metamorphic belts. The two UHP metamorphic belts are separated by a series of tectonic slices composed by the Qiniing rock group, Danfeng rock group and Liuling or Foziling rock group etc. respectively, and are different in age of the peak UHP metamorphism and geodynamic implications for continental deep subduction and collision. Regional field and petrological relationships suggest that the Kanfenggou UHP metamorphic fragment that contains a large volume of the coesite- and microdiamond-bearing eclogite lenses is compatible with the structures recognized in the South Altun and North Qaidam UHP metamorphic fragments exposed in the western part of China, thereby forming a large UHP metamorphic belt up to 1000 km long along the orogen strike. This UHP metamorphic belt represents an intercontinental deep subduction and collision belt between the Yangtze and Sino-Korean cratons, occurred during the Paleozoic. On the other hand, the well-constrained Dabie-Sulu UHP and HP metamorphic belts occurred mainly during Triassic time (250-220 Ma), and were produced by the intracontinental deep subduction and collision within the Yangtze craton. The Kanfenggou UHP metamorphic fragment does not appear to link with the DabieSulu UHP and HP metamorphic belts along the orogen. There is no reason to assume the two UHP metamorphic belts as a single giant deep subduction and collision zone in the Central Orogenic Belt situated between the Yangtze and Sino-Korean cratons. Therefore, any dynamic model for the orogen must ac-count for the development of UHP metarnorphic rocks belonging to the separate two tectonic belts of different age and tectono-metamorphic history.     

Polyphase Tectonic Events and Cenozoic Basin-Range Coupling in the Tianshan Belt, Northwestern China

Studies show that the Tianshan orogenic belt was built in the late stage of the Paleozoic, as evidenced by the Permian red molasses and foreland basins, which are distributed in parallel with the Tianshan belt, indicating that an intense folding and uplifting event took place. During the Triassic, this orogenic belt was strongly eroded, and basins were further developed. Starting from the Jurassic, a within-plate regional extension occurred, forming a series of Jurassic-Paleogene extensional basins in the peneplaned Tianshan region. Since the Neogene, a collision event between the Indian and the Eurasian plates that took place on the southern side of the Tianshan belt has caused a strong intra-continental orogeny, which is characterized by thrusting and folding. Extremely thick coarse conglomerate and sandy conglomerate of the Xiyu Formation of Neogene System were accumulated unconformably on the Tianshan piedmont. Studies have revealed that the strong compression caused by the Indian-Eurasian collision     

LA–ICP–MS U–Pb Geochronology of Detrital Zircon in the Guanzhong Basin, China and Its Tectonic Response

正Objective The Guanzhong Basin in the transitional zone of the Qinling orogenic belt and the southern margin of the Ordos Basin has been extensively studied in recent years.Although some results have been obtained,some problems such as whether the materials from the North China craton and the Qinling orogenic belt are detrital sedimentary rocks of the Guanzhong Basin still remain unresolved.     

FORMATION AND EVOLUTION OF THE CENOZOIC THRUST FOLD BELT IN JINPING, SICHUAN

The Jinping orogenic belt in Sichuan, China consists mainly of the Jinpingshan intracontinental thrust-nappe belt, foreland thrust-nappe belt and foreland uplift belt. Based on analyses about the characteristics of the structural units in this area, the authors propose in this paper that Chapuzi-Bazhe revival fault belt is the regional boundary fault, and points out that after the formation of the Pre-Sinian basement, the western edge of the Yangtze paraplatform was turned into the passive continental margin in Sinian to Triassic, then into the Mesozoic collision orogenic belt, and finally into the Cenozoic orogenic belt through intracontinental orogeny.     

