Uplift\|related geological and geophysical data available from regional geological mapping , detailed structural, tectonic, granitic, volcanic, metamorphic , geochronological studies, deep seismic reflection, wide\|an...Uplift\|related geological and geophysical data available from regional geological mapping , detailed structural, tectonic, granitic, volcanic, metamorphic , geochronological studies, deep seismic reflection, wide\|angle seismic experiment, seismic tomography, broadband seismic network, and magnetotelluric sounding of key areas of the Qinghai—Tibet plateau are radically different from models of plate subduction or collision. Key geological features include: (1) obvio us time difference between plate collision and uplift of the plateau; (2) developments of intracrustal low\|velocity layers , low resistivity layers and discontinuous subhorizontal reflectors; (3) similar results between the rate and time of uplift of the Qinghai\|Tibet plateau and the time and rate of subsidence of its surrounding basins; (4) subhorizontal detachments and metamorphic core complexes occurred in Himalayan and Longmenshan; (5) weak deformation of late Cenozoic sediments and development of major steeply to gently dipping normal faults in the central part of the plateau; (6) discovery of high pressure and ultrahigh pressure metamorphic rocks in Nanbajiawa; (7) young volcanic rocks distributed from the northern plateau to the southern plateau; (8) nearly concordant processes among thrusting , mountain building, horizontal extension and intrusion of leucogranite in Himalayans.展开更多
Based on the drilling,cores,logs,seismic,laboratory analysis and so on,reservoir characteristics and hydrocarbon accumulation of Carboniferous volcanic weathered crust in Zhongguai high area are studied.Volcanic rocks...Based on the drilling,cores,logs,seismic,laboratory analysis and so on,reservoir characteristics and hydrocarbon accumulation of Carboniferous volcanic weathered crust in Zhongguai high area are studied.Volcanic rocks were formed in an island arc environment.The lithology is mainly andesite and tuff;Reservoir spaces are mainly secondary pore,fracture and their combination forms,fractures have a better effect on reservoir seepage;There are four layer structures of volcanic weathered crust,weathered clay layer,strongly weathered zone,weakly weathered zone and unweathered zone and strongly weathered zone is the best,which is the main reservoir development zone;The development of reservoir is mainly affected by weathering-leaching,lithology and lithofacies,and fault(fracture);Effective reservoirs could reach to 480 m thickness(high quality reservoirs are within 240 m).Carboniferous volcanic reservoirs are distributed along three zones,which are near the fault zone,high structural part,favorable lithofacies development zone,and one plane,which is near the unconformity.展开更多
Convective pore-fluid flow (CPFF) plays a critical role in generating mineral deposits and oil reservoirs within the deep Earth. Therefore, theoretical understanding and numerical modeling of the thermodynamic process...Convective pore-fluid flow (CPFF) plays a critical role in generating mineral deposits and oil reservoirs within the deep Earth. Therefore, theoretical understanding and numerical modeling of the thermodynamic process that triggers and controls the CPFF are extremely important for the exploration of new mineral deposits and underground oil resources. From the viewpoint of science, the CPFF within the upper crust can be treated as a kind of thermodynamic instability problem of pore-fluid in fluid-saturated porous media. The key issue of dealing with this kind of problem is to assess whether a nonlinear thermodynamic system under consideration is supercritical. To overcome limitations of using theoretical analysis and experimental methods in dealing with the CPFF problems within the upper crust, finite element modeling has been broadly employed for solving this kind of problem over the past two decades. The main purpose of this paper is to overview recent developments and applications of finite element modeling associated with solving the CPFF problems in large length-scale geological systems of complicated geometries and complex material distributions. In particular, two kinds of commonly-used finite element modeling approaches, namely the steady-state and transient-state approaches, and their advantages/disadvantages are thoroughly presented and discussed.展开更多
