2020 Vol. 45, No. 12
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2020, 45(12): 4267-4290.
doi: 10.3799/dqkx.2020.315
Abstract:
One of the key tasks in geological survey is to establish the chronostratigraphic and lithostratigraphic sequences among different tectonic regions,forming fundamental for explorations of mineral energy,hydrological environment and engineering geology.Here it emphasize the primary controlling roles of structure,sedimentation and climatic environment in stratigraphic development,and proposes a definition for regional tectonostratigraphic divisions of different geological periods in China on the basis of comprehensive analyses and comparison of tectonic environment,sedimentary and climatic background,rock combination,palaeontological assemblage,geophysics and geochemical characteristics among those regional divisions. It applied this method to the strata of Cambrian Period for China as an example,and identified eleven distinguishing criteria for regional tectonostratigraphic divisions in China,they are as follows:global paleogeographic characteristics,stratigraphic- sedimentary types,major stratigraphic sequence of the basement and cover,timing of the ocean-continent transition,contact relationship of stratigraphic sequence,stratigraphic lithology and lithofacies of blocks,distribution and characteristics between main suture zone and subordinate suture zone,biogeography,tectonic lithofacies,paleogeographic pattern,paleoclimate division,and the feature of the division boundary.
One of the key tasks in geological survey is to establish the chronostratigraphic and lithostratigraphic sequences among different tectonic regions,forming fundamental for explorations of mineral energy,hydrological environment and engineering geology.Here it emphasize the primary controlling roles of structure,sedimentation and climatic environment in stratigraphic development,and proposes a definition for regional tectonostratigraphic divisions of different geological periods in China on the basis of comprehensive analyses and comparison of tectonic environment,sedimentary and climatic background,rock combination,palaeontological assemblage,geophysics and geochemical characteristics among those regional divisions. It applied this method to the strata of Cambrian Period for China as an example,and identified eleven distinguishing criteria for regional tectonostratigraphic divisions in China,they are as follows:global paleogeographic characteristics,stratigraphic- sedimentary types,major stratigraphic sequence of the basement and cover,timing of the ocean-continent transition,contact relationship of stratigraphic sequence,stratigraphic lithology and lithofacies of blocks,distribution and characteristics between main suture zone and subordinate suture zone,biogeography,tectonic lithofacies,paleogeographic pattern,paleoclimate division,and the feature of the division boundary.
2020, 45(12): 4291-4312.
doi: 10.3799/dqkx.2020.307
Abstract:
As the construction of ecological civilization has become the national goal,the regional geological survey must serve the security of energy and resources,the planning of land space,and the construction of ecological civilization. Presently,the regional geological survey has expanded to covered areas in China,such as plain,basin,grassland,desert,and so on. However,the current geological mapping technology and method system cannot meet the needs of the current work. It is urgent to explore new patterns and mapping technology and method systems and expand the service field of achievement. In 2014, China Geological Survey set up the "special geological and geomorphic area mapping pilot project",which explored and summarized the technology and method system of regional geological mapping in the covered area. Now,the mapping technology and method system of covered area with "technical method guide for regional geological survey in covered area (1:50 000)" as the core has formed. The framework of tectonic sedimentary evolution in eastern China since the Late Cenozoic has been preliminarily established,which reveals the constraints of the sedimentary process,the ecological environment evolution and the development of human civilization in eastern China since the Late Pleistocene. This technological system will be significant to lead the regional geological survey in the covered area,serve the national ecological civilization construction and ecological environment protection. The new mapping method system clearly puts forward to focus on national ecological civilization construction and ecological environment protection,take the earth system science as the theoretical basis of regional geological survey in the covered area,implement demand driven,problem-oriented and target assessment,and strive to solve the major basic geological issues,major resources and ecological environment issues in the survey area. The technical route is high integration of surface geological survey with various modern detection technologies and information technologies,and the importance of pre-research and design stage is emphasized. At the same time,it is necessary to stipulate the uneven workload,cancel the quantitative indicators of the main mapping work,innovate the expression of achievements,make clear that geological mapping serves a variety of social needs,advocate the chief mapping scientist responsibility system,and establish a regional survey mapping integrity system.
As the construction of ecological civilization has become the national goal,the regional geological survey must serve the security of energy and resources,the planning of land space,and the construction of ecological civilization. Presently,the regional geological survey has expanded to covered areas in China,such as plain,basin,grassland,desert,and so on. However,the current geological mapping technology and method system cannot meet the needs of the current work. It is urgent to explore new patterns and mapping technology and method systems and expand the service field of achievement. In 2014, China Geological Survey set up the "special geological and geomorphic area mapping pilot project",which explored and summarized the technology and method system of regional geological mapping in the covered area. Now,the mapping technology and method system of covered area with "technical method guide for regional geological survey in covered area (1:50 000)" as the core has formed. The framework of tectonic sedimentary evolution in eastern China since the Late Cenozoic has been preliminarily established,which reveals the constraints of the sedimentary process,the ecological environment evolution and the development of human civilization in eastern China since the Late Pleistocene. This technological system will be significant to lead the regional geological survey in the covered area,serve the national ecological civilization construction and ecological environment protection. The new mapping method system clearly puts forward to focus on national ecological civilization construction and ecological environment protection,take the earth system science as the theoretical basis of regional geological survey in the covered area,implement demand driven,problem-oriented and target assessment,and strive to solve the major basic geological issues,major resources and ecological environment issues in the survey area. The technical route is high integration of surface geological survey with various modern detection technologies and information technologies,and the importance of pre-research and design stage is emphasized. At the same time,it is necessary to stipulate the uneven workload,cancel the quantitative indicators of the main mapping work,innovate the expression of achievements,make clear that geological mapping serves a variety of social needs,advocate the chief mapping scientist responsibility system,and establish a regional survey mapping integrity system.
2020, 45(12): 4313-4331.
doi: 10.3799/dqkx.2020.300
Abstract:
Since the Mesozoic and Cenozoic,a series of rift basins are developed in the West China. The framework of the sedimentary covering layers in the basin as well as the basin-range coupling and tectonic topography evolution between the basin and surrounding mountains are critical for understanding the geodynamics. During the geological mapping works in the covered area,the sedimentary structure,boundary faults,deposit distribution and provenance of the basin could be analyzed by using geological,geophysical,geochemical and drilling methods. These techniques would help us getting a better understanding on the basin accumulation,mountain exhumation and tectonic topography evolution. Based on the geological mapping project in the Turpan-Hami basin,in this study it proposes and practices the methodologies for the analysis of basin-range coupling and tectonic topography evolution. After detailed geological mapping and analysis,the reginal gravity survey,magnetotelluric sounding,seismic profiling and drilling were performed in the study area. According to the geological observations and geophysical data,in this paper it analyzes and discusses the sediment frameworks in three dimensions,basin-controlled structures and erosion-deposition processes of the eastern Turpan-Hami basin,which contribute to the basin-range coupling and tectonic topography evolution in the eastern Tianshan. This work would provide a typical example for the analysis of basin-range coupling and tectonic topography evolution in covered area.
Since the Mesozoic and Cenozoic,a series of rift basins are developed in the West China. The framework of the sedimentary covering layers in the basin as well as the basin-range coupling and tectonic topography evolution between the basin and surrounding mountains are critical for understanding the geodynamics. During the geological mapping works in the covered area,the sedimentary structure,boundary faults,deposit distribution and provenance of the basin could be analyzed by using geological,geophysical,geochemical and drilling methods. These techniques would help us getting a better understanding on the basin accumulation,mountain exhumation and tectonic topography evolution. Based on the geological mapping project in the Turpan-Hami basin,in this study it proposes and practices the methodologies for the analysis of basin-range coupling and tectonic topography evolution. After detailed geological mapping and analysis,the reginal gravity survey,magnetotelluric sounding,seismic profiling and drilling were performed in the study area. According to the geological observations and geophysical data,in this paper it analyzes and discusses the sediment frameworks in three dimensions,basin-controlled structures and erosion-deposition processes of the eastern Turpan-Hami basin,which contribute to the basin-range coupling and tectonic topography evolution in the eastern Tianshan. This work would provide a typical example for the analysis of basin-range coupling and tectonic topography evolution in covered area.
