Yushenfu mining area is located in an ecological fragile area in western China, the coal seam of which is the Jurassic Ysn'an Foirnalion. The Jurassic Yan'an Formation con tains five minable coal seams, the to...Yushenfu mining area is located in an ecological fragile area in western China, the coal seam of which is the Jurassic Ysn'an Foirnalion. The Jurassic Yan'an Formation con tains five minable coal seams, the top layer of which is thick, covered by shallow overburden and located under aquifers. Therefore, the mining induced water flowing fractured zone can easily extend to the aquifers of both the Quaternary Sarahu and Jurassic Zhiluo Formation. This would result in a series of negative hydrological and ecological effects, including groundwater leakage, groundwater lowering, furtherly causing surface vegetation withering and dying, surface water body reduction, spring drying out, and water flow of river being decreased substantially. To solve these environmental problems, several technologies have been carried out by Chinese scientists, one of which is water-preserved coal mining. This paper presents a review of the origin, definition and development of water-preserved coal mining, and its applications in Yushenfu mining area. The applicable conditions, research contents, research methodology, and technical foundation of water-preserved coal mining are addressed in this paper. The future research focuses regarding water-preserved coal mining in China are also discussed in this paper. Its results serve as a guide for selecting the methods to be preferred for mining in case the geological conditions, roof overburden structure and coal mining process are similar to Yushenfu mining area.展开更多
The western Sichuan hydrothermal area is located at the northeastern margin of the eastern syntaxis of the Qinghai-Tibet Plateau, which is also the eastern end of the Mediterranean-Himalayan geothermal activity zone. ...The western Sichuan hydrothermal area is located at the northeastern margin of the eastern syntaxis of the Qinghai-Tibet Plateau, which is also the eastern end of the Mediterranean-Himalayan geothermal activity zone. There are 248 warm or hot springs in this area, and 11 have temperatures beyond the local boiling temperature. Most of these hot springs are distributed along the Jinshajiang, Dege-Xiangcheng, Ganzi-Litang, and Xianshuihe faults, forming a NW-SE hydrothermal belt. A geothermal analysis of this high-temperature hydrothermal area is an important basis for understanding the deep geodynamic process of the eastern syntaxis of the Qinghai-Tibet Plateau. In addition, this study offers an a priori view to utilize geothermal resources, which is important in both scientific research and application. We use gravity, magnetic, seismic, and helium isotope data to analyze the crust-mantle heat flow ratio and deep geothermal structure. The results show that the background terrestrial heat flow descends from southwest to northeast. The crustal heat ratio is not more than 60%. The high temperature hydrothermal active is related to crustal dynamics processes. Along the Batang-Litang-Kangding line, the Moho depth increases eastward, which is consistent with the changing Qc/Qm(crustal/mantle heat flow) ratio trend. The geoid in the hydrothermal zone is 4–6 km higher than the surroundings, forming a local "platform". The NW-SE striking local tensile stress zone and uplift structure in the upper and middle crust corresponds with the surface hydrothermal active zone. There is an average Curie Point Depth(CPD) of 19.5–22.5 km in Batang, Litang, and Kangding. The local shear-wave(S-wave) velocity is relatively low in the middle and lower crust. The S-wave shows a low velocity trap(Vs<3.2 km s.1) at 15–30 km, which is considered a high-temperature partial melting magma, the crustal source of the hydrothermal active zone. We conclude that the hydrothermal system in this area can be divided into Batang-type and Kangding-t展开更多
Objective Eclogites are important indicators of ancient plate boundaries or paleosuture zones. Despite their great geological significance, very few investigations have been carried out in the Kunlun region. The Centr...Objective Eclogites are important indicators of ancient plate boundaries or paleosuture zones. Despite their great geological significance, very few investigations have been carried out in the Kunlun region. The Central East Kunlun fault zone was believed to be an Early Paleozoic suture zone, but there has been no reliable evidence for this, though studies on ophiolite, granite, and basic granulite indicate that the Early Paleozoic orogeny occurred in the East Kunlun. This work focused on the Dagele eclogites in Central East Kunlun to provide new constraints for the Central East Kunlun suture zone.展开更多