A cobalt-enriching crust mining vehicle with four independent driven wheels was proposed. The influence of center-of-gravity position of mining vehicle on obstacle performance was studied. The results show that the mi...A cobalt-enriching crust mining vehicle with four independent driven wheels was proposed. The influence of center-of-gravity position of mining vehicle on obstacle performance was studied. The results show that the mining vehicle has optimal obstacle performance with center-of-gravity position in the middle of suspension. A virtual prototype based on ADAMS software was built and its obstacle performance was simulated. Simulation results show that the mining vehicle with four independent driven wheels has excellent obstacle performance, the maximum climbing capacity is no less than 30°, the maximal ditch width and shoulder height are no less than wheel radius of mining vehicle. Thus wheeled mining vehicle is feasible for cobalt-enriching crust commercial mining.展开更多
Under the condition of the designated collection ratio and the interfused ratio of mullock, to ensure the least energy consumption, the parameters of collecting head （the feed speed, the axes height of collecting hea...Under the condition of the designated collection ratio and the interfused ratio of mullock, to ensure the least energy consumption, the parameters of collecting head （the feed speed, the axes height of collecting head, and the rotate speed） are chosen as the optimized parameters. According to the force on the cutting pick, the collecting size of the cobalt crust and bedrock and the optimized energy consumption of the collecting head, the optimized design model of collecting head is built. Taking two hundred groups seabed microtopography for grand in the range of depth displacement from 4.5 to 5.5 era, then making use of the improved simulated annealing genetic algorithm （SAGA）, the corresponding optimized result can be obtained. At the same time, in order to speed up the controlling of collecting head, the optimization results are analyzed using the regression analysis method, and the conclusion of the second parameter of the seabed microtopography is drawn.展开更多
Recognition of substrates in cobalt crust mining areas can improve mining efficiency.Aiming at the problem of unsatisfactory performance of using single feature to recognize the seabed material of the cobalt crust min...Recognition of substrates in cobalt crust mining areas can improve mining efficiency.Aiming at the problem of unsatisfactory performance of using single feature to recognize the seabed material of the cobalt crust mining area,a method based on multiple-feature sets is proposed.Features of the target echoes are extracted by linear prediction method and wavelet analysis methods,and the linear prediction coefficient and linear prediction cepstrum coefficient are also extracted.Meanwhile,the characteristic matrices of modulus maxima,sub-band energy and multi-resolution singular spectrum entropy are obtained,respectively.The resulting features are subsequently compressed by kernel Fisher discriminant analysis(KFDA),the output features are selected using genetic algorithm(GA)to obtain optimal feature subsets,and recognition results of classifier are chosen as genetic fitness function.The advantages of this method are that it can describe the signal features more comprehensively and select the favorable features and remove the redundant features to the greatest extent.The experimental results show the better performance of the proposed method in comparison with only using KFDA or GA.展开更多
Through integrating the state of the art scientific knowledge in different research fields, some potential mechanisms of large-scale movements of underground pore-fluids such as H2O and CO2 in the continental lithosph...Through integrating the state of the art scientific knowledge in different research fields, some potential mechanisms of large-scale movements of underground pore-fluids such as H2O and CO2 in the continental lithosphere were presented and discussed. The results show that the generation and propagation of porosity waves are important mechanisms to transport mass and heat fluxes from the continental lithospheric mantle into the lower continental crust; the generation and propagation of porosity waves, pore-fluid flow focusing through lower and middle crustal faults, advection of pore-fluids through the lower and middle crust, and whole-crust convection in some particular cases are important mechanisms to transport mass and heat fluxes from the lower into the upper continental crust; heat and mass transport through convective pore-fluid flow is the most effective mechanism of ore body formation and mineralization in hydrothermal systems; due to heat and mass exchange at the interface between the earth surface, hydrosphere and atmosphere, it is very important to consider the hydro-geological effect of the deep earth pore-fluids such as H2O and CO2 on the global warming and climate change in future investigations.展开更多