Structural Characteristics and Formation Mechanism in the Micangshan Foreland,South China

Lying at the junction of the Dabashan, Longmenshan and Qinling mountains, the Micangshan Orogenic Belt coupled with a basin is a duplex structure and back-thrust triangular belt with little horizontal displacement, small thrust faults and continuous sedimentary cover. On the basis of 3D seismic data, and through sedimentary and structural research, the Micangshan foreland can be divided into five subbelts, which from north to south are: basement thrust, frontal thrust, foreland depression-back-thrust triangle, foreland fold belt or anticline belt, and the Tongjiang Depression. Along the direction of strike from west to east, the arcuate structural belt of Micangshan can be divided into west, middle and east segments. During the collision between the Qinling and Yangtze plates, the Micangshan Orogenic Belt was subjected to the interaction of three rigid terranes: Bikou, Foping, and Fenghuangshan (a.k.a. Ziyang) terranes. The collision processes of rigid terranes controlled the structural development of the Micangshan foreland, which are: (a) the former collision between the Micangshan-Hannan and Bikou terranes forming the earlier rudiments of the structure; and (b) the later collision forming the main body of the structural belt. The formation processes of the Micangshan Orogenic Belt can be divided into four stages: (1) in the early stage of the Indosinian movement, the Micangshan-Hannan Rigid Terrane was jointed to the Qinling Plate by the clockwise subduction of the Yangtze Plate toward the Qinling Plate; (2) since the late Triassic, the earlier rudiments of the Tongnanba and Jiulongshan anticlines and corresponding syncline were formed by compression from different directions of the Bikou, Foping and Micangshan-Hannan terranes; (3) in the early stage of the Himalayan movement, the Micangshan-Hannan Terrane formed the Micangshan Nappe torwards the foreland basin and the compression stresses were mainly concentrated along both its flanks, whereas the Micangshan-Hannan Terrane wedged into the Qinling Orogenic Belt with force; (4) in the late stage of the Himalayan movement, the main collision of the Qinling Plate made the old basement rocks of the terrane uplift quickly, to form the Micangshan Orogenic Belt. The Micangshan foreland arcuate structure was formed due to the non-homogeneity of terrane movement.     

A Three—Stage Metallogenic Model for Gold Deposits in Metamorphosed Microclastic Rocks

Gld deposits occurring in metamorphosed microcelastic rocks are distributed extensively at home and abroad.Some deposits of this type are of superlarge tonnage.The formation of gold deposits in metamorphosed microclastic rocks involves three stages:the sedimentary stage,the regionally metamorphic stage,and the ore-forming stage.At the first stage,microclastic sedimentary source rocks were developed in a relatively semi-enclosed reducing sea basin and were enriched in carbon,sulfur and gold.At the second stage,the gold adsorbed on organic matter and clay minerals was relesed and poorly concentrated during the destruction of organic matter and the depletion of clay minerals by regional metamorphism with increase temperature and pressure.At the third stage,a tectono-hydrothermal event took place.As a result,gold was leached from metamorphosed microclastic rocks,transported to ore depositional locus and/or mixed with gold of other sources in the course of migration,and finally precipitared as ores.Gold deposits of this type were eventually formed at the third stage,and they also can be classified as the orogenic belt type and the activation zone type.The gold deposits occurring in metamorphosed microcalastic rocks are the products of reworking processes and the influence of magmatism should be taken into consideration in some cases.     

Tectonic Units and Their Fundamental Characteristics on the Northern Margin of the Alxa Block

The northern margin of the Alxa block is the junction of a tectonic units. Four first-order tectonic units are distinguished: 1. the Yagan structural zone characteristic of an immature island arc; 2. the Zhusileng-Hangwula structural zone, which was a passive continental margin in the Early Palaeozoic and was transformed into an active continental margin in the Late Palaeozoic;3. the Shalazha structural zone characteristic of a mature island arc; 4. the Nuru-Langshan structural zone, which was a Proterozoic orogenic belt and later evolved into an extensional transtional crust in the Palaeozoic. The above-mentioned tectonic units differ remarkably in sedimentary formations, magmatic rock associations, metamorphism and geochemistry and are bounded by faults between one another.     