Recent seismic evidence shows that basalt accumulation is widespread in the mantle transition zone(MTZ),yet its ubiquity or sporadic nature remains uncertain.To investigate this phenomenon further,we characterized the...Recent seismic evidence shows that basalt accumulation is widespread in the mantle transition zone(MTZ),yet its ubiquity or sporadic nature remains uncertain.To investigate this phenomenon further,we characterized the velocity structure across the 660-km discontinuity that separates the upper mantle from the lower mantle beneath the Sea of Okhotsk by modeling the waveform of the S660P phase,a downgoing S wave converting into a P wave at the 660-km interface.These waves were excited by two regional>410-km-deep events and were recorded by stations in central Asia.Our findings showed no need to introduce velocity anomalies at the base of the MTZ to explain the S660P waveforms because the IASP91 model adequately reproduced the waveforms.This finding indicates that the basalt accumulation has not affected the bottom of the MTZ in the study area.Instead,this discontinuity is primarily controlled by temperature or water content variations,or both.Thus,we argue that the basalt accumulation at the base of the MTZ is sporadic,not ubiquitous,reflecting its heterogeneous distribution.展开更多
Detailed work on Quaternary volcanism has been carried out in the Mermoz and Fann sectors of western Senegal. In the Mermoz sector, the main emission zone is a collapsed crater located at the intersection of three maj...Detailed work on Quaternary volcanism has been carried out in the Mermoz and Fann sectors of western Senegal. In the Mermoz sector, the main emission zone is a collapsed crater located at the intersection of three major fractures: NE-SW, NW-SE and N-S. The lithological succession in this Mermoz sector comprises, from bottom to top: 1) a substratum with at its base Eocene limestones on which lie Quaternary sands surmounted by stratified tuffs;2) a vesicular ball dolerite which deforms the stratified tuffs;3) a dark early breccia;4) two generations of basanites: the first is vesicular, the second non-vesicular;5) a clear intermediate breccia and finally 6) a late breccia. The Fann sector contains several emission zones, most of which are currently located in the ocean. The lavas may have reached the coast through E-W and NE-SW faults. The lithological succession includes from bottom to top: 1) scoria-rich early volcanic breccias;2) a first generation of non-vesicular mesocrate dolerite (D1);3) a second generation of melanocrate vesicular dolerite (D2);4) basanites and finally 5) a late breccia. The geochemical characteristics of the lavas studied are compatible with a very enriched and very deep magmatic source of the garnet lherzolite type located in the lower mantle. The magma from this source would have risen in the form of mantle plumes through major NE-SW and E-W faults in a continental intraplate context.展开更多
The objectives of Integrated Ecosystem Assessment for Western Development of China includes: (1) providing scientific basis for ecosystem protection, ecosystem management and ecological construction in the western dev...The objectives of Integrated Ecosystem Assessment for Western Development of China includes: (1) providing scientific basis for ecosystem protection, ecosystem management and ecological construction in the western development; (2) developing complete database and analytical tools and strengthening decision-making support capacity; and (3) improving ecosystem management in China, spreading ecological knowledge to the public, serving decision-making of local and central governments, and promoting socio-economic sustainable development. The design and implementation of the project are of significance under the macro background of western development of China. By the integrated assessment of western China, we can get the first-hand data covering all the environmental factors as well as disclose the situations and their changing trends of ecosystem in the western part of China, which will benefit the decision-making for the central and local governments in the implementation of the western development strategy. In other words, the implementation of the project, to a certain extent, can guarantee the regional sustainable development of western China.展开更多