2020, 45(12): 4332-4351.
doi: 10.3799/dqkx.2020.316
Abstract:
Storage,migration and differentiation of granitic magma in the crust are the basic processes leading to the growth and evolution of continental crust. Studies of magma storage and assembly in the crust over the past decade have challenged traditionally-held views of magma chambers as large,molten melt bodies. Geophysical exploration,petrological and mineralogical studies,and thermal history simulations in active volcanic areas have consistently demonstrated that the material in magma reservoirs is mainly crystal mush residing under sub-solidus temperature conditions for a long time and remaining in relatively cold storage. The large plutons outcropping on the surface today represent fossil magma reservoirs. Most of them were formed by multiple additions and incremental assembly of magma over a span of millions of years or even longer. The incremental assembly of plutons can be proved by observation of contact relationships between intrusive units,heterogeneity of rock and mineral compositions,and large timescales of pluton emplacement. The intrusion of large plutons in a shallow crust and large-volume volcanic eruptions require the existence of transcrustal magma plumbing systems in which magma is connected by a series of dykes to magma reservoirs at different depths,and huge stocks and batholiths are assembled by stacking of numerous sills.The existence of highly-fractionated granites and high-silica rhyolites,and especially the phenomena of super-eruptions require the reactivation and differentiation of crystal mush in magma reservoirs. The disaggregation of crystal mush is often due to a fresh magma intrusion from below injecting additional heat and fluid. The crystal cargo can provide clues to the pluton assembly,crystal mush rejuvenation and magma differentiation. In particular,antecrysts can provide new insights into the evolution of magma plumbing systems. In future,the study of granitic petrogenesis will focus on crystal mush rejuvenation and magma differentiation,the mechanisms of magma rise and assembly,the genetic relationships between volcanic rocks and intrusive rocks,and interdisciplinary research on magma plumbing systems,in order to construct a new paradigm for the study of granitic magma processes,and in-depth understanding of the growth and evolution mechanisms of continental crust.
Storage,migration and differentiation of granitic magma in the crust are the basic processes leading to the growth and evolution of continental crust. Studies of magma storage and assembly in the crust over the past decade have challenged traditionally-held views of magma chambers as large,molten melt bodies. Geophysical exploration,petrological and mineralogical studies,and thermal history simulations in active volcanic areas have consistently demonstrated that the material in magma reservoirs is mainly crystal mush residing under sub-solidus temperature conditions for a long time and remaining in relatively cold storage. The large plutons outcropping on the surface today represent fossil magma reservoirs. Most of them were formed by multiple additions and incremental assembly of magma over a span of millions of years or even longer. The incremental assembly of plutons can be proved by observation of contact relationships between intrusive units,heterogeneity of rock and mineral compositions,and large timescales of pluton emplacement. The intrusion of large plutons in a shallow crust and large-volume volcanic eruptions require the existence of transcrustal magma plumbing systems in which magma is connected by a series of dykes to magma reservoirs at different depths,and huge stocks and batholiths are assembled by stacking of numerous sills.The existence of highly-fractionated granites and high-silica rhyolites,and especially the phenomena of super-eruptions require the reactivation and differentiation of crystal mush in magma reservoirs. The disaggregation of crystal mush is often due to a fresh magma intrusion from below injecting additional heat and fluid. The crystal cargo can provide clues to the pluton assembly,crystal mush rejuvenation and magma differentiation. In particular,antecrysts can provide new insights into the evolution of magma plumbing systems. In future,the study of granitic petrogenesis will focus on crystal mush rejuvenation and magma differentiation,the mechanisms of magma rise and assembly,the genetic relationships between volcanic rocks and intrusive rocks,and interdisciplinary research on magma plumbing systems,in order to construct a new paradigm for the study of granitic magma processes,and in-depth understanding of the growth and evolution mechanisms of continental crust.
2020, 45(12): 4352-4369.
doi: 10.3799/dqkx.2020.122
Abstract:
Paleogene is one of the key intervals in the earth history and a critical period of many biotic and geologic events,including the collision between Indian and Eurasian plates as the resultant formation of the Tibetan plateau,the westward subduction of the Pacific plate beneath Eurasian plate and the accompanying large scale back-arc rifting,the Paleocene-Eocene thermal maximum and Eocene-Oligocene climate transition,and rapid radiation of mammals and angiosperms,etc. Thus,it is of great significance to establish the Paleogene tectonic-stratigraphic divisions and stratigraphic correlation framework in China,which is the cornerstone of further study on the coupling evolution of lithosphere,hydrosphere,atmosphere and biosphere of the earth in the Paleogene. Paleogene tectonic-stratigraphic divisions in China mainly reflects the division of the first and second-order tectonic-stratigraphic units and the tectonic background and distribution characteristics of the main basins in each unit. Through the comprehensive study of Paleogene tectonics,sedimentary basins (groups),volcanic rocks,uplifting belts and large deformation structures in China,10 first-order tectonic-stratigraphic units (super-realms) and 27 second-order tectonic-stratigraphic units (realms) are devised,including 129 basins. Through the research of the types of basins in each unit and their characteristics of tectonic settings,sedimentary sequence and stratigraphic contact,the Paleogene stratigraphic correlation framework in China and summarized the sedimentary-tectonic history is established.
Paleogene is one of the key intervals in the earth history and a critical period of many biotic and geologic events,including the collision between Indian and Eurasian plates as the resultant formation of the Tibetan plateau,the westward subduction of the Pacific plate beneath Eurasian plate and the accompanying large scale back-arc rifting,the Paleocene-Eocene thermal maximum and Eocene-Oligocene climate transition,and rapid radiation of mammals and angiosperms,etc. Thus,it is of great significance to establish the Paleogene tectonic-stratigraphic divisions and stratigraphic correlation framework in China,which is the cornerstone of further study on the coupling evolution of lithosphere,hydrosphere,atmosphere and biosphere of the earth in the Paleogene. Paleogene tectonic-stratigraphic divisions in China mainly reflects the division of the first and second-order tectonic-stratigraphic units and the tectonic background and distribution characteristics of the main basins in each unit. Through the comprehensive study of Paleogene tectonics,sedimentary basins (groups),volcanic rocks,uplifting belts and large deformation structures in China,10 first-order tectonic-stratigraphic units (super-realms) and 27 second-order tectonic-stratigraphic units (realms) are devised,including 129 basins. Through the research of the types of basins in each unit and their characteristics of tectonic settings,sedimentary sequence and stratigraphic contact,the Paleogene stratigraphic correlation framework in China and summarized the sedimentary-tectonic history is established.
2020, 45(12): 4370-4388.
doi: 10.3799/dqkx.2020.313
Abstract:
The Baishahe Formation in the lower part of the Jinshuikou Group is one of the basement metamorphic rock series in the East Kunlun,which has essential geological significance for studying the formation and evolution of the East Kunlun orogenic belt. In this paper,the Baishahe Formation exposed in the Nuomuhong area of Qinghai Province was selected as the object of study,which was investigated by geological field survey,petrology,whole-rock geochemistry,zircon U-Pb chronology,etc. The Baishahe rock group in the area was divided into three lithologic sections through investigation. Characteristic metamorphic mineral combinations such as sillimanite,garnet,monoclinic pyroxene,and dolomite were identified. This indicats that the rock group had experienced high amphibolite facies-low granulite facies metamorphism. For the identified argillaceous metamorphic rocks,the apparent peak metamorphic temperature and pressure recovered by the garnet-biotite thermometer and garnet-biotite-plagioclase-quartz manometer are 660-683 ℃,and 3.9-4.2 kbar,respectively. For basic metamorphic rocks,the metamorphic temperature and temperature recovered using hornblende-plagioclase thermometer and hornblende-plagioclase-quartz manometer are 723-772 ℃ and 3.4-4.9 kbar,respectively. The paragneiss was studied using clastic zircon chronology. Results show that the frequency peak concentrated at 1 300 Ma,and the original rock sedimentation age should be later than the Mesoproterozoic. The original rocks were recovered using rock geochemical data. The original rocks of the basic metamorphic rock in the Baishahe Formation were determined to be tholeiitic basalt formed in the extensional environment within the plate; the original rocks of the felsic metamorphic rock were identified as muddy-sand continental marginal clastic rock. The original rocks of the Baishahe Formation are constructed of continental marginal clastic rocks with basic volcanic rocks,with carbonate deposits in the upper part. It may have been formed in the late stage of continental rifting and under the tectonic environments from extension to compression.