A Sino\|French joint wide\|angle seismic reflection survey was conducted in eastern Qinghai Province of P. R. China in 1998. There are several geological units in this region, including Sanjiang Fold belt, Bayan Har f...A Sino\|French joint wide\|angle seismic reflection survey was conducted in eastern Qinghai Province of P. R. China in 1998. There are several geological units in this region, including Sanjiang Fold belt, Bayan Har fold belt, eastern Kunkun fold belt, western Qingling fold belt, Qaidam basin and Qilian fold belt. The seismic data acquired in the seismic experiment provides an abundant information and reveals the detailed crustal velocity structure and differences between all the tectonic units in this region. These results will help us to understand the evolution procedure and mechanism of the formation of Qinghai—Xizang plateau.According to the seismic data, several reflection phases were identified. After the phase correlation, the reflectivity method and Dynamic Ray Tracing were applied simultaneously to model the 1\|D velocity structure for different tectonic units, actually to determine the velocity distribution within the crust. Based on the 1\|D depth\|velocity function, keeping the layer\|velocities fixed and only adjusting the shape of the reflectors to fit the observed data by Dynamic Ray Tracing, the 2\|D crustal velocity structures were established for each tectonic unit. The results show that there are some obvious differences between Sanjiang and Bayan Har. The crust is about 76km thick with an average velocity of 6 33km/s in Sanjiang region, but about 64km with an average velocity of 6 26km/s in Bayan Har. On the other hand, the velocity of lower crust in Sanjian is lower (about 6 65km/s) than in Bayan Har (about 6 90km/s), and the thickness of the lower crust in Sanjiang is much thicker than in Bayan Har. A low velocity layer ( v p=5 80～5 85km/s) exists on both sides of Jinsha fault. These evidences indicate the existence of Jinsha suture.展开更多
The fieldwork and experiments indicate that the red weathering crust, which developed on the limestone of Tibet Plateau and its eastern district, is a component of common planation surface of karst. The evidences are ...The fieldwork and experiments indicate that the red weathering crust, which developed on the limestone of Tibet Plateau and its eastern district, is a component of common planation surface of karst. The evidences are as follows: (1) They distributed in transverse continuity and often covered on the summit plane of hills. They correspond with a certain geomorphologic surface, for example, near Lijiang of Yunnan, there are summit planes of little undulation, the red weathering crust of large area distributed on the summit plane, and there are also many dolines and closed depressions up to hundreds of meters in diameter. (2) According to the situation of karst development, the soil loss made the fine sediments to be washed away through the crack in the district which vertical process developed well. Therefore, even if in the most active district of karst process, the weathering crust of continuous heavy layer can not be formed only if there existed a certain undulation. The organic soil and redizina can only be formed, and their main types of soil profile are AF\|D and A\|D. The thick weathering crust is only observed on the karst plane nearby base\|level of erosion. (3) The existence of terra rossa indicates the humid tropical/subtropical environment. The study results show that the component of red weathering crust on the limestone generally had the character of high content of clay particles(<2μm) and the weak process of silicon losing and aluminium concentration comparing with typical terra rossa. These characters indicate that its forming environment was humid and eluviation was weak. This situation only existed in the peneplain environment where groundwater was shallow and drainage condition was not very well. In a word, the forming time of thick weathering crust in the limestone district corresponded with the period of peneplain, and the forming altitude height was near the base level of erosion. So the red weathering crust of limestone had the significance of geomorphologic stage. These knowledges were important for assessing of the degree of Tibet Plateau uplift by the use of red weathering crust.展开更多