The Neogene is an important period for studying the onset of subduction,with numerous subduction zones forming in the western Pacific,including the Ryukyu,Manila,Philippine,North Sulawesi,Halmahera,New Britain,Solomon...The Neogene is an important period for studying the onset of subduction,with numerous subduction zones forming in the western Pacific,including the Ryukyu,Manila,Philippine,North Sulawesi,Halmahera,New Britain,Solomon,and New Hebrides subduction zones.However,studies on these subduction zones are relatively independent,so it is important to conduct systematic comparative studies.In this paper,we review the initiation models of Neogene subduction in the western Pacific,with the three typical types of subduction initiation models including polarity-reversal,induced subduction re-initiation,and noninherited subduction initiation to form new ruptures.In addition,the parameters of different subduction zones are collated to form five categories:basic features,subducting plate features,upper plate features,kinematic features,and subsequent activity.The regularity of the subduction processes,the specificity of the different subduction cases,and the possible constraints between the subduction initiation types and the characteristics of the subduction zone parameters are discussed and analyzed.The compiled dataset of the subduction zone parameters can provide data support for related studies.展开更多
Knowing the phase relations of carbon-bearing phases at high-pressure(HP) and high-temperature(HT) condition is essential for understanding the deep carbon cycle in the subduction zones.In particular,the phase relatio...Knowing the phase relations of carbon-bearing phases at high-pressure(HP) and high-temperature(HT) condition is essential for understanding the deep carbon cycle in the subduction zones.In particular,the phase relation of carbon-bearing phases is also strongly influenced by redox condition of subduction zones,which is poorly explored.Here we summarized the phase relations of carbon-bearing phases(calcite,aragonite,dolomite,magnesite,graphite,hydrocarbon) in HP metamorphic rocks(marble,metapelite,eclogite) from the Western Tianshan subduction zone and high-pressure experiments.During prograde progress of subduction,carbonates in altered oceanic crust change from Ca-carbonate(calcite) to Ca,Mg-carbonate(dolomite),then finally to Mgcarbonate(magnesite) via Mg-Ca cation exchange reaction between silicate and carbonate,while calcite in sedimentary calcareous ooze on oceanic crust directly transfers to high-pressure aragonite in marble or amorphous CaCO3 in subduction zones.Redox evolution also plays a significant effect on the carbon speciation in the Western Tianshan subduction zone.The prograde oxygen fugacity of the Western Tianshan subduction zone was constrained by mineral assemblage of garnet-omphacite from FMQ-1.9 to FMQ-2.5 at its metamorphic peak(maximum P-T) conditions.In comparison with redox conditions of other subduction zones,Western Tianshan has the lowest oxygen fugacity.Graphite and light hydrocarbon inclusions were ubiqutously identified in Western Tianshan HP metamorphic rocks and speculated to be formed from reduction of Fe-carbonate at low redox condition,which is also confirmed by high-pressure experimental simulation.Based on petrological observation and high-pressure simulation,a polarized redox model of reducing slab but oxidizing mantle wedge in subduction zone is proposed,and its effect on deep carbon cycle in subduction zones is further discussed.展开更多
The general classification of intermediate-acid intrusive rocks in the metamorphic zone of Gaoligong Mountains as one of the metamorphic terranes of Proterozoic Gaoligong Mountains is problematic regarding the intrusi...The general classification of intermediate-acid intrusive rocks in the metamorphic zone of Gaoligong Mountains as one of the metamorphic terranes of Proterozoic Gaoligong Mountains is problematic regarding the intrusion stage and age, as well as the subsequent metamorphism and deformation. In this study, we investigated granitic gneiss in the metamorphic zone of Gaoligong Mountains based on the 1：50,000 regional geological survey of Qushi Street （2011-2013） and SHRIMP U-Pb zircon geochronology. Results showed that the SHRIMP U-Pb zircon dating of granitic gneiss ranged from 163.5±5.7 Ma to 74.0±2.0 Ma. Thus, the granitic gneiss was grouped into orthometamorphic rocks （metamorphic intrusions）. The dating data of granite rocks associated with intense metamorphism and deformation were divided into three groups, 163.5±5.7 to 162.3±3.1 Ma, 132.2-101.0 Ma and 99.4±3.5-74.0±2.0 Ma, which respectively represented three independent geologic events including an important magma intrusion with superimposed metamorphic effects in the late Middle Jurassic, regional dynamic metamorphism and superimposed reformation of fluid action in the early Cretaceous, and dynamic metamorphism dominated by ductile shear and metamorphism starting from the late Cretaceous.展开更多
This paper, by applying the theories of landscape ecology, illustrates the role and mechanism of windbreak system in the establishment and maintenance of oasis ecosystem on the basis of systematic analysis of characte...This paper, by applying the theories of landscape ecology, illustrates the role and mechanism of windbreak system in the establishment and maintenance of oasis ecosystem on the basis of systematic analysis of characteristics and ecological crises of China's desert, and especially of desert zone in western China. Furthermore, direct economic benefits are summarized.展开更多