The Baishahe Formation in the lower part of the Jinshuikou Group is one of the basement metamorphic rock series in the East Kunlun,which has essential geological significance for studying the formation and evolution of the East Kunlun orogenic belt. In this paper,the Baishahe Formation exposed in the Nuomuhong area of Qinghai Province was selected as the object of study,which was investigated by geological field survey,petrology,whole-rock geochemistry,zircon U-Pb chronology,etc. The Baishahe rock group in the area was divided into three lithologic sections through investigation. Characteristic metamorphic mineral combinations such as sillimanite,garnet,monoclinic pyroxene,and dolomite were identified. This indicats that the rock group had experienced high amphibolite facies-low granulite facies metamorphism. For the identified argillaceous metamorphic rocks,the apparent peak metamorphic temperature and pressure recovered by the garnet-biotite thermometer and garnet-biotite-plagioclase-quartz manometer are 660-683 ℃,and 3.9-4.2 kbar,respectively. For basic metamorphic rocks,the metamorphic temperature and temperature recovered using hornblende-plagioclase thermometer and hornblende-plagioclase-quartz manometer are 723-772 ℃ and 3.4-4.9 kbar,respectively. The paragneiss was studied using clastic zircon chronology. Results show that the frequency peak concentrated at 1 300 Ma,and the original rock sedimentation age should be later than the Mesoproterozoic. The original rocks were recovered using rock geochemical data. The original rocks of the basic metamorphic rock in the Baishahe Formation were determined to be tholeiitic basalt formed in the extensional environment within the plate; the original rocks of the felsic metamorphic rock were identified as muddy-sand continental marginal clastic rock. The original rocks of the Baishahe Formation are constructed of continental marginal clastic rocks with basic volcanic rocks,with carbonate deposits in the upper part. It may have been formed in the late stage of continental rifting and under the tectonic environments from extension to compression.
2020, 45(12): 4389-4398.
doi: 10.3799/dqkx.2020.337
Abstract:
The ore-accumulating structural system is a composite structural system which controls the migration and enrichment of ore-forming materials. The ore-accumulating structural systems can be divided into four genetic types: magmatic deposit structural system,magmatic hydrothermal deposit structural system,sedimentary-hydrothermal sedimentary deposit structural system and metamorphic deposit structural system. In this paper,the characteristics and ore-controlling regularities of the ore-accumulating structural systems for the skarn Fe-Cu deposits,porphyry and porphyry-skarn Cu-Mo deposits,magmatic hydrothermal W-Sn deposits,magmatic mesothermal-epithermal Au-polymetallic deposits,and hydrothermal sedimentary-reworked Pb-Zn deposits are discussed. it summarizes the indicators and favorable positions for ore-accumulating structures,and proposes the effective ways to explore concealed ore deposits (orebodies) through the study of ore-accumulating structures combining the geological,geophysical and geochemical methods as well as the analogy-seeking anomaly thoughts,and provides some examples for reference.
The ore-accumulating structural system is a composite structural system which controls the migration and enrichment of ore-forming materials. The ore-accumulating structural systems can be divided into four genetic types: magmatic deposit structural system,magmatic hydrothermal deposit structural system,sedimentary-hydrothermal sedimentary deposit structural system and metamorphic deposit structural system. In this paper,the characteristics and ore-controlling regularities of the ore-accumulating structural systems for the skarn Fe-Cu deposits,porphyry and porphyry-skarn Cu-Mo deposits,magmatic hydrothermal W-Sn deposits,magmatic mesothermal-epithermal Au-polymetallic deposits,and hydrothermal sedimentary-reworked Pb-Zn deposits are discussed. it summarizes the indicators and favorable positions for ore-accumulating structures,and proposes the effective ways to explore concealed ore deposits (orebodies) through the study of ore-accumulating structures combining the geological,geophysical and geochemical methods as well as the analogy-seeking anomaly thoughts,and provides some examples for reference.
2020, 45(12): 4399-4427.
doi: 10.3799/dqkx.2020.995
Abstract:
As breakthrough achieved in recent exploration,lead-zinc polymetallic deposits in the Great Xing'an Range have shown complexity and differences in aspects of mineralized elements,temporal-spatial distribution,genesis and so on. For a further inspection of the variation and its internal causes,data from medium-large sized deposits are compiled and compared in this study. Main conclusions are summarized: (1) these deposits formed three parallel NE trending belts with a higher intensity in the southern belt; (2) two major phases of mineralization are recognized as in the Middle-Late Triassic (less important) and the predominant Late Jurassic-Early Cretaceous,superimposed mineralization is also notable; (3) epithermal deposit is representative in the northern belt,while skarn- and magmatic hydrothermal vein-types are more common in the middle and the southern belts; (4) under the Late Jurassic-Early Cretaceous extensional environment,enormous acidic-intermediate magma emplacement affected the whole Great Xing'an Range,leading to the formation of various lead-zinc polymetallic deposits,among which tin-rich ones in the southern belt exhibit genetic links to highly differentiated magma; (5) strong spatial association between the fluorine-,manganese-related alteration and mineralization is noticed; (6) deposits in the northern,middle and southern belts have their sulfur sourced from genetically related volcanic-subvolcanic rocks,ore-related magma and a combination of magma and country rocks; (7) Pb isotope data indicate that most deposits have a mixed lead source from orogeny,probably due to similar regional post-orogenic background in the Late Jurassic-Early Cretaceous; (8) as suggested by H-O isotopic data,meteoric water contributes more for fluid source in epithermal deposits,despite a more crucial role of magmatic water in skarn- and magmatic hydrothermal vein-type deposits.
As breakthrough achieved in recent exploration,lead-zinc polymetallic deposits in the Great Xing'an Range have shown complexity and differences in aspects of mineralized elements,temporal-spatial distribution,genesis and so on. For a further inspection of the variation and its internal causes,data from medium-large sized deposits are compiled and compared in this study. Main conclusions are summarized: (1) these deposits formed three parallel NE trending belts with a higher intensity in the southern belt; (2) two major phases of mineralization are recognized as in the Middle-Late Triassic (less important) and the predominant Late Jurassic-Early Cretaceous,superimposed mineralization is also notable; (3) epithermal deposit is representative in the northern belt,while skarn- and magmatic hydrothermal vein-types are more common in the middle and the southern belts; (4) under the Late Jurassic-Early Cretaceous extensional environment,enormous acidic-intermediate magma emplacement affected the whole Great Xing'an Range,leading to the formation of various lead-zinc polymetallic deposits,among which tin-rich ones in the southern belt exhibit genetic links to highly differentiated magma; (5) strong spatial association between the fluorine-,manganese-related alteration and mineralization is noticed; (6) deposits in the northern,middle and southern belts have their sulfur sourced from genetically related volcanic-subvolcanic rocks,ore-related magma and a combination of magma and country rocks; (7) Pb isotope data indicate that most deposits have a mixed lead source from orogeny,probably due to similar regional post-orogenic background in the Late Jurassic-Early Cretaceous; (8) as suggested by H-O isotopic data,meteoric water contributes more for fluid source in epithermal deposits,despite a more crucial role of magmatic water in skarn- and magmatic hydrothermal vein-type deposits.
2020, 45(12): 4428-4445.
doi: 10.3799/dqkx.2020.298
Abstract:
The Huanggang iron-tin polymetallic deposit in the southern Great Xing'an Range is characterized by alteration-mineralization features, which is of great significance to study the ore-forming process of skarn deposit. In this paper, it makes the Electron Probe Micro-analysis (EPMA) on typical alteration minerals and metallic minerals. The results indicate that hydrothermal evolution in the study area has experienced four stages. The prograde skarn stage (Ⅰ): the minerals are mainly grossular (GrtⅡ) with the andradite (GrtⅠ) core and hedenbergite. The retrograde skarn stage (Ⅱ): the minerals are mainly Fe-rich garnet (GrtⅢ), disseminated magnetite and hydrated minerals. The oxide stage (Ⅲ): the minerals are represented by a large amount of magnetite, cassiterite, a small amount of andradite (GrtⅣ) and diopside. The sulfide stage (Ⅳ): the minerals are a small amount of magnetites which are replaced by later sulfides, developing arsenopyrite, pyrite, chalcopyrite, iron-rich sphalerite, light-colored sphalerite-chalcopyrite-isostannite solid solution, and antimony-bearing tetrahedrite. It makes clear that the source of main metallogenic stage from the Huanggang skarn iron polymetallic deposit is magmatic fluid, metasomatic fluid to mixing of meteoric water, fluid compositions change complex, fluid evolution is characterized by the temperature decreased, the water/rock ratio increases gradually, and reducing to oxidizing to reducing.