Deformation of the Shirenshan Block in the North Qinling

<正>Objective The Qinling orogenic belt is a typical complex continental orogenic belt which has experienced multiperiod tectonic evolution and where some important tectonic belts formed.The Luoluan fault is one of the most important belts,which is the boundary fault of the North China Plate and the Qinling orogenic belt.The Shirenshan block is located in the north section between Luanchuan and Fangcheng of the Luoluan fault.The north part is     

Zircon U‐Pb Age of the Shangxu Gold Deposit from Bangong‐Nujiang Co,Northern Tibet,and Restriction on the Early Cretaceous Orogenic Gold Mineralisation

正Objective The Tibetan Plateau is the largest continent-to-continent collision belt in the world.Two orogenic gold mineralisation belts have been recognized in this collision belt,which are as follows:the Indus-Yarlung Zangbo suture zone orogenic gold belt(IYOG),represented by the Mayoumu and Bangbu gold deposits,and the Ailaoshan     

Geochronology,Petrogenesis and Tectonic Setting of the Late Jurassic I-type Granites in the North Qinling Orogenic Belt,Central China

The North Qinling Orogenic Belt(NQOB) is a composite orogenic belt in central China. It started evolving during the Meso–Neoproterozoic period and underwent multiple stages of plate subduction and collision before entering intra-continental orogeny in the Late Triassic. The Meso–Cenozoic intra-continental orogeny and tectonic evolution had different responses in various terranes of the belt, with the tectonic evolution of the middle part of the belt being particularly controversial. The granites...     

Structural and Chronological Evidence for the India-Eurasia Collision of the Early Paleocene in the Eastern Himalayan Syntaxis, Namjagbarwa

The eastern Himalayan syntaxis in Namjagbarwa is a high-grade metamorphic terrain formed by the India-Eurasia collision and northward indentation of the Indian continent into Asia. Right- and left-lateral slip zones were formed by the indentation on the eastern and western boundaries of the syntaxis respectively. The Dongjug-Mainling fault zone is the main shear zone on the western boundary. This fault zone is a left-lateral slip belt with a large component of thrusting. The kinematics of the fault is consistent with the shortening within the syntaxis, and the slipping history along it represents the indenting process of the syntaxis. The Ar-Ar chronological study shows that the age of the early deformation in the Dongjug-Mainling fault zone ranges from 62 to 59 Ma. This evidences that the India-Eurasia collision occurred in the early Paleocene in the eastern Himalayan syntaxis.     

Petrological Study on the Ductile Shear Zones in the Core of the Eastern Qinling Orogenic Belt in Western Henan

A series of ductile shear zones of the overthrust and strike-slip-types and related ductile shear metamorphicrocks, including tectonic melange and mylonites. were formed in the core of the Qinling orogenic belt in thecourse of the Caledonian-Indosinian ductilc and brittle-ductile reworking. The study on their petrography. va-riations in composition and conditions of formation is conducive to revealing the metamorphism-deformationhistory of the core of the Qinling orogenic belt and further to understanding the dynamic mechanism of its evo-lution.     

Sulfur Isotopes Geochemistry of the Nage Cu-Pb Polymetallic Deposit, Southeast Guizhou Province, China

The Nage Cu-Pb polymetallic deposit is located in the transitional zone of the Yangtze craton and cathaysia, that is the southwest of Jiangnan orogenic belt. The mainly strata are Wentong formation of Mesoproterozoic Sibo group and the Jialu formation (Qbj) , Wuye formation (Qbw) , Fanzhao formation (Qbf) and Gongdong formation (Qbg) of the Neoproterozoic Qingbaikou System Xiajiang group.     

Yangshan Gold Deposit:The Largest Carlin and Carlin-like Type Gold Deposit in China

Gold Headquarter of the CAPF has discovered the Yangshan super large-scale gold deposit in Gansu Province, which is a great breakthrough of gold exploration and prospecting in Western Qinling Mountains of China. The gold resources of this deposit achieved 308 tons with increasing potentials. Preliminary geological investigations indicate that the Yangshan gold deposit is located in the intra-continental collision orogenic belt; and the deposit was formed during the continent-continent collision orogenic processes. The geological characteristics of the deposit are similar to that of the typical Carlin-type gold deposits, while differences still exist. The ore-forming background is notably different from the Carlin gold deposit province in the United States; and the ore-forming fluids are similar with that of the orogenic-type gold deposit. Accordingly, the Yangshan gold deposit is a transitional type between the Carlin-type and the orogenic type gold deposits. At present, the Yangshan gold deposit is the largest Carlin and Carlin-like type gold deposit that is ever discovered in China. Researches on metallogeny, metallogenic model and ore-enrichment regularities of the Yangshan gold deposit are crucial to meet the pressing needs of the current geological investigation and ore exploration of the deposit.     

