The Chinese mainland is divided into some tectonic blocks by nearly NE- and EW-orientated faults. Meanwhile strong earthquakes in the Chinese mainland usually cluster in time and space. We call earthquakes in groups. ...The Chinese mainland is divided into some tectonic blocks by nearly NE- and EW-orientated faults. Meanwhile strong earthquakes in the Chinese mainland usually cluster in time and space. We call earthquakes in groups. Tectonic blocks separated by faults and earthquakes in groups are prominent features of the tectonics of the Chi-nese mainland. Correlation between movement of tectonic blocks and groups of earthquakes is discussed in this paper. The results show that earthquakes in groups often occurred at one or several block boundary faults. The released elastic strain energy is built up in the same periods and around blocks. It means that strong earthquakes in groups are mainly caused by movement of blocks. Four types of block movement are identified based ongroup earthquakes: movement along a single boundary of a block (or a combined blocks), movement of a single block, movement of multi-blocks, and movement in block interiors. If we consider distribution of all strong earthquakes occurred in the Chinese mainland, the movement along a single boundary of a block is more popular one inducing strong earthquakes. But if we only consider earthquakes in groups rather than single earthquakesthe movement of a block dominates among four modes. Statistics with respect to group earthquakes show that the Taihangshan mountain and the North China block are much active in the eastern part of Chinese mainland, and in western part of Chinese mainland the active blocks are Sichuan-Yunnan and the Kunlun-Songpan ones.展开更多
When mining metal mines with steep structure planes by the caving method,there is a mechanical model in which the horizontal stress on the rock mass is simplified as a column before surface subsidence.The model is use...When mining metal mines with steep structure planes by the caving method,there is a mechanical model in which the horizontal stress on the rock mass is simplified as a column before surface subsidence.The model is used to deduce critical support load and limiting column length for a given horizontal stress and support pressure.Considering the impact of the column effect,a method is proposed to determine the movement of the ground and caving area in a mine.After surface subsidence,the horizontal stress on a surrounding rock mass can be simplified to a cantilever beam mechanical model.Expressions for its bending fracture length are deduced,and a method is given to determine its stability.On this basis,an explanation for the large ground movement and subsidence scope was given.A case study shows that the damage effect of column and cantilever beam is significant for ground movement in metal-ore mine,and an appropriate correction value should be applied when designing for its angle of ground movements.展开更多
The Menyuan Basin is a structural basin located inside the Qilianshan Mountains, the northern edge of Qinghai—Tibet Plateau, the surface of which is about 3000m ASL. To the south of this basin is the Dabanshan Mounta...The Menyuan Basin is a structural basin located inside the Qilianshan Mountains, the northern edge of Qinghai—Tibet Plateau, the surface of which is about 3000m ASL. To the south of this basin is the Dabanshan Mountain and to the north, the Lenglongling Mountain, which are 4000m ASL.. The neotectonic movement within this area is intense and can be divided into 6 stages.1 The basic data for identifying the stages of the neotectonic movement (1) Deformation of Tertiary deposit: Of the Tertiary system, only Baiyanghe Formation exists in the studied area, distributing at the boundary and under the bottom of the basin with Quaternary deposits discontinuously overlying it. Baiyanghe Formation has been intensely offset and folded, the folding dose not appear in Quaternary deposits. Its exact age remains unknown.(2) Deformation of Quaternary deposits: Most of Quaternary deposits belong to glacial and fluvial deposits, which have been offset and uplifted or sunk by neotectonic movement.(3) Deformation of the geomorphic surfaces: In the studied area exist many types and many orders of geomorphic surfaces, including 2 orders of planation surfaces, 3 orders of glacial platforms, 3 orders of river terraces and 2 orders of alluvial fans. Their ages are dated or comparatively estimated. All of them have been offset and uplifted or subsided by neotectonic movement. They are the time scales for dividing the stages of neotectonic movement.展开更多
Deterministic, probabilistic and composite-grading methods are used to get the possible locations of strong earth-quakes in the future in Norwest Beijing and its vicinity based on the quantitative data and their accur...Deterministic, probabilistic and composite-grading methods are used to get the possible locations of strong earth-quakes in the future in Norwest Beijing and its vicinity based on the quantitative data and their accuracy about active tectonics in the research area and by ordering, some questions in the results are also discussed. It shows that the most dangerous fault segments for strong earthquakes in the future include: segments B and A of the southern boundary fault of the Yangyuan basin, the southern boundary fault of the Xuanhua basin, the east segment of the southern Huaian fault and the east segment of the northern YanggaoTianzhen fault. The most dangerous area is YangyuanShenjing basin, the second one is TianzhenHuaianXuanhua basin and the third dangerous areas are WanquanZhangjiakou and northeast of Yuxian to southwest of Fanshan.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
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
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
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
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
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
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
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