The Huanggang iron-tin polymetallic deposit in the southern Great Xing'an Range is characterized by alteration-mineralization features, which is of great significance to study the ore-forming process of skarn deposit. In this paper, it makes the Electron Probe Micro-analysis (EPMA) on typical alteration minerals and metallic minerals. The results indicate that hydrothermal evolution in the study area has experienced four stages. The prograde skarn stage (Ⅰ): the minerals are mainly grossular (GrtⅡ) with the andradite (GrtⅠ) core and hedenbergite. The retrograde skarn stage (Ⅱ): the minerals are mainly Fe-rich garnet (GrtⅢ), disseminated magnetite and hydrated minerals. The oxide stage (Ⅲ): the minerals are represented by a large amount of magnetite, cassiterite, a small amount of andradite (GrtⅣ) and diopside. The sulfide stage (Ⅳ): the minerals are a small amount of magnetites which are replaced by later sulfides, developing arsenopyrite, pyrite, chalcopyrite, iron-rich sphalerite, light-colored sphalerite-chalcopyrite-isostannite solid solution, and antimony-bearing tetrahedrite. It makes clear that the source of main metallogenic stage from the Huanggang skarn iron polymetallic deposit is magmatic fluid, metasomatic fluid to mixing of meteoric water, fluid compositions change complex, fluid evolution is characterized by the temperature decreased, the water/rock ratio increases gradually, and reducing to oxidizing to reducing.
2020, 45(12): 4446-4462.
doi: 10.3799/dqkx.2020.317
Abstract:
In order to study the petrogenesis and tectonic setting of intermediate-felsic volcanics in Ta'erqi area, central Great Xing'an Range and promote the comparative study of Mesozoic volcanics in this region, in this paper it presents a synthesis study of zircon U-Pb chronology, geochemistry and Hf isotopes of volcanics from Manketouebo and Baiyingaolao formations. Zircon U-Pb dating yielded weighted mean ages of 154±2 Ma and 154±3 Ma of Manketouebo Formation and 132±2 Ma of Baiyingaolao Formation.The samples are weak peraluminous with high alkali, low Mg and Ca contents, while existing the enrichment of Rb, K, Zr, Hf and depletion of Eu, Sr, Ba, P, Ti with moderate to strong negative Eu anomalies. The average zirconium saturation temperature are 915 ℃ and 841 ℃, respectively, showing the characteristics of A-type rhyolite. The εHf(t) values range from +6.9 to +8.4 and +6.7 to +7.9, while the tDM2 values range from 624 Ma to 670 Ma and 611 Ma to 682 Ma, indicating that the magma originated from the the partial melting of Neoproterozoic young crust accreted from the depleted mantle. Manketouebo Formation in Ta'erqi area formed in the early stage of extensional tectonic setting after the closure of Mongolia-Okhotsk ocean, while Baiyingaolao Formation was caused by the lithosphere extension and delamination after the closure of the Mongolia-Okhotsk Ocean and the back-arc extension induced by the subduction of the paleo-Pacific plate to Eurasia.
In order to study the petrogenesis and tectonic setting of intermediate-felsic volcanics in Ta'erqi area, central Great Xing'an Range and promote the comparative study of Mesozoic volcanics in this region, in this paper it presents a synthesis study of zircon U-Pb chronology, geochemistry and Hf isotopes of volcanics from Manketouebo and Baiyingaolao formations. Zircon U-Pb dating yielded weighted mean ages of 154±2 Ma and 154±3 Ma of Manketouebo Formation and 132±2 Ma of Baiyingaolao Formation.The samples are weak peraluminous with high alkali, low Mg and Ca contents, while existing the enrichment of Rb, K, Zr, Hf and depletion of Eu, Sr, Ba, P, Ti with moderate to strong negative Eu anomalies. The average zirconium saturation temperature are 915 ℃ and 841 ℃, respectively, showing the characteristics of A-type rhyolite. The εHf(t) values range from +6.9 to +8.4 and +6.7 to +7.9, while the tDM2 values range from 624 Ma to 670 Ma and 611 Ma to 682 Ma, indicating that the magma originated from the the partial melting of Neoproterozoic young crust accreted from the depleted mantle. Manketouebo Formation in Ta'erqi area formed in the early stage of extensional tectonic setting after the closure of Mongolia-Okhotsk ocean, while Baiyingaolao Formation was caused by the lithosphere extension and delamination after the closure of the Mongolia-Okhotsk Ocean and the back-arc extension induced by the subduction of the paleo-Pacific plate to Eurasia.
2020, 45(12): 4463-4480.
doi: 10.3799/dqkx.2020.262
Abstract:
The Balong Ag-Sn polymetallic deposit was newly discovered in the volcanic rock area of western Gangdese by mineral resources investigation project. The surface ore bodies are vein type ore bodies controlled by the coupling of thrust belt, volcanic mechanism and secondary faults in the margin of volcano-sediment graben basins. In order to find out the genesis of Balong deposit, the zircon U-Pb geochronology, ore mineralogy, mineral geochemistry and S-Pb isotopes were carried out. The results show that the weighted average age of zircon LA-ICP-MS U-Pb is 126.5±1.2 Ma in the ore-bearing volcanic rocks, the mineral assemblage is mainly composed of medium-low temperature minerals and a small amount of medium-high temperature minerals, the Zn/Cd and Zn/Fe ratios of sphalerite are 321-17 407 and 2.4-4.4, the Co/Ni ratio of pyrite is 2.2-3.6, the δ 34S value of sulfide changes from 2.94 ‰ to 4.48 ‰, the 206Pb/204Pb ratio is 18.590-18.779, the 207Pb/204Pb ratio is 15.636-15.865, the 208Pb/204Pb ratio is 38.883-39.991.The above results show that the formation of the deposit is closely related to the subvolcanic hydrothermal fluid of the late stage of Early Cretaceous volcanic activity in the western Gangdese, and the ore-forming materials have the characteristics of magmatic sulfur and lead in the upper crust. Compared with the typical Ag-Sn polymetallic deposits in the world, the metallogenic characteristics of the Balong deposit are similar to those of the world's large-superlarge scale Ag-Sn polymetallic deposits. The surface ore body belongs to the epithermal silver-polymetallic orebody, and the porphyry tin-polymetallic orebody may develop downward. The metallogenic characteristics of Ag-rich and Sn-bearing deposit in the western Gangdese are firstly discovered. This discovery not only provides new data and constraints for the study of the genetic types of the deposits in the volcanic rock area of the western Gangdese, but also greatly broadens the prospecting horizon in the area.
The Balong Ag-Sn polymetallic deposit was newly discovered in the volcanic rock area of western Gangdese by mineral resources investigation project. The surface ore bodies are vein type ore bodies controlled by the coupling of thrust belt, volcanic mechanism and secondary faults in the margin of volcano-sediment graben basins. In order to find out the genesis of Balong deposit, the zircon U-Pb geochronology, ore mineralogy, mineral geochemistry and S-Pb isotopes were carried out. The results show that the weighted average age of zircon LA-ICP-MS U-Pb is 126.5±1.2 Ma in the ore-bearing volcanic rocks, the mineral assemblage is mainly composed of medium-low temperature minerals and a small amount of medium-high temperature minerals, the Zn/Cd and Zn/Fe ratios of sphalerite are 321-17 407 and 2.4-4.4, the Co/Ni ratio of pyrite is 2.2-3.6, the δ 34S value of sulfide changes from 2.94 ‰ to 4.48 ‰, the 206Pb/204Pb ratio is 18.590-18.779, the 207Pb/204Pb ratio is 15.636-15.865, the 208Pb/204Pb ratio is 38.883-39.991.The above results show that the formation of the deposit is closely related to the subvolcanic hydrothermal fluid of the late stage of Early Cretaceous volcanic activity in the western Gangdese, and the ore-forming materials have the characteristics of magmatic sulfur and lead in the upper crust. Compared with the typical Ag-Sn polymetallic deposits in the world, the metallogenic characteristics of the Balong deposit are similar to those of the world's large-superlarge scale Ag-Sn polymetallic deposits. The surface ore body belongs to the epithermal silver-polymetallic orebody, and the porphyry tin-polymetallic orebody may develop downward. The metallogenic characteristics of Ag-rich and Sn-bearing deposit in the western Gangdese are firstly discovered. This discovery not only provides new data and constraints for the study of the genetic types of the deposits in the volcanic rock area of the western Gangdese, but also greatly broadens the prospecting horizon in the area.