文摘Yushenfu mining area is located in an ecological fragile area in western China, the coal seam of which is the Jurassic Ysn'an Foirnalion. The Jurassic Yan'an Formation con tains five minable coal seams, the top layer of which is thick, covered by shallow overburden and located under aquifers. Therefore, the mining induced water flowing fractured zone can easily extend to the aquifers of both the Quaternary Sarahu and Jurassic Zhiluo Formation. This would result in a series of negative hydrological and ecological effects, including groundwater leakage, groundwater lowering, furtherly causing surface vegetation withering and dying, surface water body reduction, spring drying out, and water flow of river being decreased substantially. To solve these environmental problems, several technologies have been carried out by Chinese scientists, one of which is water-preserved coal mining. This paper presents a review of the origin, definition and development of water-preserved coal mining, and its applications in Yushenfu mining area. The applicable conditions, research contents, research methodology, and technical foundation of water-preserved coal mining are addressed in this paper. The future research focuses regarding water-preserved coal mining in China are also discussed in this paper. Its results serve as a guide for selecting the methods to be preferred for mining in case the geological conditions, roof overburden structure and coal mining process are similar to Yushenfu mining area.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41574074, 41174085, 41430319)the Innovation Team Project of Chinese Academy of Sciences (Grant No. KZZD-EW-TZ-19)the Strategic Pilot Technology of Chinese Academy of Sciences (Grant No. XDA1103010102)
文摘The western Sichuan hydrothermal area is located at the northeastern margin of the eastern syntaxis of the Qinghai-Tibet Plateau, which is also the eastern end of the Mediterranean-Himalayan geothermal activity zone. There are 248 warm or hot springs in this area, and 11 have temperatures beyond the local boiling temperature. Most of these hot springs are distributed along the Jinshajiang, Dege-Xiangcheng, Ganzi-Litang, and Xianshuihe faults, forming a NW-SE hydrothermal belt. A geothermal analysis of this high-temperature hydrothermal area is an important basis for understanding the deep geodynamic process of the eastern syntaxis of the Qinghai-Tibet Plateau. In addition, this study offers an a priori view to utilize geothermal resources, which is important in both scientific research and application. We use gravity, magnetic, seismic, and helium isotope data to analyze the crust-mantle heat flow ratio and deep geothermal structure. The results show that the background terrestrial heat flow descends from southwest to northeast. The crustal heat ratio is not more than 60%. The high temperature hydrothermal active is related to crustal dynamics processes. Along the Batang-Litang-Kangding line, the Moho depth increases eastward, which is consistent with the changing Qc/Qm(crustal/mantle heat flow) ratio trend. The geoid in the hydrothermal zone is 4–6 km higher than the surroundings, forming a local "platform". The NW-SE striking local tensile stress zone and uplift structure in the upper and middle crust corresponds with the surface hydrothermal active zone. There is an average Curie Point Depth(CPD) of 19.5–22.5 km in Batang, Litang, and Kangding. The local shear-wave(S-wave) velocity is relatively low in the middle and lower crust. The S-wave shows a low velocity trap(Vs<3.2 km s.1) at 15–30 km, which is considered a high-temperature partial melting magma, the crustal source of the hydrothermal active zone. We conclude that the hydrothermal system in this area can be divided into Batang-type and Kangding-t
基金co-supported by the National Natural Science Foundation of China(grant No.41302070)the Fundamental Research Funds for the Central Universities (grants No.310827172004 and 310827173401)Geological Exploration Fund Project of Qinghai Province (grant No.2012209)
文摘Objective Eclogites are important indicators of ancient plate boundaries or paleosuture zones. Despite their great geological significance, very few investigations have been carried out in the Kunlun region. The Central East Kunlun fault zone was believed to be an Early Paleozoic suture zone, but there has been no reliable evidence for this, though studies on ophiolite, granite, and basic granulite indicate that the Early Paleozoic orogeny occurred in the East Kunlun. This work focused on the Dagele eclogites in Central East Kunlun to provide new constraints for the Central East Kunlun suture zone.
