Three global tectonic systems that formed since the middle Jurassic (160Ma ago)are outlined based on the global map of the Cenozoic and Mesozoic tectonics edited by Ma Zongjin et al.(1996).They are the circum\|Pacific...Three global tectonic systems that formed since the middle Jurassic (160Ma ago)are outlined based on the global map of the Cenozoic and Mesozoic tectonics edited by Ma Zongjin et al.(1996).They are the circum\|Pacific tectonic system,the mid\|ocean ridge tectonic system and the intra\|continental tectonic system of the north hemisphere.The map shows that about 80% of the total length of the continental orogens are concentrate on the north hemisphere of the earth,of which a latitudinal mountain\|plateau chain occur within a zone between north latitude 20°and 50°.Seismic and volcanic activities demonstrate that the intracontinental tectonic system on the north hemisphere is still active.Whilst distribution of the continental deep\|focus earthquakes and almost ultra high\|pressure rock found so far over the World,that are assumed both related to recent or previous deep subduction of continent,along with this zone.The latitudinal mountain\|plateau chain is subdivided into four active tectonic region of Qinghai—Xizang(Tibet),Iranian,eastern mediterranean and North American,both characterized by an individual similar mountain\|plateau\|basin structure with major active boundaries or controlling faults (Fig.1).These active regions are all close to primary dynamic boundaries of continent\|continent collision.Solution of source mechanisms shows that regional tectonic stress field in these regions are dominated by a nearly NS or NNE—SSW direction compression corresponding to a local plate motions and a global compressive zone.Correlation between the formation of the continental latitudinal mountain\|plateau chain on north hemisphere and the oceanic plate tectonics is discussed using the information of the “Map of Magnetic Lineations of the World’s Ocean Basins (Cande et al.,1989)”and the Cenozoic and Mesozoic tectonic evolution in the continents.Total 49 accretion units formed during 6 accretion stages of the ocean spreading in three chief oceans (the Pacific,the India and the Atlantic)si nce 160Ma ago,are subdivided.The distinguished oceanic accretion tectonics in combination with the geometrical and kinematics data of adjust continental f ragments allowed outline of the development of the continental latitudinal tecto nic zone of north hemisphere.Whilst,two global asymmetrical geodynamic systems of north\|south an east\|west direction,that may be composed of meridional conve ction,latitudinal convection and inertial flow resulting from the variation of the Earth’s rotational velocity,are used to discuss on the two global geodynamic systems in which the intracontinental latitudinal tectonic zone developed.展开更多
Gangdise tectonic belt, located in the middle part of Tibet—Qinghai plateau Tethys tectonic domain, is the most representative region in Tibet—Qinghai plateau Tethyan evolution especially in Mesozoic era. It is main...Gangdise tectonic belt, located in the middle part of Tibet—Qinghai plateau Tethys tectonic domain, is the most representative region in Tibet—Qinghai plateau Tethyan evolution especially in Mesozoic era. It is mainly covered by thick Jurassic—Cretaceous system layer. During the Mesozoic to Cenozoic era, strong island\|arc types volcanism and volcanic rocks and intrusive rocks belt.. Geologists had divided the Tibet Tethyan evolution into three or four stages (Huang, Jiqing, 1987; Pan Guitang, Li Xinzheng, 1993), according to the ocean\|land conversion process of Tethyan evolution .The Tethyan evolution and the nature of Gangdise tectonic belt had been well\|studied by geologists (Huang Jiqing, 1987; Deng Wanming, 1984; Xia Daixiang, 1986; Cheng Changlun 1987; ZhouXiang 1993; Pan Guitang, 1996). Studies showed that Gangdise tectonic belt, from upper Paleozoic to Mesozoic era, had been developed alternate multiple island arc\|basin system, and characterized by many basin types and strong tectonic\|magma activity. Based on the study of Gangdise multiple island arc\|basin system, I present another version of Gangdise tectonic belt tectonic units division and evolution here.展开更多
Recently, this study group established “the map of MOHO\|surface bathymetric line in Chinese and Near Region" on the basis of latest survey and study of the crustal depth, the preliminary result shows that the r...Recently, this study group established “the map of MOHO\|surface bathymetric line in Chinese and Near Region" on the basis of latest survey and study of the crustal depth, the preliminary result shows that the regular meridional and latitudinal upwarping and downwarping structural pattern of MOHO\|surface bathymetric line among Eurasian plate and Pacific plate and the Indian plate alternately appears, and which is accreted and coupled with basin ridge structure that exist shallow crustal base, continental crust and oceanic crust and others regular upwarping and downwarping net structure system that possessing different block characters and different scales exist together. Among different structure systems, it occurs that ramp downwarping impetus transform structure belts whose trends is characteristic. Nowadays upwarping and downwarping net structure system is basically modeled in Himalayan orogeny period. It is showed that the Earth revolution way has been changed in this period, which leaded to a new Earth dynamics cycle.The pattern of upwarping and downwarping structure among different structure systems or different structure blocks , and the characters of different trends and different scale transform structure belts, reflects the structure movement way and their conversion law, and reveals the Earth centralized dynamics mechanics that is produced by the revolutionary effect under the environments of aster system. This can be clearly reflected by the change of impetus way between Qinghai—Tibet highland structure system and near structure system.展开更多
The Altun faulted Zone has been focused by lots of geologists for many years because it lies in a boundary area of several main tectonic units in the western China and is a geographically northern boundary line of Tib...The Altun faulted Zone has been focused by lots of geologists for many years because it lies in a boundary area of several main tectonic units in the western China and is a geographically northern boundary line of Tibet plateau.The latest achievements show that the Altun faulted zone is not only a Cenozoic strike\|slip faulted system but also an orogenic zone which underwent mutually subduction\|collision among paleo\|plates (or terrains) in its early stage and consists of geological bodies of different ages and tectonic environments. Based on the results of geological characteristics,petrology, geochemistry and isotopic dating, the Altun Orogenic Zone can be divided into four tectonic units and is considered to have undergone five stages during its tectonic evolution.The four tectonics units are :(1) Abei metamorphic block, which consists of Archean metamorphic complex of granulite facies;.(2) Hongliugou—Lapeiquan tectonic melange belt, which is composed of ophiolite blocks(belt), OIB blocks, pelagic silicalite, shallow\|bathyal sedimentary rock blocks and high\|pressure metamorphi c rock blocks. (3) Milanhe—Jinyanshan island\|arc block, which consists of mid\|uplifting belt and the south and north active margins. The uplifting belt is composed of metasandstone, marble, overlying thick stromatolite (Jinyanshan Group of Jixian System). Metamorphic rocks of 450Ma occur in both south and north hactive margin. Post\|collision bimodal volcanic rocks and A\|type granite occur in the middle and the north side.(4) Apa—Mangya tectonic melange belt, which consists of ophiolite(including ultramafic rocks, gabbro, plagiogranite and basalt) and flysch and eclogite of late Ordovician.展开更多