We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersi...We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersion data. Thickness and S\|wave velocity of each sub layer are taken from Love wave dispersion data, then P\|wave velocity structure was deduced using Rayleigh wave dispersion data. Densities of sub layers were estimated by the empirical relationships between seismic velocity and rock density. Having S\| and P\|wave velocities, v p/ v s ratio is calculated for each sub layer. Six sub layers in crust of Tibetan Plateau has been identified, which are 0～8km, 8～30km, 30～40km, 40～62km, 62～68km and 68～75km respectively. The S\|wave velocity structure of the Plateau is 3 13, 3 32, 3 15, 3 92, 3 45 and 3 87 km/s for each sub layer; and P\|wave velocities are 6 00, 6 10, 5 72, 6 35, 6 78 and 6 64km/s respectively v p/ v s ratios in sub layers are 1 92, 1 84, 1 82, 1 62, 1 96 and 1 72; and corresponding Poisson ratios are 0 31, 0 29, 0 28, 0 19, 0 32 and 0 24. Our result on Poisson ratios of Tibetan crust was supported by seismic waveform modelling by Rodgers and Schwartz (1998).展开更多
The isotopic signature of mid\|ocean ridge basalts (MORB) from the Indian Ocean is different from that of MORB from the Pacific and North\|Atlantic oceans.. The Indian MORB is characterized by lower 206 Pb/ 204 Pb, hi...The isotopic signature of mid\|ocean ridge basalts (MORB) from the Indian Ocean is different from that of MORB from the Pacific and North\|Atlantic oceans.. The Indian MORB is characterized by lower 206 Pb/ 204 Pb, hi gher 87 Sr/ 86 Sr, and lower 206 Pb/ 204 Pb for given 143 Nd/ 144 Nd than the latter (Hart, 1984; Castillo, 1988; Mahoney et al., 1998). Why the Indian Ocean mantle domain is different from the Pacific and North\|Atlantic ocean mantle domain is still unclear. Two general classes of hypotheses have been proposed to explain the origin of Indian mantle (Mahoney et al., 1998). The first one is that the components of the Indian Ocean mantle domain are a fairly young mantle end\|member created during the processes of breakup of the Gondwana continent to form the Indian Ocean. The second hypothesis posits that the Indian MORB\|type isotopic signature is a long\|lived mantle domain that existed prior to the formation of the present Indian Ocean. Thus it appears that one of the keys to a better understanding of origin of the Indian Ocean\|type isotopic signature depends on its age. Although some studies (Mahoney et al., 1998; Weis and Frey, 1997) showed that the isotopic signature was as old as the Indian ocean crust (140Ma), basalts investigated in the Indian Ocean region do not prove or disprove the existence of the Indian MORB\|type isotopic signature prior to the Indian Ocean because they were taken from the Indian ocean basin itself.展开更多
Reversions as receiver functions and ACH were performed using the teleseismic data acquired from the seismic array that were deployed across Tian Shan in Xinjiang in 1997\|1998 jointly by Sino\|French seismic crew.The...Reversions as receiver functions and ACH were performed using the teleseismic data acquired from the seismic array that were deployed across Tian Shan in Xinjiang in 1997\|1998 jointly by Sino\|French seismic crew.The results suggest the crustal shortening and thickening in the study area that are well expressed by the thickening in lower crust and the uplifting of Tian Shan in the collision between Euro\|Asian and Indian plates. Underthrusting in the intra\|continental collision model turns out to be asymmetrical, with the northward in the south much stronger than the southward in the north. The cause of the steepness of the southward underthrust is likely to rest on the strong extrusion. Going further deep, the curving end of the cold underthrusting zone may detach, penetrating its own way. The ongoing uplifting of Tian Shan is given birth mostly by the underthrusting on its south and the squeezing force from both sides. The underthrusting zone is composed of compact ancestral crystalline rocks. The thickness of the crust varys from 65km beneath the main body of Tian Shan to 41km beneath the Tarim and Zengar basins on sides with certain degree of thickening. The major faulting zones in the area go precipitously in the scope of crust, with those in the low\|velocity bodies closely associated to the activities of molten mantle materials and seismicity.展开更多
Comparatively analyzing 47 REE distribution data of the Southern Hunan geosynclinal arkosesilicarenite and various period granitic rocks and the results of their partially melting experiment series in company with the...Comparatively analyzing 47 REE distribution data of the Southern Hunan geosynclinal arkosesilicarenite and various period granitic rocks and the results of their partially melting experiment series in company with the occurence and petrogeochemical features of various period granitic rocks, the authors suggest that all of the abovementioned salic rocks can be partially melt to produce granitic magma.展开更多