2020, 45(12): 4481-4497.
doi: 10.3799/dqkx.2020.245
Abstract:
A series of Permian mafic-ultramafic complexes associated with large and medium-sized Ni deposits have been found in recent decades in the Beishan area, Xinjiang, NW China. Based on the new data obtained from the geological survey, a few controversial scientific issues, such as geochronology, the origin and nature of parental magma, tectonic setting, sulfide immiscibility mechanism, etc., are redefined. Two episodes of mafic magmatism in the Beishan area were recognized. i.e. the Early Permian and Middle Permian (261-266 Ma). The parental magma may have originated from high degree partial melting of the depleted mantle which suffered from metasomatism and modification by subduction-related fluid in relatively shallow depth. It is characterized by high temperature, high Mg content, oxidized and hydrous nature. The Beishan mafic-ultramafic rocks are of non-plume origin, as well as of non-arc origin. The tectonic setting seems more likely slab break-off and consequent upwelling from an asthenosphere mantle in post-orogenic setting. The Pobei sub-belt and the Hongshishan sub-belt have similar rock types and geochemical features, but different mineralization types, suggesting multi-stages and differences of sulfide segregation mechanism. Addition of external S from adjacent VMS Cu deposits triggers sulfide segregation prior to olivine crystallization. Injection of ore pulp to later norite gives rise to vein-type mineralization with high Ni tenor. Finally, some indicators are proposed for the future prospecting, for example, relatively low Ni content in olivine from ultramafic rocks, high Mg but low Ti contents, high m/s and m/f ratios, tholeiitic parental magma (>11.5% MgO), relatively high degree of partial melting (>10%) and high solidification index (>50). The area along the Hongshijing deep fault is of further prospecting potential.
A series of Permian mafic-ultramafic complexes associated with large and medium-sized Ni deposits have been found in recent decades in the Beishan area, Xinjiang, NW China. Based on the new data obtained from the geological survey, a few controversial scientific issues, such as geochronology, the origin and nature of parental magma, tectonic setting, sulfide immiscibility mechanism, etc., are redefined. Two episodes of mafic magmatism in the Beishan area were recognized. i.e. the Early Permian and Middle Permian (261-266 Ma). The parental magma may have originated from high degree partial melting of the depleted mantle which suffered from metasomatism and modification by subduction-related fluid in relatively shallow depth. It is characterized by high temperature, high Mg content, oxidized and hydrous nature. The Beishan mafic-ultramafic rocks are of non-plume origin, as well as of non-arc origin. The tectonic setting seems more likely slab break-off and consequent upwelling from an asthenosphere mantle in post-orogenic setting. The Pobei sub-belt and the Hongshishan sub-belt have similar rock types and geochemical features, but different mineralization types, suggesting multi-stages and differences of sulfide segregation mechanism. Addition of external S from adjacent VMS Cu deposits triggers sulfide segregation prior to olivine crystallization. Injection of ore pulp to later norite gives rise to vein-type mineralization with high Ni tenor. Finally, some indicators are proposed for the future prospecting, for example, relatively low Ni content in olivine from ultramafic rocks, high Mg but low Ti contents, high m/s and m/f ratios, tholeiitic parental magma (>11.5% MgO), relatively high degree of partial melting (>10%) and high solidification index (>50). The area along the Hongshijing deep fault is of further prospecting potential.
2020, 45(12): 4498-4511.
doi: 10.3799/dqkx.2020.274
Abstract:
Around how to use the theories of Earth's Critical Zone (CZ) to resolve ecological environment protection problem of large basin, it defines the base level of erosion for basin as the bottom boundary of CZ in basin, based on the domestic and foreign research progress on CZ in combination with survey on CZ in central Yangtze River basin. It conducted the ecological environment problem library of basin, the variable library of four spheres for earth and the variable library of anthropogenic activities. Based on "four spheres for earth", "anthropogenic activities" and "time", it also constructed the six-dimensional matrix guided by typical ecological environment problems. It proposes that three horizontal-sections and five vertical-interfaces as structural model of CZ in basin, and also identify the common/feature variables of sections and interfaces. According to the above results, we establish preliminary theoretical approaches of survey on CZ in basin and conduct an exemplary research in Jianghan Plain, which breaks through traditional CZ research limitation due to relatively single study on small watershed, gradient of environmental variable and ecological environment problems. We also answer the question on "where to survey", "what to survey" and "what to monitor" of CZ in basin. This study provides a scientific basis for survey of CZ in Yangtze River basin and implementation of Yangtze River protection, and exploratory experiences for the establishment of theoretical approaches of survey on CZ in basin.
Around how to use the theories of Earth's Critical Zone (CZ) to resolve ecological environment protection problem of large basin, it defines the base level of erosion for basin as the bottom boundary of CZ in basin, based on the domestic and foreign research progress on CZ in combination with survey on CZ in central Yangtze River basin. It conducted the ecological environment problem library of basin, the variable library of four spheres for earth and the variable library of anthropogenic activities. Based on "four spheres for earth", "anthropogenic activities" and "time", it also constructed the six-dimensional matrix guided by typical ecological environment problems. It proposes that three horizontal-sections and five vertical-interfaces as structural model of CZ in basin, and also identify the common/feature variables of sections and interfaces. According to the above results, we establish preliminary theoretical approaches of survey on CZ in basin and conduct an exemplary research in Jianghan Plain, which breaks through traditional CZ research limitation due to relatively single study on small watershed, gradient of environmental variable and ecological environment problems. We also answer the question on "where to survey", "what to survey" and "what to monitor" of CZ in basin. This study provides a scientific basis for survey of CZ in Yangtze River basin and implementation of Yangtze River protection, and exploratory experiences for the establishment of theoretical approaches of survey on CZ in basin.
2020, 45(12): 4512-4523.
doi: 10.3799/dqkx.2020.261
Abstract:
In order to describe the structure and hydrological response mechanism of the karst water systems, the dispersion model, the diffusion model, the standard attenuation curve, and the Gaussian mixture models are presented for identifying the structure and explaining hydrological response. Successful application of these methods in the Y-M karst water system in the Three Gorges area shows that "single recharge-single discharge", "single recharge-multiple discharges" and "multiple recharge-single discharge" flow path patterns occurred in the area. After rainfalls, groundwater was dominated by convection in the response stage, while diffusion in the attenuation stage. The groundwater runoff components were divided into 5 and 6 grades for the rainy season and dry season, respectively. The conductivity and discharge thresholds dividing fast and slow flow were determined to be approximately 180 μS/cm and 0.6 m3/s, respectively, with fast flow exhibiting lower conductivity and larger discharge. On an quarterly basis, fast flow occurred 3.5% of the time and accounted for 19% of total water volume. The fast flow moved in the conduits, leading to the sharply variation of discharge and electrical conductivity, while the slow flow moved in the fissures and pores, which resulted in weak response. This study provides novel alternative methods for quantitative evaluation of structure and hydrological response of karst water systems.
In order to describe the structure and hydrological response mechanism of the karst water systems, the dispersion model, the diffusion model, the standard attenuation curve, and the Gaussian mixture models are presented for identifying the structure and explaining hydrological response. Successful application of these methods in the Y-M karst water system in the Three Gorges area shows that "single recharge-single discharge", "single recharge-multiple discharges" and "multiple recharge-single discharge" flow path patterns occurred in the area. After rainfalls, groundwater was dominated by convection in the response stage, while diffusion in the attenuation stage. The groundwater runoff components were divided into 5 and 6 grades for the rainy season and dry season, respectively. The conductivity and discharge thresholds dividing fast and slow flow were determined to be approximately 180 μS/cm and 0.6 m3/s, respectively, with fast flow exhibiting lower conductivity and larger discharge. On an quarterly basis, fast flow occurred 3.5% of the time and accounted for 19% of total water volume. The fast flow moved in the conduits, leading to the sharply variation of discharge and electrical conductivity, while the slow flow moved in the fissures and pores, which resulted in weak response. This study provides novel alternative methods for quantitative evaluation of structure and hydrological response of karst water systems.