Recently, the Altyn strike\|slip fault in western China has become a hot topic to the research on continental dynamics of Tibetan Plateau. The chronological research is very important to constrain the age of tectono\|...Recently, the Altyn strike\|slip fault in western China has become a hot topic to the research on continental dynamics of Tibetan Plateau. The chronological research is very important to constrain the age of tectono\|thermal event within Altyn fault belt. Many isotopic dating researches, related to the ophiolites, high\|pressure metamorphic rocks and some granitic rocks, have been done by Chinese and foreign geologists in the area. There, however, are only few isotopic dating researches on the syntectonic\|growing minerals within Altyn fault. We collected a sample of Caledonian mylonitized granite (At3a) in the north of Dangjin pass and two samples of Jurassic meta\|sedimentary rocks in Qaidam gate fault\|valley (At37c) and Geshi fault\|valley (At30d). All the samples contain the syntectonic\|growing minerals such as white mica, chlorite, sericite and biotite etc. By dating these minerals, we can constrain the time of the tectonic events occurred in Altyn fault belt.Sample At3a, mylonitized granite, has been strongly deformed with undulating extinction of quartz. The plagioclase and quartz were elongated and surrounded by fine\|grained white micas and chlorites with strain shadow texture. These suggest that the sample has been suffered ductile deformation. The estimation of p\|T condition is 350℃, 180MPa. The isochronal age of (89.2±1.6)Ma has been obtained by laser probe 40 Ar/ 39 Ar dating analyses of six white mica grains.展开更多
Distinguishing geochemical anomalies from background is a basic task in exploratory geochemistry. The derivation of geochemical anomalies from stream sediment geochemical data and the decomposition of these anomalies ...Distinguishing geochemical anomalies from background is a basic task in exploratory geochemistry. The derivation of geochemical anomalies from stream sediment geochemical data and the decomposition of these anomalies into their component patterns were described. A set of stream sediment geochemical data was obtained for 1 880 km 2 of the Pangxidong area, which is in the southern part of the recently recognized Qinzhou-Hangzhou joint tectonic belt. This belt crosses southern China and tends to the northwest (NE) direction. The total number of collected samples was 7 236, and the concentrations of Ag, Au, Cu, As, Pb and Zn were measured for each sample. The spatial combination distribution law of geochemical elements and principal component analysis (PCA) were used to construct combination models for the identification of combinations of geochemical anomalies. Spectrum-area (S-A) fractal modeling was used to strengthen weak anomalies and separate them from the background. Composite anomaly modeling was combined with fractal filtering techniques to process and analyze the geochemical data. The raster maps of Au, Ag, Cu, As, Pb and Zn were obtained by the multifractal inverse distance weighted (MIDW) method. PCA was used to combine the Au, Ag, Cu, As, Pb, and Zn concentration values. The S-A fractal method was used to decompose the first component pattern achieved by the PCA. The results show that combination anomalies from a combination of variables coincide with the known mineralization of the study area. Although the combination anomalies cannot reflect local anomalies closely enough, high-anomaly areas indicate good sites for further exploration for unknown deposits. On this basis, anomaly and background separation from combination anomalies using fractal filtering techniques can provide guidance for later work.展开更多
The distribution of the Mountain ranges, Plateau as well as the distribution of continents and oceans on the earth’s surface are the embodies of the structure and heat states of the materials at the deep crust and of...The distribution of the Mountain ranges, Plateau as well as the distribution of continents and oceans on the earth’s surface are the embodies of the structure and heat states of the materials at the deep crust and of the tectonic stress of regions. There should be a prevalent corresponding between terrestrial height and the texture, thermal and stress states of lithosphere. However, there is no a general consensus on what extent different factors affecting the height of a terrain should be up to now, and this is very apparent for the models of plateau uplifting.1\ Debates on the compensatory depth of crustal equilibrium\;Based on a previous equilibrium model, Woollard(1969) set up an equation to show the relation among the crustal thickness ( D \-m), the depth of Mohorovicic discontinuity(M)and height above sea level( H):D \-m=33.2+8.5 H (km). By this equation it is implied that equilibrium compensation has been reached at the depth of Mohorovicic discontinuity for the height of a terrain. As Woollard (1970)described, there is no evidence to show that mass distribution beneath the Mohorovicic discontinuity ever played an important roles in the equilibrium compensation of the crust.展开更多
In NW Himalayas, the suture zone between the collided Indian and the Karakoram plates is occupied by crust of the Cretaceous Kohistan Island\|Arc Terrane [1] . Late Cretaceous (about 90Ma) accretion with the southern ...In NW Himalayas, the suture zone between the collided Indian and the Karakoram plates is occupied by crust of the Cretaceous Kohistan Island\|Arc Terrane [1] . Late Cretaceous (about 90Ma) accretion with the southern margin of the Karakoram Plate at the site of the Shyok Suture Zone turned Kohistan to become an Andean\|type margin. The Neotethys was completely subducted at the southern margin of Kohistan by Early Tertiary, leading to collision between Kohistan and continental crust of the Indian plate at the site of the Main mantle thrust.More than 80% of the Kohistan terrane comprises plutonic rocks of (1) ultramafic to gabbroic composition forming the basal crust of the intra\|oceanic stage of the island arc, and (2) tonalite\|granodiorite\|granite composition belong to the Kohistan Batholith occupying much of the intermediate to shallow crust of the terrane mostly intruded in the Andean\|type margin stage [2] . Both these stages of subduction\|related magmatism were associated with volcanic and sedimentary rocks formed in Late Cretaceous and Early Tertiary basins. This study addresses tectonic configuration of Early Tertiary Drosh basin exposed in NW parts of the Kohistan terrane, immediately to the south of the Shyok Suture Zone.展开更多
A detailed survey of 40 Ar/ 39 Ar dating was carried out on basement rocks of the Eastern Kunlun Mountains. The samples were collected from Jinshuikou, Kuhai, Xiaomiao, Wanbaogou and Nachitai groups. All the samples w...A detailed survey of 40 Ar/ 39 Ar dating was carried out on basement rocks of the Eastern Kunlun Mountains. The samples were collected from Jinshuikou, Kuhai, Xiaomiao, Wanbaogou and Nachitai groups. All the samples were analysed in 40 Ar/ 39 Ar isotopic dating laboratory of Salzburg University in Austria. The results of 40 Ar/ 39 Ar dating include: (1) The Jinshuikou Group shows hornblende age of 388 5Ma, muscovite at 233～227Ma, and biotite ages between 232 2 and 208 2Ma. These are interpreted to result from amphibolite\|grade Caledonian orogenic diastrophism and low\|grade metamorphic Indosinian overprint. (2) The Xiaomiao Group is characterized by a 40 Ar/ 39 Ar muscovite age of 413 8Ma. (3) The Wanbaogou Group gives out a muscovite age of ca. 160Ma to the S of the Central Kunlun fault. (4) The Nachitai Group revealed a biotite age of ca. 110Ma that was overprinted by a very\|low\|grade event at 60～40 Ma. (5) The Kuhai basement to the S of the Central Kunlun fault is again characterized by a Caledonian age without detectable late overprint: Hornblende: ca. 405Ma, muscovite 376～357Ma, biotite: ca. 360Ma. The new ages constrain that the Kunlun basement essentially formed during Caledonian tectonic events. The basement was locally overprinted by Indosinian tecto\|thermal event in the north of the Central Kunlun fault, and by Jurassic and Paleogene tecto\|thermal events in the south of the Central Kunlun fault.展开更多