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
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
The geological, geographic and seismicity data indicate that three arc tectonic belt developed on the northeast Pamir, which was the south Pamir arc, the north Pamir arc and the external Pamir arc from south to north....The geological, geographic and seismicity data indicate that three arc tectonic belt developed on the northeast Pamir, which was the south Pamir arc, the north Pamir arc and the external Pamir arc from south to north. In addition to these three belts, there are two nascent arc tectonic belts developed in its fore\|deep depression, the Kashi depression in the northwest Tarim basin, which is the northward propagation of the arc tectonics of northeast Pamir.The south Pamir is an ancient folded belt, composed of the Proterozoic metamorphic layers and igneous complex. It was pushed northward since the collision between the India and Asia, and uplifted since the end of the early Tertiary. The elevation of the Plateau is 4800～5300m, and several intermontane basins distributed in the plateau. At its northeast boundary is the Kalakorum right lateral strike slip fault. Strong strike slip earthquakes occurred along this fault. In the hinterland of the plateau, several normal faulting earthquakes occurred,which are consistent with the extensional dynamic environment of the south Pamir. Deep earthquakes occurred under the 70km depth crust of south Pamir. The N—S cross section of the focal depth show that the earthquake occurred within the south Pamir crust are lower than 70km, and the deep earthquakes with depth of 100～200km occurred in the crystal basement of Tarim basin which are under\|thrusting southward into the root of the south Pamir.展开更多
The Covered Karst, which formed in subsoil environment and distributed in the Tibet Plateau and its eastern district, denuded on the ground surface in different degrees (forming stone pinnacles), but they had the good...The Covered Karst, which formed in subsoil environment and distributed in the Tibet Plateau and its eastern district, denuded on the ground surface in different degrees (forming stone pinnacles), but they had the good consistency in their characteristics. First, some kind of landform, such as stone pinnacles, rock well etc, kept the slippery rock surface. It was believed that they were resulted from the process in soil. Nearer the foot of rock the site was; more clear and integrated the form was. Second, the covered karst often associated with red weathering crust. Based on the character of the red weathering crust of the summit plane of Anduo Mountain, its forming environment was relatively humid and hot. Third, the best geomorphologic position, where the karst was bare, was not on the summit plane but on the slope.The baring degrees and later reworked characteristics of the covered karst made up of an integrated series. They could be divided into three kinds of districts according to their response to the Plateau uplift. (1) The western district, where the uplift was intensive, was mainly Tibet Plateau. For example, in Anduo Mountain, the covered karst was entirely denuded on the ground surface, and the rock surface was turned into mottled rock well because the frost weathering intensively reworked it. The red weathering crust was only kept in the bottom of rock, most of which was observed in the crack of limestone. The present karst process on the ground surface stopped. (2) The middle district, where the uplift degree was moderate, was mainly Yungui Plateau. The covered karst was partly denuded to form the stone pinnacles. Its part, which is baring, is changed to be aciculate and sharp\|pointed, and is active now. (3) The eastern district, where the uplift was weak, was mainly the northern part of Guangxi Province and the southern part of Hunan Province. The covered karst was entirely covered by soil and only observed in the section, which was excavated by human. The form of the covered karst generally had the typical character of the process below the soil.展开更多
There is still no consensus on the mechanisms that have led to the growth and rise of the 3 10 6km\+2 wide and 5000m high Tibet plateau.In one class of models,the whole lithosphere is inferred to deform as a thin visc...There is still no consensus on the mechanisms that have led to the growth and rise of the 3 10 6km\+2 wide and 5000m high Tibet plateau.In one class of models,the whole lithosphere is inferred to deform as a thin viscous sheet.Concurrent thickening of the crust and lithospheric mantle over a vast area absorbs most of the plate convergence.In the thickest region (Tibet),topographic rebound is subsequently triggered by convective removal of the thickened mantle.This is followed by relief collapse and extension.The rebound has a profound effect on climate.Only the final collapse is associated with strike\|slip faulting,which is thus seen as a shallow and minor side\|effect.In another class of models,strain localization along lithospheric shear zones,and decoupling between mantle and crust,are thought to govern the deformation of Asia.Strike\|slip faulting and thrusting combine to cause diachronic uplift of Tibet soon after the onset of collision.The crust thickens but the mantle beneath subducts.At any given time,a small number of boundaries extending to the base of the lithosphere absorb much of the convergence.展开更多
Pakistan has fascinating geology.It exposes Ophiolites in the north and west and sedimentary strata in the south.It preserves lithological and tectonic features of ancient island arc type Himalayan orogeny in the nort...Pakistan has fascinating geology.It exposes Ophiolites in the north and west and sedimentary strata in the south.It preserves lithological and tectonic features of ancient island arc type Himalayan orogeny in the north and Andean type active orogeny in the south.The Main Karakrum Thrust,Kohistan -Ladakh Island arc,Main Mantle Thrust,Main Boundary Thrust and Main Frontal Thrust are展开更多
基金Foundation item: State Key Basic Research Planning Project (G199804070401).