基金support from the National Natural Science Foundation of China(Grant No.42276049)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB42020103).
文摘Recent seismic evidence shows that basalt accumulation is widespread in the mantle transition zone(MTZ),yet its ubiquity or sporadic nature remains uncertain.To investigate this phenomenon further,we characterized the velocity structure across the 660-km discontinuity that separates the upper mantle from the lower mantle beneath the Sea of Okhotsk by modeling the waveform of the S660P phase,a downgoing S wave converting into a P wave at the 660-km interface.These waves were excited by two regional>410-km-deep events and were recorded by stations in central Asia.Our findings showed no need to introduce velocity anomalies at the base of the MTZ to explain the S660P waveforms because the IASP91 model adequately reproduced the waveforms.This finding indicates that the basalt accumulation has not affected the bottom of the MTZ in the study area.Instead,this discontinuity is primarily controlled by temperature or water content variations,or both.Thus,we argue that the basalt accumulation at the base of the MTZ is sporadic,not ubiquitous,reflecting its heterogeneous distribution.
文摘Detailed work on Quaternary volcanism has been carried out in the Mermoz and Fann sectors of western Senegal. In the Mermoz sector, the main emission zone is a collapsed crater located at the intersection of three major fractures: NE-SW, NW-SE and N-S. The lithological succession in this Mermoz sector comprises, from bottom to top: 1) a substratum with at its base Eocene limestones on which lie Quaternary sands surmounted by stratified tuffs;2) a vesicular ball dolerite which deforms the stratified tuffs;3) a dark early breccia;4) two generations of basanites: the first is vesicular, the second non-vesicular;5) a clear intermediate breccia and finally 6) a late breccia. The Fann sector contains several emission zones, most of which are currently located in the ocean. The lavas may have reached the coast through E-W and NE-SW faults. The lithological succession includes from bottom to top: 1) scoria-rich early volcanic breccias;2) a first generation of non-vesicular mesocrate dolerite (D1);3) a second generation of melanocrate vesicular dolerite (D2);4) basanites and finally 5) a late breccia. The geochemical characteristics of the lavas studied are compatible with a very enriched and very deep magmatic source of the garnet lherzolite type located in the lower mantle. The magma from this source would have risen in the form of mantle plumes through major NE-SW and E-W faults in a continental intraplate context.
基金Sub-global project of UN Millennium Ecosystem Assessment (MA) programkey project of international scientific+1 种基金technological collaboration funded by the Ministry of S & T P. R. China the Knowledge Innovation Project of CAS No.ZCX02-308.
文摘The objectives of Integrated Ecosystem Assessment for Western Development of China includes: (1) providing scientific basis for ecosystem protection, ecosystem management and ecological construction in the western development; (2) developing complete database and analytical tools and strengthening decision-making support capacity; and (3) improving ecosystem management in China, spreading ecological knowledge to the public, serving decision-making of local and central governments, and promoting socio-economic sustainable development. The design and implementation of the project are of significance under the macro background of western development of China. By the integrated assessment of western China, we can get the first-hand data covering all the environmental factors as well as disclose the situations and their changing trends of ecosystem in the western part of China, which will benefit the decision-making for the central and local governments in the implementation of the western development strategy. In other words, the implementation of the project, to a certain extent, can guarantee the regional sustainable development of western China.
基金supported by the National Natural Science Foundation of China (Grant Nos. 91858212, 91858214, and 41906056)。
文摘The Neogene is an important period for studying the onset of subduction,with numerous subduction zones forming in the western Pacific,including the Ryukyu,Manila,Philippine,North Sulawesi,Halmahera,New Britain,Solomon,and New Hebrides subduction zones.However,studies on these subduction zones are relatively independent,so it is important to conduct systematic comparative studies.In this paper,we review the initiation models of Neogene subduction in the western Pacific,with the three typical types of subduction initiation models including polarity-reversal,induced subduction re-initiation,and noninherited subduction initiation to form new ruptures.In addition,the parameters of different subduction zones are collated to form five categories:basic features,subducting plate features,upper plate features,kinematic features,and subsequent activity.The regularity of the subduction processes,the specificity of the different subduction cases,and the possible constraints between the subduction initiation types and the characteristics of the subduction zone parameters are discussed and analyzed.The compiled dataset of the subduction zone parameters can provide data support for related studies.