Qilian orogenic belt is a typical orogenic belt formed by polycyclic collisions between the North China plate and Qaidam microplate. Qilian ocean originated from the rift of the late Proterozoic Rodinia continent(Pang...Qilian orogenic belt is a typical orogenic belt formed by polycyclic collisions between the North China plate and Qaidam microplate. Qilian ocean originated from the rift of the late Proterozoic Rodinia continent(Pangea\|850), evolved through rift basin and became an archipelagic ocean in the Caledonian stage. The Lower Proterozoic strata in Qilian area are mid\|high\|rank metamorphic rocks that constitute the metamorphic basement of the area. The “Huangyuan Movement" (in South Qilian and Central Qilian) and "Alashan Movement" (in North Qilian) in the latest Late Proterozoic formed a regional unconformity. The middle Proterozoic in the area are mudstones and carbonate rocks with stromatolites and ooids. The Qingbaikou System of the upper Proterozoic in the North Qilian and Corridor region is also mudstone and carbonate rock with stromatolites. The Qingbaikou System in Central Qilian is sandstones and mudstones. There are alkaline and tholeiite in the Sinian System in North Qilian and Corridor. The contact between Qingbaikou System and Sinian System is a regional unconformity (Quanji Movement). Qilian ocean began to rift away in Caledonian tectonic stage on the Pre\|Sinian basement.展开更多
In accordance with the studies concerning the tectonics of Nei Monggolmade by Huang Jiqing and others, two tectonic units occur in this area:Sino-Korean Platform to the south and Nei Monggol-Greater Khingan Mtsfold sy...In accordance with the studies concerning the tectonics of Nei Monggolmade by Huang Jiqing and others, two tectonic units occur in this area:Sino-Korean Platform to the south and Nei Monggol-Greater Khingan Mtsfold system to the north. The dividing line between the two units lies fromBaiyun’ebo on the west to Chifeng on the east. Geophysical studies demonst-rate that there are two gravity gradient zones trending ENE in the northernmargin of the North China Platform. The northern zone is a linear anomalyzone of--50 to--45 mGal extending from Baiyun’ebo in the west to theeast of Chifeng. The southern zone, 60--70km wide, lies from Guyang throughJining to Longhua in the east and its amplitude of gravity gradient amountsto 60 mGal. Field geological survey indicates that there are two main faultedzones. Our recent investigations suggests that there are two Proterozoic riftsof E-W trend in the northern margin of the North China Platform.展开更多
The Late Cenozoic fold\|and\|thrust zone along the northwestern margin of the Tarim Basin and the adjacent Tian Shan of Central Asia is an actively deforming part of the India\|Asia collision system. This deformation ...The Late Cenozoic fold\|and\|thrust zone along the northwestern margin of the Tarim Basin and the adjacent Tian Shan of Central Asia is an actively deforming part of the India\|Asia collision system. This deformation zone has two remarkable oppositely vergence arcuate fold\|and\|thrust systems (Kepingtage and Kashi\|Atushi fold\|and\|thrust belts) reaching from east of Keping to west of Kashi. This shape is manifested by structure, topography and seismicity. From north to south, this deformation zone is characterized by four main kinematic elements: (1) a hanging\|wall block (Maidan fault and Tuotegongbaizi\|Muziduke thrust system) that represents the Cenozoic reactivation of a late Paleozoic thrust system; (2) an imbricated thrust stack (Kepingtage\|Tashipeshake thrust system) where slices of Tarim platform sediments are thrust south toward the basin; (3) the Kashi\|Atushi fold\|and\|thrust system where thrusting and folding verge toward the Tian Shan; (4) a foot\|wall block (Tarim craton) that dips gently northwest below the sediment\|filled southern Tian Shan basin and generally has little internal deformation.展开更多
The tectonic deformation image of Asia Continent can be explained successfully by the model of collision between India secondary continent and Euro\|Asia Plate (P. Molnar and P.Tapponnier, 1975). This paper mainly dis...The tectonic deformation image of Asia Continent can be explained successfully by the model of collision between India secondary continent and Euro\|Asia Plate (P. Molnar and P.Tapponnier, 1975). This paper mainly discusses the characteristics of tectonic deformation and strong earthquake activities on the east border of Tibet Plateau.1\ Characteristics of tectonic deformation on the east border of Tibet Plateau\;Controlled by the flow of the plateau crust material, the movement of the east border of Tibet plateau is mainly horizontal so as to produce two slipping\|block: one results from the slide out of Chuandian Rhombus Block along the SSE direction, the other results from the lateral extrusion of Chuanqing Block with the SEE direction. The slip rate of the north part of Chuandian Rhombus Block, the west region of Sichuan, is 5～8mm/a;2～3mm/a on the south part (the center part of Yunan); the slip rate of Chuanqing is 3～5mm/a and <1mm/a on Longmenshan region (Tang Rongchang, 1993). The slipping features of the blocks directly decide the movement characters of different fault systems: the uniform sinistral shear movement on the east boundary fault of Chuandian Rhombus Block, from the geological viewpoint, the average horizontal slip rate is about 10mm/a, and 5～8mm/a on the Anninghe, Zemuhe and Xiaojiang faults. The dextral shear movement can be found on the west boundary faults composed by Jinshajiang and Honghe faults. Located at the dextral diagonal region between Honghe and Zhongdian faults, the northwestern region of Yunnan shows a tensile stress field with near EW direction and large graben valleys with near NS direction on the ground due to the dextral slip movements of these two faults and slip of Chuandian Rhombus Block along the SSE direction. The normal features of extension tectonic deformation region can be found in this region. Some inner faults (such as Amaniqing, Xiqinglingbeilu) of Chuanqing block show the character of sinistral shear movement with some components of normal slip movement. As the east boundary of Tibet plateau, Minshan and Longmenshan Mountains form the east wall of the plateau. Contrasting to the moving direction of Chuanqing block, the transition from horizontal movement to vertical movement produced the huge nappe reverse deformation in this region, and formed some front\|Mount compensating press\|sag basins such as Gonggaling, Zhangla and Chengdu. Because of the diversity of slip rate of different boundary faults, some clockwise rotating movement can be found in different sub\|blocks.展开更多
New results from deep seismic sounding reveal that the Tarim block (basin) was subducted, with gently dipping, to the W.Kunlun Mts. The depths of Moho from north to south are 50km in S.Tarim to 65km in the W. Kunlun M...New results from deep seismic sounding reveal that the Tarim block (basin) was subducted, with gently dipping, to the W.Kunlun Mts. The depths of Moho from north to south are 50km in S.Tarim to 65km in the W. Kunlun Mts. A low velocity and low resistivity layer occurs at the depth of 15～30km, which may be the decollement in the upper crust. A “delamination Crack" might have been formed in the lower crust\|mantle lid, causing the intrusion of alkaline magma along the southern margin of the W. Kunlun Mts. A detailed research for forming and evolving of the Kudi ophiolite in the central part of the W. Kunlun Mts.,which has been given the age of 700～450Ma by using the Re\|Os isotopic dating, and the Radiolarits in chert intercalated with pillow lava are determined to be the late Ordovician to Silurian. Until now we did not find any complete ophiolite suite except Kudi ophiolite. So we suggest that there was no “vast protero\|ocean", and a “limited oceanic basin" exists only during the late Proterozoic to Early Paleozoic, which might have been subducted in Silurian\|Devonian and formed the oldest suture in the north of the Tibet plateau.A suture zone consisting of H. P/T metamorphic blueschist, ophiolitic melange and olistostrome in the north\|western Tibet has been revealed recently, which may extend to NW. connecting with MKT in N. Pakistan.A study of the Fission track thermochronology indicates that the W.Kunlun Mts. has been undergone a pulsatory uplift since 20～18Ma,and a rapid uplift after 3Ma.A model of collision between the Indo\|Pakistan subcontinent\|N.Tibet and the Eurasian blocks of Tarim has been illustrated.展开更多