2020, 45(12): 4524-4534.
doi: 10.3799/dqkx.2020.138
Abstract:
The Chaoshuidong Siphonal Spring () is in Yichang City, Hubei Province, which could still regularly intermittently flows out when there is no rain. Systematic research into the flow and hydrochemical dynamics and formation mechanisms of CSS is lacked. Based on long-term hydrological and meteorological observation data and hydrochemical test data, in this paper, it analyzes and summarizes the changes in the flow, water temperature and conductivity of the CSS at different times, and also analyzes the hydrochemical characteristics of the CSS karst water system. The CSS karst water system can be divided into the local water flow system of the Shilongdong Group and the intermediate water flow system of the Tianheban Group, and its dynamic characteristics can be divided into two distinct periods of rain and rain-free periods, which reflects the rapid response of karst water system to rainfall and the control function of karst siphon pipe to the intermediate water flow system of Tianheban Group, respectively.There are many intermittent flow out of multiple unstable cycles during the rain-free period. The source of intermittent discharge groundwater was identified by ion ratio method and the analysis of hydrodynamic features as the Tianheban Group rock aquifer, and with the increasing process flow, the proportion of deep-cycle groundwater reached 97%. Finally, combined with hydrogeological condition analysis, in the paper it summarizes the conceptual pattern map of water circulation in the CSS karst water system, and the development of the siphon pipe inside the gray rock aquifer of the Tianheban Group forms the characteristics of the water circulation during the rain and rain-free periodof the CSS.
The Chaoshuidong Siphonal Spring () is in Yichang City, Hubei Province, which could still regularly intermittently flows out when there is no rain. Systematic research into the flow and hydrochemical dynamics and formation mechanisms of CSS is lacked. Based on long-term hydrological and meteorological observation data and hydrochemical test data, in this paper, it analyzes and summarizes the changes in the flow, water temperature and conductivity of the CSS at different times, and also analyzes the hydrochemical characteristics of the CSS karst water system. The CSS karst water system can be divided into the local water flow system of the Shilongdong Group and the intermediate water flow system of the Tianheban Group, and its dynamic characteristics can be divided into two distinct periods of rain and rain-free periods, which reflects the rapid response of karst water system to rainfall and the control function of karst siphon pipe to the intermediate water flow system of Tianheban Group, respectively.There are many intermittent flow out of multiple unstable cycles during the rain-free period. The source of intermittent discharge groundwater was identified by ion ratio method and the analysis of hydrodynamic features as the Tianheban Group rock aquifer, and with the increasing process flow, the proportion of deep-cycle groundwater reached 97%. Finally, combined with hydrogeological condition analysis, in the paper it summarizes the conceptual pattern map of water circulation in the CSS karst water system, and the development of the siphon pipe inside the gray rock aquifer of the Tianheban Group forms the characteristics of the water circulation during the rain and rain-free periodof the CSS.
2020, 45(12): 4535-4549.
doi: 10.3799/dqkx.2020.247
Abstract:
The attribute interval numbers (AIN) in the frequency ratio analysis of continuous environmental factors and the landslide susceptibility model are two important uncertainties affecting the results of landslide susceptibility prediction (LSP). To study the effects of the two uncertain factors on the change rules of LSP, taking Shangyou County of Jiangxi Province, China, as study area, the AIN values of the continuous environmental factors are respectively set to be 4, 8, 12, 16 and 20. Meanwhile, five different data-based models (analytic hierarchy process (AHP), logistic regression (LR), BP neural network (BPNN), support vector machines (SVM) and random forests (RF)) are selected as LSP models. Hence, there are a total of 25 types of different calculation conditions for LSP. Finally, the accuracy and uncertainties of LSP are analyzed. The results show that: (1) For a certain model, the LSP accuracy gradually increases with the AIN value increasing from 4 to 8, then slowly increases to a stable level with AIN increasing from 8 to 20; (2) For a certain AIN, the LSP accuracy of the RF model is higher than SVM, followed by the BPNN, LR and AHP models; (3) Under all the 25 calculation conditions, the prediction accuracy of AIN=20 and RF model is the highest while that of AIN=4 and AHP model is the lowest, and the modeling efficiency and accuracy of AIN=8 and RF model are very high; (4) The landslide susceptibility indexes calculated by the higher AIN and more advanced machine learning models are more consistent with the actual distribution features of landslide probability and have relatively lower uncertainties. It can be concluded that an efficient and relatively accurate LSP model can be built under the condition of AIN value of 8 and RF model.
The attribute interval numbers (AIN) in the frequency ratio analysis of continuous environmental factors and the landslide susceptibility model are two important uncertainties affecting the results of landslide susceptibility prediction (LSP). To study the effects of the two uncertain factors on the change rules of LSP, taking Shangyou County of Jiangxi Province, China, as study area, the AIN values of the continuous environmental factors are respectively set to be 4, 8, 12, 16 and 20. Meanwhile, five different data-based models (analytic hierarchy process (AHP), logistic regression (LR), BP neural network (BPNN), support vector machines (SVM) and random forests (RF)) are selected as LSP models. Hence, there are a total of 25 types of different calculation conditions for LSP. Finally, the accuracy and uncertainties of LSP are analyzed. The results show that: (1) For a certain model, the LSP accuracy gradually increases with the AIN value increasing from 4 to 8, then slowly increases to a stable level with AIN increasing from 8 to 20; (2) For a certain AIN, the LSP accuracy of the RF model is higher than SVM, followed by the BPNN, LR and AHP models; (3) Under all the 25 calculation conditions, the prediction accuracy of AIN=20 and RF model is the highest while that of AIN=4 and AHP model is the lowest, and the modeling efficiency and accuracy of AIN=8 and RF model are very high; (4) The landslide susceptibility indexes calculated by the higher AIN and more advanced machine learning models are more consistent with the actual distribution features of landslide probability and have relatively lower uncertainties. It can be concluded that an efficient and relatively accurate LSP model can be built under the condition of AIN value of 8 and RF model.
2020, 45(12): 4550-4562.
doi: 10.3799/dqkx.2020.289
Abstract:
Applying the electrical resistivity tomography (ERT) technique in the marine environment claims higher levels in the aspects of instrument, measurement techniques, inversion and interpretation methods and so on. The exploration approaches on issues of geology, natural resources and environment will be further enriched by numerical simulations and actual measurement research of the marine ERT in the coastal area. Based on numerical simulations and field measurements, in this paper it focuses on the research of the resolution and spatial location of the typical geo-electrical models in the offshore area with different arrays such as dipole-dipole, Wenner and Schlumberger. It also studied the effects of seawater conductivity and first conducted two long profile measurements at the site of Pearl River Estuary in the Lingdingyang area. It shows that the detection depth and resolution with different configurations would be differentially influenced by the conductivity of the seawater. And the construction risk of applying the boat-towed electrode arrays floating on the water and pulled behind a boat with borehole electrode cables and buoyant materials is much lower than a pulled-array on the seafloor. This will achieve a balance among the effect, depth and the efficiency for the ERT in the complex marine environment and finally promote the development and maturity of ERT technology.
Applying the electrical resistivity tomography (ERT) technique in the marine environment claims higher levels in the aspects of instrument, measurement techniques, inversion and interpretation methods and so on. The exploration approaches on issues of geology, natural resources and environment will be further enriched by numerical simulations and actual measurement research of the marine ERT in the coastal area. Based on numerical simulations and field measurements, in this paper it focuses on the research of the resolution and spatial location of the typical geo-electrical models in the offshore area with different arrays such as dipole-dipole, Wenner and Schlumberger. It also studied the effects of seawater conductivity and first conducted two long profile measurements at the site of Pearl River Estuary in the Lingdingyang area. It shows that the detection depth and resolution with different configurations would be differentially influenced by the conductivity of the seawater. And the construction risk of applying the boat-towed electrode arrays floating on the water and pulled behind a boat with borehole electrode cables and buoyant materials is much lower than a pulled-array on the seafloor. This will achieve a balance among the effect, depth and the efficiency for the ERT in the complex marine environment and finally promote the development and maturity of ERT technology.
2020, 45(12): 4563-4573.
doi: 10.3799/dqkx.2020.297
Abstract:
The introduction of artificial intelligence technology into metallogenic prediction can improve the prediction efficiency and research the hidden information between the exploration data and the results. In this paper, it designs a brand new semi-supervised neural network structure based on isolation forest with split-selection criterion(SCiForest) and autoencoder, using the advantage of semi-supervised learning method that the samples are easy to construct and the outstanding application effect in anomaly recognition. Based on the geochemical element data of Gangdise area in Tibet, the copper deposits in the study area is predicted. The prediction results are basically within the known mining area, which shows that the neural network structure in this paper can be used to predict the metallogenic prospective area.
The introduction of artificial intelligence technology into metallogenic prediction can improve the prediction efficiency and research the hidden information between the exploration data and the results. In this paper, it designs a brand new semi-supervised neural network structure based on isolation forest with split-selection criterion(SCiForest) and autoencoder, using the advantage of semi-supervised learning method that the samples are easy to construct and the outstanding application effect in anomaly recognition. Based on the geochemical element data of Gangdise area in Tibet, the copper deposits in the study area is predicted. The prediction results are basically within the known mining area, which shows that the neural network structure in this paper can be used to predict the metallogenic prospective area.