文摘The Chinese mainland is divided into some tectonic blocks by nearly NE- and EW-orientated faults. Meanwhile strong earthquakes in the Chinese mainland usually cluster in time and space. We call earthquakes in groups. Tectonic blocks separated by faults and earthquakes in groups are prominent features of the tectonics of the Chi-nese mainland. Correlation between movement of tectonic blocks and groups of earthquakes is discussed in this paper. The results show that earthquakes in groups often occurred at one or several block boundary faults. The released elastic strain energy is built up in the same periods and around blocks. It means that strong earthquakes in groups are mainly caused by movement of blocks. Four types of block movement are identified based ongroup earthquakes: movement along a single boundary of a block (or a combined blocks), movement of a single block, movement of multi-blocks, and movement in block interiors. If we consider distribution of all strong earthquakes occurred in the Chinese mainland, the movement along a single boundary of a block is more popular one inducing strong earthquakes. But if we only consider earthquakes in groups rather than single earthquakesthe movement of a block dominates among four modes. Statistics with respect to group earthquakes show that the Taihangshan mountain and the North China block are much active in the eastern part of Chinese mainland, and in western part of Chinese mainland the active blocks are Sichuan-Yunnan and the Kunlun-Songpan ones.
基金Project(51274188)supported by the National Natural Science Foundation of China
文摘When mining metal mines with steep structure planes by the caving method,there is a mechanical model in which the horizontal stress on the rock mass is simplified as a column before surface subsidence.The model is used to deduce critical support load and limiting column length for a given horizontal stress and support pressure.Considering the impact of the column effect,a method is proposed to determine the movement of the ground and caving area in a mine.After surface subsidence,the horizontal stress on a surrounding rock mass can be simplified to a cantilever beam mechanical model.Expressions for its bending fracture length are deduced,and a method is given to determine its stability.On this basis,an explanation for the large ground movement and subsidence scope was given.A case study shows that the damage effect of column and cantilever beam is significant for ground movement in metal-ore mine,and an appropriate correction value should be applied when designing for its angle of ground movements.
文摘The Menyuan Basin is a structural basin located inside the Qilianshan Mountains, the northern edge of Qinghai—Tibet Plateau, the surface of which is about 3000m ASL. To the south of this basin is the Dabanshan Mountain and to the north, the Lenglongling Mountain, which are 4000m ASL.. The neotectonic movement within this area is intense and can be divided into 6 stages.1 The basic data for identifying the stages of the neotectonic movement (1) Deformation of Tertiary deposit: Of the Tertiary system, only Baiyanghe Formation exists in the studied area, distributing at the boundary and under the bottom of the basin with Quaternary deposits discontinuously overlying it. Baiyanghe Formation has been intensely offset and folded, the folding dose not appear in Quaternary deposits. Its exact age remains unknown.(2) Deformation of Quaternary deposits: Most of Quaternary deposits belong to glacial and fluvial deposits, which have been offset and uplifted or sunk by neotectonic movement.(3) Deformation of the geomorphic surfaces: In the studied area exist many types and many orders of geomorphic surfaces, including 2 orders of planation surfaces, 3 orders of glacial platforms, 3 orders of river terraces and 2 orders of alluvial fans. Their ages are dated or comparatively estimated. All of them have been offset and uplifted or subsided by neotectonic movement. They are the time scales for dividing the stages of neotectonic movement.
基金National major basic-theory planning project Mechanism and Prediction of Strong Earthquake (95130105) and the Key Project from China Seismological Bureau (95040803).
文摘Deterministic, probabilistic and composite-grading methods are used to get the possible locations of strong earth-quakes in the future in Norwest Beijing and its vicinity based on the quantitative data and their accuracy about active tectonics in the research area and by ordering, some questions in the results are also discussed. It shows that the most dangerous fault segments for strong earthquakes in the future include: segments B and A of the southern boundary fault of the Yangyuan basin, the southern boundary fault of the Xuanhua basin, the east segment of the southern Huaian fault and the east segment of the northern YanggaoTianzhen fault. The most dangerous area is YangyuanShenjing basin, the second one is TianzhenHuaianXuanhua basin and the third dangerous areas are WanquanZhangjiakou and northeast of Yuxian to southwest of Fanshan.