The synorogenic sediments in the foreland basins preserve a potential record of varied depositional environments that respond to and are largely controlled by tectonic events of the mountain along the basin margin. In...The synorogenic sediments in the foreland basins preserve a potential record of varied depositional environments that respond to and are largely controlled by tectonic events of the mountain along the basin margin. In the exploration of the uplift process of the Qinghai—Tibet Plateau, research on the foreland basins around the plateau is of vital significance. Much work have been carried out on the southern margin along the Himalayas and on the eastern margin, however, seldom work was reported along the northern boundary of the plateau, this have blocked the generation of an integrative image of the evolution of the entire plateau. The Gansu Corridor, located on the northeast margin of the Qinghai—Tibet Plateau, is a Cenozoic foreland basin system formed due to the northward overthrust and overload of the plateau. Thousand of meters detrital sediments derived mainly from denudation of the Qilian orogen have deposited in the basin since Oligocene. Here we report a detailed lithologic and magnetostratigraphic work carried out on the late Cenozoic sedimentary sequences in the Jiuxi Basin, western Gansu Corridor, to investigate the neotectonism of the western Qilian Mt.展开更多
Deformation during the uplift of Pamir Since the Himalayan movement, the Punjab block of Indian plate has intruded into the interior of Eurasian plate, produced a protrusive Pamir knot in eastern Tethys. The Pamir kno...Deformation during the uplift of Pamir Since the Himalayan movement, the Punjab block of Indian plate has intruded into the interior of Eurasian plate, produced a protrusive Pamir knot in eastern Tethys. The Pamir knot is where crustal shortening is most intensive in Tethys. After India\|Eurasia collision, giant relief resulted from fast uplifting of Karakorum due to the convergence and underplating in northern and southern margins of Karakorum, the uplifting rates changed with times, and thrusting would be one of the most important factors controlling the uplifting. At the same time, large scale strike\|slip faulting could produced large vertical offsets, so that the exhumation of the rocks from middle and lower crust has drawn much attention. The post\|collisional deformation and evolution of Karakorum would involve the processes of continental escape, crustal shortening and thickening, and orogenic collapse in extensional regime. The thrusting started in late Jurassic and early Cretaceous, but two peaks occurred in late Cretaceous and Eocene, respectively. A large amount of klippen produced by thrusting from north to south have been discovered in the northern slope of the Kungai in front of Pamir. Molnar and Tapponnier noted that the mount of crustal shortening in Pamir would be up to 2000km in the past 40～45Ma, and Coward proposed that 300～400km shortening has happened only in southern Pamir to northern Pakistan. In western Pamir from Kabul of Afghanistan to Quatta of Pakistan, the Chaman left\|lateral strike\|slip fault system extends 1000km long. Multiple structural superposition in eastern Pamir, due to the effects of the uplifting of Qinghai\|Tibet plateau, resulted in complex deformation patterns.展开更多
From the planktonic foraminiferal and nannofossil events across the Oligocene/Miocene boundary (OMB) to the major transient glaciation at this epoch boundary,Mi-l,the paleoclimate,stratigraphic and paleontologic event...From the planktonic foraminiferal and nannofossil events across the Oligocene/Miocene boundary (OMB) to the major transient glaciation at this epoch boundary,Mi-l,the paleoclimate,stratigraphic and paleontologic events showed a prominent change across the OMB.However,the previous work was mainly about the marine deposits,especially the ocean drilling data.Whatever,the continental strata,such as the alluvial and lacustrine sedimentation in展开更多
River evolution at margins of the Tibetan Plateau may provide valuable information for understanding climatic change and tectonic movement of the past. Here we focus on the Huangshui River,a tributary of the Yellow Ri...River evolution at margins of the Tibetan Plateau may provide valuable information for understanding climatic change and tectonic movement of the past. Here we focus on the Huangshui River,a tributary of the Yellow River,crossing a series of tectonically subsided and uplifted areas that show diversity patterns of terrace formation.The distribution of fluvial terrace is studied by mapping and dating.Three terraces in Haiyan basin,four terraces in Huangyuan basin,19 terraces in Xi’ning basin,nine terraces in Ping’an basin,five terraces in Ledu basin and 12 terraces in Minhe basin are recognized.Magne-展开更多
The plate tectonic model constructed by R.H. Sillitoe for the origin of porphyry copper deposits said that porphyry copper deposits were associated with convergent plate boundaries and compressional tectonic settings....The plate tectonic model constructed by R.H. Sillitoe for the origin of porphyry copper deposits said that porphyry copper deposits were associated with convergent plate boundaries and compressional tectonic settings. They were formed along destructive plate margins above subduction zones of oceanic crust. Although this model is suitable for most porphyry copper deposits because the main porphyry copper deposit belts accord with the main Mesozoic or Cenozoic plate subduction zones in space and time in the world, it is difficult to use Sillitoe’s model for explaining the formation of some intracontinental porphyry deposits such as Yulong, the largest one in East Tibet.Having no relation with a subduction zone of plates, Yulong porphyry copper deposit was formed in an intracontinental extensional tectonic setting. Qamdo block, in which Yulong lies, was a small massif in East Tibet. With its Proterozoic crystalline basement and Lower Paleozoic folded basement, Qamdo block had experienced relative stable geologic evolution and a cover more than 20000m in thickness mainly composed of clastic rock and carbonate formed from Devonian to Cretaceous. During this time, although two small oceanic basins(Jinshajiang basin and Lancangjiang basin) between which Qamdo block lay developed and subducted and relevant island arc belts occured along the east and west margins of the block, all of them were closed before Later Triassic. In Cenozoic, mainly from 52 to 35Ma, influenced by the intracontinental convergence of the three large plates(India to the southwest, Tarim to the northwest,and Yangtze to the east), Qamdo block and its surrounding areas (East Tibet) which were just to the west of Yangtze plate were in an intracontinental pull\|apart situation induced by the sinistral strike\|slip fault system while most Himalaya—Kunlun—Tibet areas between India and Tarim plates were in a compression state by the SN\|trending tectonic stress. Controlled by the regional strike\|slip fault systems, the calc\|alkaline magma deriving from the upper mantle or lower crust ascended, occurring porphyry copper mineralization in the relative uplift areas. At the same time, in the relative depression areas, also controlled by the regional deep strike\|slip faults which might cut the lithosphere, several linear or rhombic pull\|apart red molasse basins such as Gongjoe, Nangqen, parallel to the porphyry belt, were formed in this region.展开更多