2020, 45(12): 4574-4588.
doi: 10.3799/dqkx.2020.299
Abstract:
In recent years, vector geographic data have been widely used in fields of government, national defense, land, transportation, and marine. Vector geographic data are facing increasingly serious security threats in the process of storage, transmission and sharing. The contradiction between the security protection of vector geographic data and data sharing has become one of the key issues restraining the development of geographic information industry. Considering the above concerns, in this paper it analyzes several key technologies and progresses in existing vector geographic data security protection such as data encryption, data watermarking, data scrambling, and information steganography, and discusses the technical challenges that vector geographic data security protection is facing from the methods and integration of new technologies. Combining with the current advances in the field of vector geographic data and cyberspace security, some important directions for future research and development, such as sensitive information measurement and local dynamic processing, are proposed, which provide some advices for the research and application development of vector geographic data security and data sharing.
In recent years, vector geographic data have been widely used in fields of government, national defense, land, transportation, and marine. Vector geographic data are facing increasingly serious security threats in the process of storage, transmission and sharing. The contradiction between the security protection of vector geographic data and data sharing has become one of the key issues restraining the development of geographic information industry. Considering the above concerns, in this paper it analyzes several key technologies and progresses in existing vector geographic data security protection such as data encryption, data watermarking, data scrambling, and information steganography, and discusses the technical challenges that vector geographic data security protection is facing from the methods and integration of new technologies. Combining with the current advances in the field of vector geographic data and cyberspace security, some important directions for future research and development, such as sensitive information measurement and local dynamic processing, are proposed, which provide some advices for the research and application development of vector geographic data security and data sharing.
2020, 45(12): 4589-4603.
doi: 10.3799/dqkx.2019.260
Abstract:
The Yushishan Nb-Ta mining area is located at the junction of North Altun, Qaidam and Qilian, and the tectonic evolution of this area is complex. The research of petrology, rock geochemistry, zircon U-Pb chronology and zircon Lu-Hf isotope was carried out on the monzonitic granite to reveal petrogenesis and forming environment of it. The detailed name of the monzonitic granite is medium-fine-grained porphyritic biotite monzonitic granite and its dark minerals are mainly biotite and hornblende. The geochemical characteristics show that the monzonitic granite belongs to the typical high-K series with quasi-aluminous to weakly peraluminous. Large ion lithophile elements (Rb, Th and K) are relatively enriched and high field strength elements (Nb, Sr, P and Ti) are in distinct negative anomaly. The REE distribution patterns show negative Eu anomaly, with the mean δEu value of 0.57 and the mean (La/Yb)N value of 11.09, they show that the monzonitic granite magma has a high degree of partial melting. The features of petrological and geochemical indicate that the monzonitic granite belongs to I-type granite. Zircon LA-ICP-MS U-Pb dating of the monzonitic granite yielded a crystallization age of 481.3±1.7 Ma and it was formed in the Early Ordovician. The zircons Lu-Hf isotope analysis shows that the εHf(t) ranges from +0.4 to +11.8 and the two-stage Hf model ages range from 675 to 1 308 Ma, suggesting that the source rocks are partial melting of Neoproterozoic juvenile crustal materials. The formation of the monzonitic granite was closely related to that North Altun oceanic crust subducted Middle-South Qilian continental crust, in the Yushishan area on the edge of Middle-South Qilian continental crust (back arc), the upward intrusion of molten magma from the fractures formed the monzonitic granite because of the subduction of the oceanic crust.
The Yushishan Nb-Ta mining area is located at the junction of North Altun, Qaidam and Qilian, and the tectonic evolution of this area is complex. The research of petrology, rock geochemistry, zircon U-Pb chronology and zircon Lu-Hf isotope was carried out on the monzonitic granite to reveal petrogenesis and forming environment of it. The detailed name of the monzonitic granite is medium-fine-grained porphyritic biotite monzonitic granite and its dark minerals are mainly biotite and hornblende. The geochemical characteristics show that the monzonitic granite belongs to the typical high-K series with quasi-aluminous to weakly peraluminous. Large ion lithophile elements (Rb, Th and K) are relatively enriched and high field strength elements (Nb, Sr, P and Ti) are in distinct negative anomaly. The REE distribution patterns show negative Eu anomaly, with the mean δEu value of 0.57 and the mean (La/Yb)N value of 11.09, they show that the monzonitic granite magma has a high degree of partial melting. The features of petrological and geochemical indicate that the monzonitic granite belongs to I-type granite. Zircon LA-ICP-MS U-Pb dating of the monzonitic granite yielded a crystallization age of 481.3±1.7 Ma and it was formed in the Early Ordovician. The zircons Lu-Hf isotope analysis shows that the εHf(t) ranges from +0.4 to +11.8 and the two-stage Hf model ages range from 675 to 1 308 Ma, suggesting that the source rocks are partial melting of Neoproterozoic juvenile crustal materials. The formation of the monzonitic granite was closely related to that North Altun oceanic crust subducted Middle-South Qilian continental crust, in the Yushishan area on the edge of Middle-South Qilian continental crust (back arc), the upward intrusion of molten magma from the fractures formed the monzonitic granite because of the subduction of the oceanic crust.
2020, 45(12): 4604-4616.
doi: 10.3799/dqkx.2019.290
Abstract:
Mineral inclusions in chromite can record key information of physicochemical conditions (pressure, temperature, etc.), evolution of chemical composition, mechanics of fluid enrichment activities when chromite and its host rock form. However, traditional two-dimensional analytical methods cannot fully reveal the information in tiny and complex inclusions. In this paper, mineral inclusions in the Zunhua podiform chromite from the North China craton were observed and tested by the focused ion beam combined with transmission electron microscopy (FIB-TEM). The mineral types of inclusions are various and mainly include silicate, platinum group mineral, carbonate, and so on. The morphology of these mineral inclusions is also various and complex. Many microstructures and ultra-microstructures are developed in these mineral inclusions such as dislocations, partially open grain/phase boundaries, fluid- or melt-present marks. Therefore, it can be inferred that the Zunhua chromite has complex formation conditions and evolution processes based on the information of mineral types, morphology, and microstructures.
Mineral inclusions in chromite can record key information of physicochemical conditions (pressure, temperature, etc.), evolution of chemical composition, mechanics of fluid enrichment activities when chromite and its host rock form. However, traditional two-dimensional analytical methods cannot fully reveal the information in tiny and complex inclusions. In this paper, mineral inclusions in the Zunhua podiform chromite from the North China craton were observed and tested by the focused ion beam combined with transmission electron microscopy (FIB-TEM). The mineral types of inclusions are various and mainly include silicate, platinum group mineral, carbonate, and so on. The morphology of these mineral inclusions is also various and complex. Many microstructures and ultra-microstructures are developed in these mineral inclusions such as dislocations, partially open grain/phase boundaries, fluid- or melt-present marks. Therefore, it can be inferred that the Zunhua chromite has complex formation conditions and evolution processes based on the information of mineral types, morphology, and microstructures.
2020, 45(12): 4617-4629.
doi: 10.3799/dqkx.2020.072
Abstract:
As a result of the collision between the Tarim plate and the Yili-Central Tianshan plate, the orogenic belt of Southwest Tianshan has experienced secular complex evolution. Metamorphic studies at the southern margin of the Yili-Central Tianshan plate are significant in deciphering the geological history of this orogenic belt. Although metamorphic rocks are widely distributed in this region, study focuses are mainly on the Muzhaerte high-grade rocks. The spatial distribution and tectono-metamorphic evolution of other metamorphic rock types from the same tectonic belt are poorly known. Whether they occur as part of a coherent high-temperature terrane or any other tectonic nappes is fundamental to reconstruct the orogeny of Southwest Tianshan. To resolve this issue, we carry out detailed petrography and temperature estimates using the RSCM (Raman spectroscopy of carbonaceous material, RSCM) thermometry for metamorphic rocks from several sections of the lower part of the Akeyazi valley. Based on textural and structural observations, two types of metamorphic rocks are grouped. Type 1 rocks consist of meta-sedimentary rocks (i.e., meta-siliciclastic and meta-carbonate rocks), with rounded detrital minerals (e.g., quartz and feldspar) and bedding structure locally modified by strong shearing. Type 2 rocks include mica schists and quartzofeldsparthic rocks, uniformly consisting of metamorphic minerals with lepidoblastic to granoblastic texture and well-developed schistosity. The RSCM thermometry suggests that peak temperatures of the former group are 465-597 ℃. They were probably derived from the Carboniferous strata and were locally subjected to mylonitization. Peak temperatures of the latter group are 552-617 ℃, probably as part of the pre-Cambrian basement (the Nalati Group) and they were infiltrated by C-O-H fluids during shearing at shallower levels. This study suggests that the metamorphic rocks of the Lower Akeyazi River have contrasting metamorphic histories and come from different tectonic units, not as an eastern extension of the Muzhaerte high-temperature belt.