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.
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.
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The geological, geographic and seismicity data indicate that three arc tectonic belt developed on the northeast Pamir, which was the south Pamir arc, the north Pamir arc and the external Pamir arc from south to north. In addition to these three belts, there are two nascent arc tectonic belts developed in its fore\|deep depression, the Kashi depression in the northwest Tarim basin, which is the northward propagation of the arc tectonics of northeast Pamir.The south Pamir is an ancient folded belt, composed of the Proterozoic metamorphic layers and igneous complex. It was pushed northward since the collision between the India and Asia, and uplifted since the end of the early Tertiary. The elevation of the Plateau is 4800～5300m, and several intermontane basins distributed in the plateau. At its northeast boundary is the Kalakorum right lateral strike slip fault. Strong strike slip earthquakes occurred along this fault. In the hinterland of the plateau, several normal faulting earthquakes occurred,which are consistent with the extensional dynamic environment of the south Pamir. Deep earthquakes occurred under the 70km depth crust of south Pamir. The N—S cross section of the focal depth show that the earthquake occurred within the south Pamir crust are lower than 70km, and the deep earthquakes with depth of 100～200km occurred in the crystal basement of Tarim basin which are under\|thrusting southward into the root of the south Pamir.
文摘The Covered Karst, which formed in subsoil environment and distributed in the Tibet Plateau and its eastern district, denuded on the ground surface in different degrees (forming stone pinnacles), but they had the good consistency in their characteristics. First, some kind of landform, such as stone pinnacles, rock well etc, kept the slippery rock surface. It was believed that they were resulted from the process in soil. Nearer the foot of rock the site was; more clear and integrated the form was. Second, the covered karst often associated with red weathering crust. Based on the character of the red weathering crust of the summit plane of Anduo Mountain, its forming environment was relatively humid and hot. Third, the best geomorphologic position, where the karst was bare, was not on the summit plane but on the slope.The baring degrees and later reworked characteristics of the covered karst made up of an integrated series. They could be divided into three kinds of districts according to their response to the Plateau uplift. (1) The western district, where the uplift was intensive, was mainly Tibet Plateau. For example, in Anduo Mountain, the covered karst was entirely denuded on the ground surface, and the rock surface was turned into mottled rock well because the frost weathering intensively reworked it. The red weathering crust was only kept in the bottom of rock, most of which was observed in the crack of limestone. The present karst process on the ground surface stopped. (2) The middle district, where the uplift degree was moderate, was mainly Yungui Plateau. The covered karst was partly denuded to form the stone pinnacles. Its part, which is baring, is changed to be aciculate and sharp\|pointed, and is active now. (3) The eastern district, where the uplift was weak, was mainly the northern part of Guangxi Province and the southern part of Hunan Province. The covered karst was entirely covered by soil and only observed in the section, which was excavated by human. The form of the covered karst generally had the typical character of the process below the soil.
文摘There is still no consensus on the mechanisms that have led to the growth and rise of the 3 10 6km\+2 wide and 5000m high Tibet plateau.In one class of models,the whole lithosphere is inferred to deform as a thin viscous sheet.Concurrent thickening of the crust and lithospheric mantle over a vast area absorbs most of the plate convergence.In the thickest region (Tibet),topographic rebound is subsequently triggered by convective removal of the thickened mantle.This is followed by relief collapse and extension.The rebound has a profound effect on climate.Only the final collapse is associated with strike\|slip faulting,which is thus seen as a shallow and minor side\|effect.In another class of models,strain localization along lithospheric shear zones,and decoupling between mantle and crust,are thought to govern the deformation of Asia.Strike\|slip faulting and thrusting combine to cause diachronic uplift of Tibet soon after the onset of collision.The crust thickens but the mantle beneath subducts.At any given time,a small number of boundaries extending to the base of the lithosphere absorb much of the convergence.
文摘Pakistan has fascinating geology.It exposes Ophiolites in the north and west and sedimentary strata in the south.It preserves lithological and tectonic features of ancient island arc type Himalayan orogeny in the north and Andean type active orogeny in the south.The Main Karakrum Thrust,Kohistan -Ladakh Island arc,Main Mantle Thrust,Main Boundary Thrust and Main Frontal Thrust are