Compared with the oceanic crust, knowledge about the formation of the continental crust (CC) is relatively poor. Although melting of subducted slabs in the early history of the Earth has been considered as the maj... Compared with the oceanic crust, knowledge about the formation of the continental crust (CC) is relatively poor. Although melting of subducted slabs in the early history of the Earth has been considered as the major way that shaped the chemical characteristics of the CC by most geologists, as the CC shares many characteristics with modern adakites, some geologists argued that Archean TTG was formed in the same way as modern arcs rather than slab melting, whereas others proposed that melting at the bottom of the thickened oceanic crust was more important. Recently,the debate is mainly focused on the unique subchondritic Nb/Ta value of the CC, and particularly, how Nb and Ta fractionated from each other and consequently how, in detail, the CC was built.……展开更多
文摘Uplift\|related geological and geophysical data available from regional geological mapping , detailed structural, tectonic, granitic, volcanic, metamorphic , geochronological studies, deep seismic reflection, wide\|angle seismic experiment, seismic tomography, broadband seismic network, and magnetotelluric sounding of key areas of the Qinghai—Tibet plateau are radically different from models of plate subduction or collision. Key geological features include: (1) obvio us time difference between plate collision and uplift of the plateau; (2) developments of intracrustal low\|velocity layers , low resistivity layers and discontinuous subhorizontal reflectors; (3) similar results between the rate and time of uplift of the Qinghai\|Tibet plateau and the time and rate of subsidence of its surrounding basins; (4) subhorizontal detachments and metamorphic core complexes occurred in Himalayan and Longmenshan; (5) weak deformation of late Cenozoic sediments and development of major steeply to gently dipping normal faults in the central part of the plateau; (6) discovery of high pressure and ultrahigh pressure metamorphic rocks in Nanbajiawa; (7) young volcanic rocks distributed from the northern plateau to the southern plateau; (8) nearly concordant processes among thrusting , mountain building, horizontal extension and intrusion of leucogranite in Himalayans.
基金Project (51674211) supported by the National Natural Science Foundation of ChinaProject (51534006) supported by the Key Projects of the Natural Science Foundation,ChinaProject (2017ZX05036003-003) supported by the National Science and Technology Project of China
文摘Based on the drilling,cores,logs,seismic,laboratory analysis and so on,reservoir characteristics and hydrocarbon accumulation of Carboniferous volcanic weathered crust in Zhongguai high area are studied.Volcanic rocks were formed in an island arc environment.The lithology is mainly andesite and tuff;Reservoir spaces are mainly secondary pore,fracture and their combination forms,fractures have a better effect on reservoir seepage;There are four layer structures of volcanic weathered crust,weathered clay layer,strongly weathered zone,weakly weathered zone and unweathered zone and strongly weathered zone is the best,which is the main reservoir development zone;The development of reservoir is mainly affected by weathering-leaching,lithology and lithofacies,and fault(fracture);Effective reservoirs could reach to 480 m thickness(high quality reservoirs are within 240 m).Carboniferous volcanic reservoirs are distributed along three zones,which are near the fault zone,high structural part,favorable lithofacies development zone,and one plane,which is near the unconformity.
基金Project(11272359)supported by the National Natural Science Foundation of China
文摘Convective pore-fluid flow (CPFF) plays a critical role in generating mineral deposits and oil reservoirs within the deep Earth. Therefore, theoretical understanding and numerical modeling of the thermodynamic process that triggers and controls the CPFF are extremely important for the exploration of new mineral deposits and underground oil resources. From the viewpoint of science, the CPFF within the upper crust can be treated as a kind of thermodynamic instability problem of pore-fluid in fluid-saturated porous media. The key issue of dealing with this kind of problem is to assess whether a nonlinear thermodynamic system under consideration is supercritical. To overcome limitations of using theoretical analysis and experimental methods in dealing with the CPFF problems within the upper crust, finite element modeling has been broadly employed for solving this kind of problem over the past two decades. The main purpose of this paper is to overview recent developments and applications of finite element modeling associated with solving the CPFF problems in large length-scale geological systems of complicated geometries and complex material distributions. In particular, two kinds of commonly-used finite element modeling approaches, namely the steady-state and transient-state approaches, and their advantages/disadvantages are thoroughly presented and discussed.