As a result of the collision between the Tarim plate and the Yili-Central Tianshan plate, the orogenic belt of Southwest Tianshan has experienced secular complex evolution. Metamorphic studies at the southern margin of the Yili-Central Tianshan plate are significant in deciphering the geological history of this orogenic belt. Although metamorphic rocks are widely distributed in this region, study focuses are mainly on the Muzhaerte high-grade rocks. The spatial distribution and tectono-metamorphic evolution of other metamorphic rock types from the same tectonic belt are poorly known. Whether they occur as part of a coherent high-temperature terrane or any other tectonic nappes is fundamental to reconstruct the orogeny of Southwest Tianshan. To resolve this issue, we carry out detailed petrography and temperature estimates using the RSCM (Raman spectroscopy of carbonaceous material, RSCM) thermometry for metamorphic rocks from several sections of the lower part of the Akeyazi valley. Based on textural and structural observations, two types of metamorphic rocks are grouped. Type 1 rocks consist of meta-sedimentary rocks (i.e., meta-siliciclastic and meta-carbonate rocks), with rounded detrital minerals (e.g., quartz and feldspar) and bedding structure locally modified by strong shearing. Type 2 rocks include mica schists and quartzofeldsparthic rocks, uniformly consisting of metamorphic minerals with lepidoblastic to granoblastic texture and well-developed schistosity. The RSCM thermometry suggests that peak temperatures of the former group are 465-597 ℃. They were probably derived from the Carboniferous strata and were locally subjected to mylonitization. Peak temperatures of the latter group are 552-617 ℃, probably as part of the pre-Cambrian basement (the Nalati Group) and they were infiltrated by C-O-H fluids during shearing at shallower levels. This study suggests that the metamorphic rocks of the Lower Akeyazi River have contrasting metamorphic histories and come from different tectonic units, not as an eastern extension of the Muzhaerte high-temperature belt.
2020, 45(12): 4630-4639.
doi: 10.3799/dqkx.2020.294
Abstract:
The debris flow caused by the outburst of glacial lake is a specific geohazard in the plateau mountainous area. With the study case of Jialong Lake, Nyalam County, Tibet, the hazard assessment model of the debris flow triggered by the outburst of glacial lake was established. Based on the analysis of temperature fluctuation from 1970 to 2015 in the Himalayas area and the historical events of glacial lake outburst in Nyalam County, the temporal probability of the outburst of Jialong Lake in the future 10 years is predicted. The range and magnitude of the unstable ice bodies above Jialong Lake are recognized relying on remote sensing images. The impulse waves generated by glacier landslide are determined with the formula recommended by American Society of Civil Engineers and the modified model of impulse waves in the Three Gorges Reservoir. The pressure of impulse waves and the thrust force of water current acting on the morainal dam are analyzed to assess the failure probability of morainal dam. FlO-2D was used to simulate the movement process of debris flow. The intensity of debris flow triggered by outburst of Jialong Lake were indicated with the maximum velocity and maximum depth of debris flow. The assessment results show that the outburst of Jialong Lake in 2002 was related to the high temperature in that year, and Jialong Lake still has a high probability of outburst in the future; the impulse waves caused by glacial landslide could climb over the top of the morainal dam, which cause rapid erosion and failure of the dam. The debris flow caused by the outburst of Jialong Lake would impact 54 buildings located along the river in Nyalam County. The model proposed in the paper realizes the quantitative hazard assessment of the debris flow caused by glacial lake outburst. The assessment results are of great significance for the risk management of debris flow in Nyalam County.
The debris flow caused by the outburst of glacial lake is a specific geohazard in the plateau mountainous area. With the study case of Jialong Lake, Nyalam County, Tibet, the hazard assessment model of the debris flow triggered by the outburst of glacial lake was established. Based on the analysis of temperature fluctuation from 1970 to 2015 in the Himalayas area and the historical events of glacial lake outburst in Nyalam County, the temporal probability of the outburst of Jialong Lake in the future 10 years is predicted. The range and magnitude of the unstable ice bodies above Jialong Lake are recognized relying on remote sensing images. The impulse waves generated by glacier landslide are determined with the formula recommended by American Society of Civil Engineers and the modified model of impulse waves in the Three Gorges Reservoir. The pressure of impulse waves and the thrust force of water current acting on the morainal dam are analyzed to assess the failure probability of morainal dam. FlO-2D was used to simulate the movement process of debris flow. The intensity of debris flow triggered by outburst of Jialong Lake were indicated with the maximum velocity and maximum depth of debris flow. The assessment results show that the outburst of Jialong Lake in 2002 was related to the high temperature in that year, and Jialong Lake still has a high probability of outburst in the future; the impulse waves caused by glacial landslide could climb over the top of the morainal dam, which cause rapid erosion and failure of the dam. The debris flow caused by the outburst of Jialong Lake would impact 54 buildings located along the river in Nyalam County. The model proposed in the paper realizes the quantitative hazard assessment of the debris flow caused by glacial lake outburst. The assessment results are of great significance for the risk management of debris flow in Nyalam County.
2020, 45(12): 4640-4648.
doi: 10.3799/dqkx.2020.184
Abstract:
To explore the changing law of the consolidation coefficient of saturated soft soil under different consolidation states, based on Terzaghi's consolidation theory, using the relationship between permeability coefficient and void ratio, void ratio, and consolidation stress, the relationship between consolidation coefficient (Cv) and consolidation stress under normal consolidation and over consolidation is derived. The modified Terzaghi one-dimensional consolidation equation considering the influence of stress history and consolidation stress is obtained by substituting the relationship into the Terzaghi equation; The accuracy of the consolidation coefficient relation and the modified Terzaghi one-dimensional consolidation equation were verified by laboratory consolidation test and engineering application analysis. When the consolidation stress is larger, the results show that for normally consolidated soft soil when the consolidation stress is less than the previous consolidation stress, the consolidation coefficient increases with the increase of stress. When the consolidation stress is larger than the previous consolidation stress, the consolidation coefficient decreases with the increase of the stress. For over consolidated soft soil, the coefficient of consolidation increases with the increase of stress and finally tends to be gentle. When the load is small, the calculation results of the Terzaghi one-dimensional consolidation equation before and after the modification are similar; but when the load is large, the consolidation degree of the corrected Terzaghi one-dimensional consolidation equation lags significantly behind the calculation result before the modification. The influence of the previous stress history and the later consolidation stress on the consolidation coefficient of soft soil can not be ignored. The modified Terzaghi one-dimensional consolidation equation can more truly reflect the consolidation behavior of soil.
To explore the changing law of the consolidation coefficient of saturated soft soil under different consolidation states, based on Terzaghi's consolidation theory, using the relationship between permeability coefficient and void ratio, void ratio, and consolidation stress, the relationship between consolidation coefficient (Cv) and consolidation stress under normal consolidation and over consolidation is derived. The modified Terzaghi one-dimensional consolidation equation considering the influence of stress history and consolidation stress is obtained by substituting the relationship into the Terzaghi equation; The accuracy of the consolidation coefficient relation and the modified Terzaghi one-dimensional consolidation equation were verified by laboratory consolidation test and engineering application analysis. When the consolidation stress is larger, the results show that for normally consolidated soft soil when the consolidation stress is less than the previous consolidation stress, the consolidation coefficient increases with the increase of stress. When the consolidation stress is larger than the previous consolidation stress, the consolidation coefficient decreases with the increase of the stress. For over consolidated soft soil, the coefficient of consolidation increases with the increase of stress and finally tends to be gentle. When the load is small, the calculation results of the Terzaghi one-dimensional consolidation equation before and after the modification are similar; but when the load is large, the consolidation degree of the corrected Terzaghi one-dimensional consolidation equation lags significantly behind the calculation result before the modification. The influence of the previous stress history and the later consolidation stress on the consolidation coefficient of soft soil can not be ignored. The modified Terzaghi one-dimensional consolidation equation can more truly reflect the consolidation behavior of soil.