Structural and Geochronological Evidence for Multiple Episodes of Tertiary Deformation along the Ailaoshan-Red River Shear Zone, Southeastern Asia, Since the Paleocene

Structural analyses show that the Ailaoshan-Red River shear zone （ASRRSZ） in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip experienced by the ASRRSZ. The first episode of such deformation occurred throughout the eastern high-grade belt of the ASRRSZ under a transtensional regime and produced L- type tectonites of amphibolite grade. The second episode of left-lateral slip formed high strain zones overprinting the high-grade belt. Its deformational mechanism is similar to simple shear and the deformed rocks are L-S mylonites of greenschist grade. The third episode of left-lateral slip took place chiefly in a western low-grade belt of the ASRRSZ. This deformation occurred in a transpressional regime, formed an overall structure pattern of a sinistral thrust system and produced phyllonites of low-greenschist grade. Geochronological data indicated that the three episodes of left-lateral slip happened before ～58-56 Ma, at least from ～27 Ma to 22 Ma and at ～13-12 Ma respectively. The first episode of slip in the ASRRSZ appeared to correspond to the initial collision of India and Asia at ～60 Ma. The second episode took place almost at the same time as the most intensive compression and uplift in Tibet. The latest event might represent a further eastward material flow in Tibet after ～16-13 Ma. Thus, the ASRRSZ of southeastern Asia probably experienced three main episodes of Tertiary left- lateral slip in the course of intracontinental convergence since the India-Asia collision.     

Deformation Characters of the Maowen Fault Belt in Longmenshan, Western Sichuan

1. Introduction The Longmenshan orogenic belt is a typical intercontinental orogenic belt (Fig. 1), from NW to SE composed of Paleozoic epimetamorphic rock systems, Protozoic intermediate-acid intrusions and metamorphic rocks (called Pengguan Complex), Upper Triassic sandshales, and Paleozoic glided nappe as well as Jurassic-Tertiary molass formation,. The Maowen fault belt is a boundary fault belt between the Longmenshan orogenic belt and Songpan-Garze fold belt. It starts from Shenx…     

http://www.sciencedirect.com/science/article/pii/S1674987114000607

The Qinling Complex of central China is thought to be the oldest rock unit and the inner core of the North Qinling Orogenic Belt （NQOB）. Therefore, the Qinling Complex is the key to understanding the pre- Paleozoic evolution of the NQOB. The complex, which consists of metagraywackes and marbles, un- derwent regional amphibolite-facies metamorphism. In this study, we constrained the formation age of the Qinling Complex to the period between the late Mesoproterozoic and the early Neoproterozoic （ca. 1062-962 Ma）, rather than the Paleoproterozoic as previously thought. The LA-ICP-MS data show two major metamorphic ages （ca. 499 and ca. 420-400 Ma） for the Qinling Complex. The former age is consistent with the peak metamorphic age of the high- and ultra-high pressure （HP-UHP） rocks in the Qinling Complex, indicating that both the HP-UHP rocks and their country rocks experienced intensive regional metamorphism during the Ordovician. The latter age may constrain the time of partial melting in the NQOB between the late Silurian and early Devonian. The Qinling Complex is mostly affiliated with subduction-accretion processes along an active continental margin, and should contain detritus deposited in a forearc basin.     

Cenozoic Exhumation History of the East Kunlun Orogenic Belt Constrained by Apatite Fission‐Track Thermochronology

正Objective The East Kunlun Orogenic belt constitutes the first marked change in the topographic reliefs north of the Qinghai-Tibet Plateau.The Cenozoic tectonic evolution of this orogenic belt is crucial for understanding the remote deformational effects of the Eurasian plate collision and the migration track at the northern margin of the plateau.However,when and how the uplift occurred remains