基金Project(DY105-03-02) supported by the State Council Ocean Special Foundation of China
文摘A cobalt-enriching crust mining vehicle with four independent driven wheels was proposed. The influence of center-of-gravity position of mining vehicle on obstacle performance was studied. The results show that the mining vehicle has optimal obstacle performance with center-of-gravity position in the middle of suspension. A virtual prototype based on ADAMS software was built and its obstacle performance was simulated. Simulation results show that the mining vehicle with four independent driven wheels has excellent obstacle performance, the maximum climbing capacity is no less than 30°, the maximal ditch width and shoulder height are no less than wheel radius of mining vehicle. Thus wheeled mining vehicle is feasible for cobalt-enriching crust commercial mining.
基金Project(50875265) supported by the National Natural Science Foundation of ChinaProject(20080440992) supported by the Postdoctoral Science Foundation of ChinaProject(2009SK3159) supported by the Technology Support Plan of Hunan Province,China
文摘Under the condition of the designated collection ratio and the interfused ratio of mullock, to ensure the least energy consumption, the parameters of collecting head （the feed speed, the axes height of collecting head, and the rotate speed） are chosen as the optimized parameters. According to the force on the cutting pick, the collecting size of the cobalt crust and bedrock and the optimized energy consumption of the collecting head, the optimized design model of collecting head is built. Taking two hundred groups seabed microtopography for grand in the range of depth displacement from 4.5 to 5.5 era, then making use of the improved simulated annealing genetic algorithm （SAGA）, the corresponding optimized result can be obtained. At the same time, in order to speed up the controlling of collecting head, the optimization results are analyzed using the regression analysis method, and the conclusion of the second parameter of the seabed microtopography is drawn.
基金Project(51874353)supported by the National Natural Science Foundation of ChinaProject(GCX20190898Y)supported by Mittal Student Innovation Project,China。
文摘Recognition of substrates in cobalt crust mining areas can improve mining efficiency.Aiming at the problem of unsatisfactory performance of using single feature to recognize the seabed material of the cobalt crust mining area,a method based on multiple-feature sets is proposed.Features of the target echoes are extracted by linear prediction method and wavelet analysis methods,and the linear prediction coefficient and linear prediction cepstrum coefficient are also extracted.Meanwhile,the characteristic matrices of modulus maxima,sub-band energy and multi-resolution singular spectrum entropy are obtained,respectively.The resulting features are subsequently compressed by kernel Fisher discriminant analysis(KFDA),the output features are selected using genetic algorithm(GA)to obtain optimal feature subsets,and recognition results of classifier are chosen as genetic fitness function.The advantages of this method are that it can describe the signal features more comprehensively and select the favorable features and remove the redundant features to the greatest extent.The experimental results show the better performance of the proposed method in comparison with only using KFDA or GA.
基金Project(10672190) supported by the National Natural Science Foundation of China
文摘Through integrating the state of the art scientific knowledge in different research fields, some potential mechanisms of large-scale movements of underground pore-fluids such as H2O and CO2 in the continental lithosphere were presented and discussed. The results show that the generation and propagation of porosity waves are important mechanisms to transport mass and heat fluxes from the continental lithospheric mantle into the lower continental crust; the generation and propagation of porosity waves, pore-fluid flow focusing through lower and middle crustal faults, advection of pore-fluids through the lower and middle crust, and whole-crust convection in some particular cases are important mechanisms to transport mass and heat fluxes from the lower into the upper continental crust; heat and mass transport through convective pore-fluid flow is the most effective mechanism of ore body formation and mineralization in hydrothermal systems; due to heat and mass exchange at the interface between the earth surface, hydrosphere and atmosphere, it is very important to consider the hydro-geological effect of the deep earth pore-fluids such as H2O and CO2 on the global warming and climate change in future investigations.