The Tarim basin, located in the northern margin of Tibet, plays a key role in comprehending Tibetan plateau rapid uplift process. Focuses have been on the contribution of basin block to create high mountain (e.g.,Chen...The Tarim basin, located in the northern margin of Tibet, plays a key role in comprehending Tibetan plateau rapid uplift process. Focuses have been on the contribution of basin block to create high mountain (e.g.,Chen and Molnar,1977, Molnar et al.,1993, Ph. Matte, Tapponnier et al.,1996) since 1970. The models, which mainly depend on result of geological survey and other geophysical observation in the region excepted Deep Seismic Sounding, remained unsure because of blank(or absence ) of DSS data until our experiment was performed. How Tarim and west Kunlun to contact in depth ? What different is in crust structure between Tarim and west Kunlun Mt.? This is what we will reply to in our program.We finished the program in 1997. A total of 120 set seismograms (with 3\|component sensors) and 18000kg (AT and TNT) dynamos were used for the DSS field project. 6 shot in Tarim basin and 1 shot in west Kunlun Mt. (Quanshuigou) had been shoot successfully. One shot (Pishan shot) is used as fan\|shape observation (offset is from 150km to 220km) in 6 shots located in Tarim basin. The survey line is along Hotan river across the Tarim basin from the north to the south. In particular, we carried 20 set seismic recorders to Kunlun Mt. to make a short line about 60 km as the southern tendency of our line. The seismic recorders were placed in an interval of 3km from one stations to the next and covered a distance of more than 300km. The stations have to be moved their location per 2\|shotting to form a meeting system or a tracing system (layout). Fig.1 showed our survey line and location of shot as well as recorder stations. Finally we gained 625 cassettes with original seismic record (include cassettes of shooting time recorder et al.). After data process total 1147 quite high\|quality three\|component digital records have been used to analyze. Here, only results of analyzing P wave data is given.展开更多
文摘Three global tectonic systems that formed since the middle Jurassic (160Ma ago)are outlined based on the global map of the Cenozoic and Mesozoic tectonics edited by Ma Zongjin et al.(1996).They are the circum\|Pacific tectonic system,the mid\|ocean ridge tectonic system and the intra\|continental tectonic system of the north hemisphere.The map shows that about 80% of the total length of the continental orogens are concentrate on the north hemisphere of the earth,of which a latitudinal mountain\|plateau chain occur within a zone between north latitude 20°and 50°.Seismic and volcanic activities demonstrate that the intracontinental tectonic system on the north hemisphere is still active.Whilst distribution of the continental deep\|focus earthquakes and almost ultra high\|pressure rock found so far over the World,that are assumed both related to recent or previous deep subduction of continent,along with this zone.The latitudinal mountain\|plateau chain is subdivided into four active tectonic region of Qinghai—Xizang(Tibet),Iranian,eastern mediterranean and North American,both characterized by an individual similar mountain\|plateau\|basin structure with major active boundaries or controlling faults (Fig.1).These active regions are all close to primary dynamic boundaries of continent\|continent collision.Solution of source mechanisms shows that regional tectonic stress field in these regions are dominated by a nearly NS or NNE—SSW direction compression corresponding to a local plate motions and a global compressive zone.Correlation between the formation of the continental latitudinal mountain\|plateau chain on north hemisphere and the oceanic plate tectonics is discussed using the information of the “Map of Magnetic Lineations of the World’s Ocean Basins (Cande et al.,1989)”and the Cenozoic and Mesozoic tectonic evolution in the continents.Total 49 accretion units formed during 6 accretion stages of the ocean spreading in three chief oceans (the Pacific,the India and the Atlantic)si nce 160Ma ago,are subdivided.The distinguished oceanic accretion tectonics in combination with the geometrical and kinematics data of adjust continental f ragments allowed outline of the development of the continental latitudinal tecto nic zone of north hemisphere.Whilst,two global asymmetrical geodynamic systems of north\|south an east\|west direction,that may be composed of meridional conve ction,latitudinal convection and inertial flow resulting from the variation of the Earth’s rotational velocity,are used to discuss on the two global geodynamic systems in which the intracontinental latitudinal tectonic zone developed.
文摘Gangdise tectonic belt, located in the middle part of Tibet—Qinghai plateau Tethys tectonic domain, is the most representative region in Tibet—Qinghai plateau Tethyan evolution especially in Mesozoic era. It is mainly covered by thick Jurassic—Cretaceous system layer. During the Mesozoic to Cenozoic era, strong island\|arc types volcanism and volcanic rocks and intrusive rocks belt.. Geologists had divided the Tibet Tethyan evolution into three or four stages (Huang, Jiqing, 1987; Pan Guitang, Li Xinzheng, 1993), according to the ocean\|land conversion process of Tethyan evolution .The Tethyan evolution and the nature of Gangdise tectonic belt had been well\|studied by geologists (Huang Jiqing, 1987; Deng Wanming, 1984; Xia Daixiang, 1986; Cheng Changlun 1987; ZhouXiang 1993; Pan Guitang, 1996). Studies showed that Gangdise tectonic belt, from upper Paleozoic to Mesozoic era, had been developed alternate multiple island arc\|basin system, and characterized by many basin types and strong tectonic\|magma activity. Based on the study of Gangdise multiple island arc\|basin system, I present another version of Gangdise tectonic belt tectonic units division and evolution here.
文摘Recently, this study group established “the map of MOHO\|surface bathymetric line in Chinese and Near Region" on the basis of latest survey and study of the crustal depth, the preliminary result shows that the regular meridional and latitudinal upwarping and downwarping structural pattern of MOHO\|surface bathymetric line among Eurasian plate and Pacific plate and the Indian plate alternately appears, and which is accreted and coupled with basin ridge structure that exist shallow crustal base, continental crust and oceanic crust and others regular upwarping and downwarping net structure system that possessing different block characters and different scales exist together. Among different structure systems, it occurs that ramp downwarping impetus transform structure belts whose trends is characteristic. Nowadays upwarping and downwarping net structure system is basically modeled in Himalayan orogeny period. It is showed that the Earth revolution way has been changed in this period, which leaded to a new Earth dynamics cycle.The pattern of upwarping and downwarping structure among different structure systems or different structure blocks , and the characters of different trends and different scale transform structure belts, reflects the structure movement way and their conversion law, and reveals the Earth centralized dynamics mechanics that is produced by the revolutionary effect under the environments of aster system. This can be clearly reflected by the change of impetus way between Qinghai—Tibet highland structure system and near structure system.
文摘The Altun faulted Zone has been focused by lots of geologists for many years because it lies in a boundary area of several main tectonic units in the western China and is a geographically northern boundary line of Tibet plateau.The latest achievements show that the Altun faulted zone is not only a Cenozoic strike\|slip faulted system but also an orogenic zone which underwent mutually subduction\|collision among paleo\|plates (or terrains) in its early stage and consists of geological bodies of different ages and tectonic environments. Based on the results of geological characteristics,petrology, geochemistry and isotopic dating, the Altun Orogenic Zone can be divided into four tectonic units and is considered to have undergone five stages during its tectonic evolution.The four tectonics units are :(1) Abei metamorphic block, which consists of Archean metamorphic complex of granulite facies;.(2) Hongliugou—Lapeiquan tectonic melange belt, which is composed of ophiolite blocks(belt), OIB blocks, pelagic silicalite, shallow\|bathyal sedimentary rock blocks and high\|pressure metamorphi c rock blocks. (3) Milanhe—Jinyanshan island\|arc block, which consists of mid\|uplifting belt and the south and north active margins. The uplifting belt is composed of metasandstone, marble, overlying thick stromatolite (Jinyanshan Group of Jixian System). Metamorphic rocks of 450Ma occur in both south and north hactive margin. Post\|collision bimodal volcanic rocks and A\|type granite occur in the middle and the north side.(4) Apa—Mangya tectonic melange belt, which consists of ophiolite(including ultramafic rocks, gabbro, plagiogranite and basalt) and flysch and eclogite of late Ordovician.