基金supported by the NSF of China(Grant No.41520104004)。
文摘Knowing the phase relations of carbon-bearing phases at high-pressure(HP) and high-temperature(HT) condition is essential for understanding the deep carbon cycle in the subduction zones.In particular,the phase relation of carbon-bearing phases is also strongly influenced by redox condition of subduction zones,which is poorly explored.Here we summarized the phase relations of carbon-bearing phases(calcite,aragonite,dolomite,magnesite,graphite,hydrocarbon) in HP metamorphic rocks(marble,metapelite,eclogite) from the Western Tianshan subduction zone and high-pressure experiments.During prograde progress of subduction,carbonates in altered oceanic crust change from Ca-carbonate(calcite) to Ca,Mg-carbonate(dolomite),then finally to Mgcarbonate(magnesite) via Mg-Ca cation exchange reaction between silicate and carbonate,while calcite in sedimentary calcareous ooze on oceanic crust directly transfers to high-pressure aragonite in marble or amorphous CaCO3 in subduction zones.Redox evolution also plays a significant effect on the carbon speciation in the Western Tianshan subduction zone.The prograde oxygen fugacity of the Western Tianshan subduction zone was constrained by mineral assemblage of garnet-omphacite from FMQ-1.9 to FMQ-2.5 at its metamorphic peak(maximum P-T) conditions.In comparison with redox conditions of other subduction zones,Western Tianshan has the lowest oxygen fugacity.Graphite and light hydrocarbon inclusions were ubiqutously identified in Western Tianshan HP metamorphic rocks and speculated to be formed from reduction of Fe-carbonate at low redox condition,which is also confirmed by high-pressure experimental simulation.Based on petrological observation and high-pressure simulation,a polarized redox model of reducing slab but oxidizing mantle wedge in subduction zone is proposed,and its effect on deep carbon cycle in subduction zones is further discussed.
基金part of the 1:50000 regional geological surveys of Qushi Sheet, Daqie Street and Dadong Street carried out in 2004 and financially supported by the National Program on Key BasicResearch Project of China (973 Program)(No.2009CB421007)
文摘The general classification of intermediate-acid intrusive rocks in the metamorphic zone of Gaoligong Mountains as one of the metamorphic terranes of Proterozoic Gaoligong Mountains is problematic regarding the intrusion stage and age, as well as the subsequent metamorphism and deformation. In this study, we investigated granitic gneiss in the metamorphic zone of Gaoligong Mountains based on the 1：50,000 regional geological survey of Qushi Street （2011-2013） and SHRIMP U-Pb zircon geochronology. Results showed that the SHRIMP U-Pb zircon dating of granitic gneiss ranged from 163.5±5.7 Ma to 74.0±2.0 Ma. Thus, the granitic gneiss was grouped into orthometamorphic rocks （metamorphic intrusions）. The dating data of granite rocks associated with intense metamorphism and deformation were divided into three groups, 163.5±5.7 to 162.3±3.1 Ma, 132.2-101.0 Ma and 99.4±3.5-74.0±2.0 Ma, which respectively represented three independent geologic events including an important magma intrusion with superimposed metamorphic effects in the late Middle Jurassic, regional dynamic metamorphism and superimposed reformation of fluid action in the early Cretaceous, and dynamic metamorphism dominated by ductile shear and metamorphism starting from the late Cretaceous.
文摘This paper, by applying the theories of landscape ecology, illustrates the role and mechanism of windbreak system in the establishment and maintenance of oasis ecosystem on the basis of systematic analysis of characteristics and ecological crises of China's desert, and especially of desert zone in western China. Furthermore, direct economic benefits are summarized.