文摘A Sino\|French joint wide\|angle seismic reflection survey was conducted in eastern Qinghai Province of P. R. China in 1998. There are several geological units in this region, including Sanjiang Fold belt, Bayan Har fold belt, eastern Kunkun fold belt, western Qingling fold belt, Qaidam basin and Qilian fold belt. The seismic data acquired in the seismic experiment provides an abundant information and reveals the detailed crustal velocity structure and differences between all the tectonic units in this region. These results will help us to understand the evolution procedure and mechanism of the formation of Qinghai—Xizang plateau.According to the seismic data, several reflection phases were identified. After the phase correlation, the reflectivity method and Dynamic Ray Tracing were applied simultaneously to model the 1\|D velocity structure for different tectonic units, actually to determine the velocity distribution within the crust. Based on the 1\|D depth\|velocity function, keeping the layer\|velocities fixed and only adjusting the shape of the reflectors to fit the observed data by Dynamic Ray Tracing, the 2\|D crustal velocity structures were established for each tectonic unit. The results show that there are some obvious differences between Sanjiang and Bayan Har. The crust is about 76km thick with an average velocity of 6 33km/s in Sanjiang region, but about 64km with an average velocity of 6 26km/s in Bayan Har. On the other hand, the velocity of lower crust in Sanjian is lower (about 6 65km/s) than in Bayan Har (about 6 90km/s), and the thickness of the lower crust in Sanjiang is much thicker than in Bayan Har. A low velocity layer ( v p=5 80～5 85km/s) exists on both sides of Jinsha fault. These evidences indicate the existence of Jinsha suture.
文摘The fieldwork and experiments indicate that the red weathering crust, which developed on the limestone of Tibet Plateau and its eastern district, is a component of common planation surface of karst. The evidences are as follows: (1) They distributed in transverse continuity and often covered on the summit plane of hills. They correspond with a certain geomorphologic surface, for example, near Lijiang of Yunnan, there are summit planes of little undulation, the red weathering crust of large area distributed on the summit plane, and there are also many dolines and closed depressions up to hundreds of meters in diameter. (2) According to the situation of karst development, the soil loss made the fine sediments to be washed away through the crack in the district which vertical process developed well. Therefore, even if in the most active district of karst process, the weathering crust of continuous heavy layer can not be formed only if there existed a certain undulation. The organic soil and redizina can only be formed, and their main types of soil profile are AF\|D and A\|D. The thick weathering crust is only observed on the karst plane nearby base\|level of erosion. (3) The existence of terra rossa indicates the humid tropical/subtropical environment. The study results show that the component of red weathering crust on the limestone generally had the character of high content of clay particles(<2μm) and the weak process of silicon losing and aluminium concentration comparing with typical terra rossa. These characters indicate that its forming environment was humid and eluviation was weak. This situation only existed in the peneplain environment where groundwater was shallow and drainage condition was not very well. In a word, the forming time of thick weathering crust in the limestone district corresponded with the period of peneplain, and the forming altitude height was near the base level of erosion. So the red weathering crust of limestone had the significance of geomorphologic stage. These knowledges were important for assessing of the degree of Tibet Plateau uplift by the use of red weathering crust.
文摘We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersion data. Thickness and S\|wave velocity of each sub layer are taken from Love wave dispersion data, then P\|wave velocity structure was deduced using Rayleigh wave dispersion data. Densities of sub layers were estimated by the empirical relationships between seismic velocity and rock density. Having S\| and P\|wave velocities, v p/ v s ratio is calculated for each sub layer. Six sub layers in crust of Tibetan Plateau has been identified, which are 0～8km, 8～30km, 30～40km, 40～62km, 62～68km and 68～75km respectively. The S\|wave velocity structure of the Plateau is 3 13, 3 32, 3 15, 3 92, 3 45 and 3 87 km/s for each sub layer; and P\|wave velocities are 6 00, 6 10, 5 72, 6 35, 6 78 and 6 64km/s respectively v p/ v s ratios in sub layers are 1 92, 1 84, 1 82, 1 62, 1 96 and 1 72; and corresponding Poisson ratios are 0 31, 0 29, 0 28, 0 19, 0 32 and 0 24. Our result on Poisson ratios of Tibetan crust was supported by seismic waveform modelling by Rodgers and Schwartz (1998).