基金theNationalNaturalScienceFundCommittee (NO .4 9772 157)
文摘Recently, the Altyn strike\|slip fault in western China has become a hot topic to the research on continental dynamics of Tibetan Plateau. The chronological research is very important to constrain the age of tectono\|thermal event within Altyn fault belt. Many isotopic dating researches, related to the ophiolites, high\|pressure metamorphic rocks and some granitic rocks, have been done by Chinese and foreign geologists in the area. There, however, are only few isotopic dating researches on the syntectonic\|growing minerals within Altyn fault. We collected a sample of Caledonian mylonitized granite (At3a) in the north of Dangjin pass and two samples of Jurassic meta\|sedimentary rocks in Qaidam gate fault\|valley (At37c) and Geshi fault\|valley (At30d). All the samples contain the syntectonic\|growing minerals such as white mica, chlorite, sericite and biotite etc. By dating these minerals, we can constrain the time of the tectonic events occurred in Altyn fault belt.Sample At3a, mylonitized granite, has been strongly deformed with undulating extinction of quartz. The plagioclase and quartz were elongated and surrounded by fine\|grained white micas and chlorites with strain shadow texture. These suggest that the sample has been suffered ductile deformation. The estimation of p\|T condition is 350℃, 180MPa. The isochronal age of (89.2±1.6)Ma has been obtained by laser probe 40 Ar/ 39 Ar dating analyses of six white mica grains.
基金Project(1212010071012) supported by Guangdong Pangxidong Mineral Prospect Investigation, ChinaProject(41004051) supported by the National Natural Science Foundation of ChinaProject ([2007]038-01-18) supported by Nationwide Mineral Resource Potential Evaluation Projects of Ministry of Land and Resources, China
文摘Distinguishing geochemical anomalies from background is a basic task in exploratory geochemistry. The derivation of geochemical anomalies from stream sediment geochemical data and the decomposition of these anomalies into their component patterns were described. A set of stream sediment geochemical data was obtained for 1 880 km 2 of the Pangxidong area, which is in the southern part of the recently recognized Qinzhou-Hangzhou joint tectonic belt. This belt crosses southern China and tends to the northwest (NE) direction. The total number of collected samples was 7 236, and the concentrations of Ag, Au, Cu, As, Pb and Zn were measured for each sample. The spatial combination distribution law of geochemical elements and principal component analysis (PCA) were used to construct combination models for the identification of combinations of geochemical anomalies. Spectrum-area (S-A) fractal modeling was used to strengthen weak anomalies and separate them from the background. Composite anomaly modeling was combined with fractal filtering techniques to process and analyze the geochemical data. The raster maps of Au, Ag, Cu, As, Pb and Zn were obtained by the multifractal inverse distance weighted (MIDW) method. PCA was used to combine the Au, Ag, Cu, As, Pb, and Zn concentration values. The S-A fractal method was used to decompose the first component pattern achieved by the PCA. The results show that combination anomalies from a combination of variables coincide with the known mineralization of the study area. Although the combination anomalies cannot reflect local anomalies closely enough, high-anomaly areas indicate good sites for further exploration for unknown deposits. On this basis, anomaly and background separation from combination anomalies using fractal filtering techniques can provide guidance for later work.
文摘The distribution of the Mountain ranges, Plateau as well as the distribution of continents and oceans on the earth’s surface are the embodies of the structure and heat states of the materials at the deep crust and of the tectonic stress of regions. There should be a prevalent corresponding between terrestrial height and the texture, thermal and stress states of lithosphere. However, there is no a general consensus on what extent different factors affecting the height of a terrain should be up to now, and this is very apparent for the models of plateau uplifting.1\ Debates on the compensatory depth of crustal equilibrium\;Based on a previous equilibrium model, Woollard(1969) set up an equation to show the relation among the crustal thickness ( D \-m), the depth of Mohorovicic discontinuity(M)and height above sea level( H):D \-m=33.2+8.5 H (km). By this equation it is implied that equilibrium compensation has been reached at the depth of Mohorovicic discontinuity for the height of a terrain. As Woollard (1970)described, there is no evidence to show that mass distribution beneath the Mohorovicic discontinuity ever played an important roles in the equilibrium compensation of the crust.
文摘In NW Himalayas, the suture zone between the collided Indian and the Karakoram plates is occupied by crust of the Cretaceous Kohistan Island\|Arc Terrane [1] . Late Cretaceous (about 90Ma) accretion with the southern margin of the Karakoram Plate at the site of the Shyok Suture Zone turned Kohistan to become an Andean\|type margin. The Neotethys was completely subducted at the southern margin of Kohistan by Early Tertiary, leading to collision between Kohistan and continental crust of the Indian plate at the site of the Main mantle thrust.More than 80% of the Kohistan terrane comprises plutonic rocks of (1) ultramafic to gabbroic composition forming the basal crust of the intra\|oceanic stage of the island arc, and (2) tonalite\|granodiorite\|granite composition belong to the Kohistan Batholith occupying much of the intermediate to shallow crust of the terrane mostly intruded in the Andean\|type margin stage [2] . Both these stages of subduction\|related magmatism were associated with volcanic and sedimentary rocks formed in Late Cretaceous and Early Tertiary basins. This study addresses tectonic configuration of Early Tertiary Drosh basin exposed in NW parts of the Kohistan terrane, immediately to the south of the Shyok Suture Zone.
文摘A detailed survey of 40 Ar/ 39 Ar dating was carried out on basement rocks of the Eastern Kunlun Mountains. The samples were collected from Jinshuikou, Kuhai, Xiaomiao, Wanbaogou and Nachitai groups. All the samples were analysed in 40 Ar/ 39 Ar isotopic dating laboratory of Salzburg University in Austria. The results of 40 Ar/ 39 Ar dating include: (1) The Jinshuikou Group shows hornblende age of 388 5Ma, muscovite at 233～227Ma, and biotite ages between 232 2 and 208 2Ma. These are interpreted to result from amphibolite\|grade Caledonian orogenic diastrophism and low\|grade metamorphic Indosinian overprint. (2) The Xiaomiao Group is characterized by a 40 Ar/ 39 Ar muscovite age of 413 8Ma. (3) The Wanbaogou Group gives out a muscovite age of ca. 160Ma to the S of the Central Kunlun fault. (4) The Nachitai Group revealed a biotite age of ca. 110Ma that was overprinted by a very\|low\|grade event at 60～40 Ma. (5) The Kuhai basement to the S of the Central Kunlun fault is again characterized by a Caledonian age without detectable late overprint: Hornblende: ca. 405Ma, muscovite 376～357Ma, biotite: ca. 360Ma. The new ages constrain that the Kunlun basement essentially formed during Caledonian tectonic events. The basement was locally overprinted by Indosinian tecto\|thermal event in the north of the Central Kunlun fault, and by Jurassic and Paleogene tecto\|thermal events in the south of the Central Kunlun fault.
文摘Qilian orogenic belt is a typical orogenic belt formed by polycyclic collisions between the North China plate and Qaidam microplate. Qilian ocean originated from the rift of the late Proterozoic Rodinia continent(Pangea\|850), evolved through rift basin and became an archipelagic ocean in the Caledonian stage. The Lower Proterozoic strata in Qilian area are mid\|high\|rank metamorphic rocks that constitute the metamorphic basement of the area. The “Huangyuan Movement" (in South Qilian and Central Qilian) and "Alashan Movement" (in North Qilian) in the latest Late Proterozoic formed a regional unconformity. The middle Proterozoic in the area are mudstones and carbonate rocks with stromatolites and ooids. The Qingbaikou System of the upper Proterozoic in the North Qilian and Corridor region is also mudstone and carbonate rock with stromatolites. The Qingbaikou System in Central Qilian is sandstones and mudstones. There are alkaline and tholeiite in the Sinian System in North Qilian and Corridor. The contact between Qingbaikou System and Sinian System is a regional unconformity (Quanji Movement). Qilian ocean began to rift away in Caledonian tectonic stage on the Pre\|Sinian basement.
文摘In accordance with the studies concerning the tectonics of Nei Monggolmade by Huang Jiqing and others, two tectonic units occur in this area:Sino-Korean Platform to the south and Nei Monggol-Greater Khingan Mtsfold system to the north. The dividing line between the two units lies fromBaiyun’ebo on the west to Chifeng on the east. Geophysical studies demonst-rate that there are two gravity gradient zones trending ENE in the northernmargin of the North China Platform. The northern zone is a linear anomalyzone of--50 to--45 mGal extending from Baiyun’ebo in the west to theeast of Chifeng. The southern zone, 60--70km wide, lies from Guyang throughJining to Longhua in the east and its amplitude of gravity gradient amountsto 60 mGal. Field geological survey indicates that there are two main faultedzones. Our recent investigations suggests that there are two Proterozoic riftsof E-W trend in the northern margin of the North China Platform.
文摘The Late Cenozoic fold\|and\|thrust zone along the northwestern margin of the Tarim Basin and the adjacent Tian Shan of Central Asia is an actively deforming part of the India\|Asia collision system. This deformation zone has two remarkable oppositely vergence arcuate fold\|and\|thrust systems (Kepingtage and Kashi\|Atushi fold\|and\|thrust belts) reaching from east of Keping to west of Kashi. This shape is manifested by structure, topography and seismicity. From north to south, this deformation zone is characterized by four main kinematic elements: (1) a hanging\|wall block (Maidan fault and Tuotegongbaizi\|Muziduke thrust system) that represents the Cenozoic reactivation of a late Paleozoic thrust system; (2) an imbricated thrust stack (Kepingtage\|Tashipeshake thrust system) where slices of Tarim platform sediments are thrust south toward the basin; (3) the Kashi\|Atushi fold\|and\|thrust system where thrusting and folding verge toward the Tian Shan; (4) a foot\|wall block (Tarim craton) that dips gently northwest below the sediment\|filled southern Tian Shan basin and generally has little internal deformation.
文摘The tectonic deformation image of Asia Continent can be explained successfully by the model of collision between India secondary continent and Euro\|Asia Plate (P. Molnar and P.Tapponnier, 1975). This paper mainly discusses the characteristics of tectonic deformation and strong earthquake activities on the east border of Tibet Plateau.1\ Characteristics of tectonic deformation on the east border of Tibet Plateau\;Controlled by the flow of the plateau crust material, the movement of the east border of Tibet plateau is mainly horizontal so as to produce two slipping\|block: one results from the slide out of Chuandian Rhombus Block along the SSE direction, the other results from the lateral extrusion of Chuanqing Block with the SEE direction. The slip rate of the north part of Chuandian Rhombus Block, the west region of Sichuan, is 5～8mm/a;2～3mm/a on the south part (the center part of Yunan); the slip rate of Chuanqing is 3～5mm/a and <1mm/a on Longmenshan region (Tang Rongchang, 1993). The slipping features of the blocks directly decide the movement characters of different fault systems: the uniform sinistral shear movement on the east boundary fault of Chuandian Rhombus Block, from the geological viewpoint, the average horizontal slip rate is about 10mm/a, and 5～8mm/a on the Anninghe, Zemuhe and Xiaojiang faults. The dextral shear movement can be found on the west boundary faults composed by Jinshajiang and Honghe faults. Located at the dextral diagonal region between Honghe and Zhongdian faults, the northwestern region of Yunnan shows a tensile stress field with near EW direction and large graben valleys with near NS direction on the ground due to the dextral slip movements of these two faults and slip of Chuandian Rhombus Block along the SSE direction. The normal features of extension tectonic deformation region can be found in this region. Some inner faults (such as Amaniqing, Xiqinglingbeilu) of Chuanqing block show the character of sinistral shear movement with some components of normal slip movement. As the east boundary of Tibet plateau, Minshan and Longmenshan Mountains form the east wall of the plateau. Contrasting to the moving direction of Chuanqing block, the transition from horizontal movement to vertical movement produced the huge nappe reverse deformation in this region, and formed some front\|Mount compensating press\|sag basins such as Gonggaling, Zhangla and Chengdu. Because of the diversity of slip rate of different boundary faults, some clockwise rotating movement can be found in different sub\|blocks.
文摘New results from deep seismic sounding reveal that the Tarim block (basin) was subducted, with gently dipping, to the W.Kunlun Mts. The depths of Moho from north to south are 50km in S.Tarim to 65km in the W. Kunlun Mts. A low velocity and low resistivity layer occurs at the depth of 15～30km, which may be the decollement in the upper crust. A “delamination Crack" might have been formed in the lower crust\|mantle lid, causing the intrusion of alkaline magma along the southern margin of the W. Kunlun Mts. A detailed research for forming and evolving of the Kudi ophiolite in the central part of the W. Kunlun Mts.,which has been given the age of 700～450Ma by using the Re\|Os isotopic dating, and the Radiolarits in chert intercalated with pillow lava are determined to be the late Ordovician to Silurian. Until now we did not find any complete ophiolite suite except Kudi ophiolite. So we suggest that there was no “vast protero\|ocean", and a “limited oceanic basin" exists only during the late Proterozoic to Early Paleozoic, which might have been subducted in Silurian\|Devonian and formed the oldest suture in the north of the Tibet plateau.A suture zone consisting of H. P/T metamorphic blueschist, ophiolitic melange and olistostrome in the north\|western Tibet has been revealed recently, which may extend to NW. connecting with MKT in N. Pakistan.A study of the Fission track thermochronology indicates that the W.Kunlun Mts. has been undergone a pulsatory uplift since 20～18Ma,and a rapid uplift after 3Ma.A model of collision between the Indo\|Pakistan subcontinent\|N.Tibet and the Eurasian blocks of Tarim has been illustrated.