文摘The isotopic signature of mid\|ocean ridge basalts (MORB) from the Indian Ocean is different from that of MORB from the Pacific and North\|Atlantic oceans.. The Indian MORB is characterized by lower 206 Pb/ 204 Pb, hi gher 87 Sr/ 86 Sr, and lower 206 Pb/ 204 Pb for given 143 Nd/ 144 Nd than the latter (Hart, 1984; Castillo, 1988; Mahoney et al., 1998). Why the Indian Ocean mantle domain is different from the Pacific and North\|Atlantic ocean mantle domain is still unclear. Two general classes of hypotheses have been proposed to explain the origin of Indian mantle (Mahoney et al., 1998). The first one is that the components of the Indian Ocean mantle domain are a fairly young mantle end\|member created during the processes of breakup of the Gondwana continent to form the Indian Ocean. The second hypothesis posits that the Indian MORB\|type isotopic signature is a long\|lived mantle domain that existed prior to the formation of the present Indian Ocean. Thus it appears that one of the keys to a better understanding of origin of the Indian Ocean\|type isotopic signature depends on its age. Although some studies (Mahoney et al., 1998; Weis and Frey, 1997) showed that the isotopic signature was as old as the Indian ocean crust (140Ma), basalts investigated in the Indian Ocean region do not prove or disprove the existence of the Indian MORB\|type isotopic signature prior to the Indian Ocean because they were taken from the Indian ocean basin itself.
文摘Reversions as receiver functions and ACH were performed using the teleseismic data acquired from the seismic array that were deployed across Tian Shan in Xinjiang in 1997\|1998 jointly by Sino\|French seismic crew.The results suggest the crustal shortening and thickening in the study area that are well expressed by the thickening in lower crust and the uplifting of Tian Shan in the collision between Euro\|Asian and Indian plates. Underthrusting in the intra\|continental collision model turns out to be asymmetrical, with the northward in the south much stronger than the southward in the north. The cause of the steepness of the southward underthrust is likely to rest on the strong extrusion. Going further deep, the curving end of the cold underthrusting zone may detach, penetrating its own way. The ongoing uplifting of Tian Shan is given birth mostly by the underthrusting on its south and the squeezing force from both sides. The underthrusting zone is composed of compact ancestral crystalline rocks. The thickness of the crust varys from 65km beneath the main body of Tian Shan to 41km beneath the Tarim and Zengar basins on sides with certain degree of thickening. The major faulting zones in the area go precipitously in the scope of crust, with those in the low\|velocity bodies closely associated to the activities of molten mantle materials and seismicity.
文摘Comparatively analyzing 47 REE distribution data of the Southern Hunan geosynclinal arkosesilicarenite and various period granitic rocks and the results of their partially melting experiment series in company with the occurence and petrogeochemical features of various period granitic rocks, the authors suggest that all of the abovementioned salic rocks can be partially melt to produce granitic magma.
文摘 Compared with the oceanic crust, knowledge about the formation of the continental crust (CC) is relatively poor. Although melting of subducted slabs in the early history of the Earth has been considered as the major way that shaped the chemical characteristics of the CC by most geologists, as the CC shares many characteristics with modern adakites, some geologists argued that Archean TTG was formed in the same way as modern arcs rather than slab melting, whereas others proposed that melting at the bottom of the thickened oceanic crust was more important. Recently,the debate is mainly focused on the unique subchondritic Nb/Ta value of the CC, and particularly, how Nb and Ta fractionated from each other and consequently how, in detail, the CC was built.……