文摘The synorogenic sediments in the foreland basins preserve a potential record of varied depositional environments that respond to and are largely controlled by tectonic events of the mountain along the basin margin. In the exploration of the uplift process of the Qinghai—Tibet Plateau, research on the foreland basins around the plateau is of vital significance. Much work have been carried out on the southern margin along the Himalayas and on the eastern margin, however, seldom work was reported along the northern boundary of the plateau, this have blocked the generation of an integrative image of the evolution of the entire plateau. The Gansu Corridor, located on the northeast margin of the Qinghai—Tibet Plateau, is a Cenozoic foreland basin system formed due to the northward overthrust and overload of the plateau. Thousand of meters detrital sediments derived mainly from denudation of the Qilian orogen have deposited in the basin since Oligocene. Here we report a detailed lithologic and magnetostratigraphic work carried out on the late Cenozoic sedimentary sequences in the Jiuxi Basin, western Gansu Corridor, to investigate the neotectonism of the western Qilian Mt.
文摘Deformation during the uplift of Pamir Since the Himalayan movement, the Punjab block of Indian plate has intruded into the interior of Eurasian plate, produced a protrusive Pamir knot in eastern Tethys. The Pamir knot is where crustal shortening is most intensive in Tethys. After India\|Eurasia collision, giant relief resulted from fast uplifting of Karakorum due to the convergence and underplating in northern and southern margins of Karakorum, the uplifting rates changed with times, and thrusting would be one of the most important factors controlling the uplifting. At the same time, large scale strike\|slip faulting could produced large vertical offsets, so that the exhumation of the rocks from middle and lower crust has drawn much attention. The post\|collisional deformation and evolution of Karakorum would involve the processes of continental escape, crustal shortening and thickening, and orogenic collapse in extensional regime. The thrusting started in late Jurassic and early Cretaceous, but two peaks occurred in late Cretaceous and Eocene, respectively. A large amount of klippen produced by thrusting from north to south have been discovered in the northern slope of the Kungai in front of Pamir. Molnar and Tapponnier noted that the mount of crustal shortening in Pamir would be up to 2000km in the past 40～45Ma, and Coward proposed that 300～400km shortening has happened only in southern Pamir to northern Pakistan. In western Pamir from Kabul of Afghanistan to Quatta of Pakistan, the Chaman left\|lateral strike\|slip fault system extends 1000km long. Multiple structural superposition in eastern Pamir, due to the effects of the uplifting of Qinghai\|Tibet plateau, resulted in complex deformation patterns.
文摘From the planktonic foraminiferal and nannofossil events across the Oligocene/Miocene boundary (OMB) to the major transient glaciation at this epoch boundary,Mi-l,the paleoclimate,stratigraphic and paleontologic events showed a prominent change across the OMB.However,the previous work was mainly about the marine deposits,especially the ocean drilling data.Whatever,the continental strata,such as the alluvial and lacustrine sedimentation in
文摘River evolution at margins of the Tibetan Plateau may provide valuable information for understanding climatic change and tectonic movement of the past. Here we focus on the Huangshui River,a tributary of the Yellow River,crossing a series of tectonically subsided and uplifted areas that show diversity patterns of terrace formation.The distribution of fluvial terrace is studied by mapping and dating.Three terraces in Haiyan basin,four terraces in Huangyuan basin,19 terraces in Xi’ning basin,nine terraces in Ping’an basin,five terraces in Ledu basin and 12 terraces in Minhe basin are recognized.Magne-
文摘The plate tectonic model constructed by R.H. Sillitoe for the origin of porphyry copper deposits said that porphyry copper deposits were associated with convergent plate boundaries and compressional tectonic settings. They were formed along destructive plate margins above subduction zones of oceanic crust. Although this model is suitable for most porphyry copper deposits because the main porphyry copper deposit belts accord with the main Mesozoic or Cenozoic plate subduction zones in space and time in the world, it is difficult to use Sillitoe’s model for explaining the formation of some intracontinental porphyry deposits such as Yulong, the largest one in East Tibet.Having no relation with a subduction zone of plates, Yulong porphyry copper deposit was formed in an intracontinental extensional tectonic setting. Qamdo block, in which Yulong lies, was a small massif in East Tibet. With its Proterozoic crystalline basement and Lower Paleozoic folded basement, Qamdo block had experienced relative stable geologic evolution and a cover more than 20000m in thickness mainly composed of clastic rock and carbonate formed from Devonian to Cretaceous. During this time, although two small oceanic basins(Jinshajiang basin and Lancangjiang basin) between which Qamdo block lay developed and subducted and relevant island arc belts occured along the east and west margins of the block, all of them were closed before Later Triassic. In Cenozoic, mainly from 52 to 35Ma, influenced by the intracontinental convergence of the three large plates(India to the southwest, Tarim to the northwest,and Yangtze to the east), Qamdo block and its surrounding areas (East Tibet) which were just to the west of Yangtze plate were in an intracontinental pull\|apart situation induced by the sinistral strike\|slip fault system while most Himalaya—Kunlun—Tibet areas between India and Tarim plates were in a compression state by the SN\|trending tectonic stress. Controlled by the regional strike\|slip fault systems, the calc\|alkaline magma deriving from the upper mantle or lower crust ascended, occurring porphyry copper mineralization in the relative uplift areas. At the same time, in the relative depression areas, also controlled by the regional deep strike\|slip faults which might cut the lithosphere, several linear or rhombic pull\|apart red molasse basins such as Gongjoe, Nangqen, parallel to the porphyry belt, were formed in this region.
文摘The Tarim basin, located in the northern margin of Tibet, plays a key role in comprehending Tibetan plateau rapid uplift process. Focuses have been on the contribution of basin block to create high mountain (e.g.,Chen and Molnar,1977, Molnar et al.,1993, Ph. Matte, Tapponnier et al.,1996) since 1970. The models, which mainly depend on result of geological survey and other geophysical observation in the region excepted Deep Seismic Sounding, remained unsure because of blank(or absence ) of DSS data until our experiment was performed. How Tarim and west Kunlun to contact in depth ? What different is in crust structure between Tarim and west Kunlun Mt.? This is what we will reply to in our program.We finished the program in 1997. A total of 120 set seismograms (with 3\|component sensors) and 18000kg (AT and TNT) dynamos were used for the DSS field project. 6 shot in Tarim basin and 1 shot in west Kunlun Mt. (Quanshuigou) had been shoot successfully. One shot (Pishan shot) is used as fan\|shape observation (offset is from 150km to 220km) in 6 shots located in Tarim basin. The survey line is along Hotan river across the Tarim basin from the north to the south. In particular, we carried 20 set seismic recorders to Kunlun Mt. to make a short line about 60 km as the southern tendency of our line. The seismic recorders were placed in an interval of 3km from one stations to the next and covered a distance of more than 300km. The stations have to be moved their location per 2\|shotting to form a meeting system or a tracing system (layout). Fig.1 showed our survey line and location of shot as well as recorder stations. Finally we gained 625 cassettes with original seismic record (include cassettes of shooting time recorder et al.). After data process total 1147 quite high\|quality three\|component digital records have been used to analyze. Here, only results of analyzing P wave data is given.
