2014 Vol. 39, No. 7
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2014, 39(7): 775-783.
doi: 10.3799/dqkx.2014.073
Abstract:
It enriches the geological history of Co-rich crusts (CRC) formation and the paleoceanography for us to understand the growth ages and periods of CRC. CRC samples collected from the Magellan and mid-Pacific seamounts were studied for the growth geological ages and periods by employing biostratigraphy (biological impressions). The primary formation geological ages and calcareous nannofossil assembly are different between CM3D06 CRC from the Magellan seamount and CB14 CRC from the mid-Pacific seamount. Based on the identification of calcareous nannofossil imprints and original fossil remains,five growth periods are determined for CM3D06 CRC,namely,Cretaceous (or older),Late Paleocene-Early Eocene,Middle-Late Eocene,Middle-Late Miocene,and Pliocene-Pleistocene,whereas four growth periods for CB14 CRC are determined as follows: Late Paleocene,Middle-Late Eocene,Middle Miocene,and Pliocene to Pleistocene. Regional characteristics for the nannofossil combination features of two CRC samples indicate the impact of oceanic environment on marine organisms and their adaptation. The unconformity of sub-layers and variation of structure and texture of the two CRC samples show that the main hiatus occurred during Oligocene.
It enriches the geological history of Co-rich crusts (CRC) formation and the paleoceanography for us to understand the growth ages and periods of CRC. CRC samples collected from the Magellan and mid-Pacific seamounts were studied for the growth geological ages and periods by employing biostratigraphy (biological impressions). The primary formation geological ages and calcareous nannofossil assembly are different between CM3D06 CRC from the Magellan seamount and CB14 CRC from the mid-Pacific seamount. Based on the identification of calcareous nannofossil imprints and original fossil remains,five growth periods are determined for CM3D06 CRC,namely,Cretaceous (or older),Late Paleocene-Early Eocene,Middle-Late Eocene,Middle-Late Miocene,and Pliocene-Pleistocene,whereas four growth periods for CB14 CRC are determined as follows: Late Paleocene,Middle-Late Eocene,Middle Miocene,and Pliocene to Pleistocene. Regional characteristics for the nannofossil combination features of two CRC samples indicate the impact of oceanic environment on marine organisms and their adaptation. The unconformity of sub-layers and variation of structure and texture of the two CRC samples show that the main hiatus occurred during Oligocene.
2014, 39(7): 784-794.
doi: 10.3799/dqkx.2014.074
Abstract:
Large amount of spores and pollen (mainly consist of pteridophyta spores and gymnospermous pollen), including 54 genera and 90 species, were discovered in the fifth member of Late Permian Linxi Formation, Guandi section, Linxi, Inner Mongolia. The fifth member of Linxi Formation was assumed to belong to the Late Permian, for the preservations of special Late Permian spores and pollen, and biostratigraphic correlations to adjacent areas. 9 genera and 9 species were also found from the sixth member of Linxi Formation. They should belong to the Early Triassic, for the existing characteristics of the Early Triassic palynological assemblages. In addition, the lithology of the sixth member of Linxi Formation varies from that of the underlain parts of Linxi Formation, but similar to that of adjacent Laolongtou Formation, for the yielding of purple-gray silty slate and volcanic breccias interbeds. The sixth member of Linxi Formation might belong to the Early Triassic Laolongtou Formation, evidenced by the integration of lithology, fossils, paleo-climate records and correlations to adjacent areas. The Permian-Triassic boundary is placed in the interval between the fifth member of Linxi Formation and Laolongtou Formation.
Large amount of spores and pollen (mainly consist of pteridophyta spores and gymnospermous pollen), including 54 genera and 90 species, were discovered in the fifth member of Late Permian Linxi Formation, Guandi section, Linxi, Inner Mongolia. The fifth member of Linxi Formation was assumed to belong to the Late Permian, for the preservations of special Late Permian spores and pollen, and biostratigraphic correlations to adjacent areas. 9 genera and 9 species were also found from the sixth member of Linxi Formation. They should belong to the Early Triassic, for the existing characteristics of the Early Triassic palynological assemblages. In addition, the lithology of the sixth member of Linxi Formation varies from that of the underlain parts of Linxi Formation, but similar to that of adjacent Laolongtou Formation, for the yielding of purple-gray silty slate and volcanic breccias interbeds. The sixth member of Linxi Formation might belong to the Early Triassic Laolongtou Formation, evidenced by the integration of lithology, fossils, paleo-climate records and correlations to adjacent areas. The Permian-Triassic boundary is placed in the interval between the fifth member of Linxi Formation and Laolongtou Formation.
2014, 39(7): 795-806.
doi: 10.3799/dqkx.2014.075
Abstract:
The Yangtze Gorges area is one of the hot spots for the investigation of the Neoproterozoic in the world because of its well-preserved stratigraphic sequences recording the "Snowball Earth", "Cap Carbonate", and the "Miaohe Biota". The Qinglinkou section presented in this paper is one of the typical best-outcropped Neoproterozoic sequences in the area, providing good condition for the study of the significant biotic evolution and environmental changes during the critical time. The sequence is in lithostratigraphy composed of the Liantuo, Nantuo, Doushantuo and Dengying formations. The Liantuo Formation includes two sedimentary cycles of purple sandstones intercalated by some thin-bedded shale beds. The Nantuo Formation, uncomfortably overlying on the Liantuo Fm., is characteristic of grayish green diamictites but a member of shale with a few "drop stones" intercalated in the middle part of the formation. The Doushantuo Formation can be well subdivided into four members, among which the first one is "Cap Carbonate", the second dark dolomite interbedded with black shale, the third grey dolomite, and the last member black siliceous shale. The Dengying Formation is featured by the "two white clipping one dark unit" and they correspond with the Hamajing, Shibantan and Baimatuo members respectively. The study of the sedimentary sequence and environmental markers at the Qinglinkou section indicates that the sedimentation in the area started in the Middle Neoproterozoic time and the early sediments were terrestrial facies while the marine facies did not occur until the end of the glaciation of the "Snowball Earth" represented by the Nantuo diamictites. The Ediacaran Doushantuo and Dengying formations are either shallow-sea carbonate or districted shale facies, which became the innovation base for the origin of metazoans and the diversification of macroalgae.
The Yangtze Gorges area is one of the hot spots for the investigation of the Neoproterozoic in the world because of its well-preserved stratigraphic sequences recording the "Snowball Earth", "Cap Carbonate", and the "Miaohe Biota". The Qinglinkou section presented in this paper is one of the typical best-outcropped Neoproterozoic sequences in the area, providing good condition for the study of the significant biotic evolution and environmental changes during the critical time. The sequence is in lithostratigraphy composed of the Liantuo, Nantuo, Doushantuo and Dengying formations. The Liantuo Formation includes two sedimentary cycles of purple sandstones intercalated by some thin-bedded shale beds. The Nantuo Formation, uncomfortably overlying on the Liantuo Fm., is characteristic of grayish green diamictites but a member of shale with a few "drop stones" intercalated in the middle part of the formation. The Doushantuo Formation can be well subdivided into four members, among which the first one is "Cap Carbonate", the second dark dolomite interbedded with black shale, the third grey dolomite, and the last member black siliceous shale. The Dengying Formation is featured by the "two white clipping one dark unit" and they correspond with the Hamajing, Shibantan and Baimatuo members respectively. The study of the sedimentary sequence and environmental markers at the Qinglinkou section indicates that the sedimentation in the area started in the Middle Neoproterozoic time and the early sediments were terrestrial facies while the marine facies did not occur until the end of the glaciation of the "Snowball Earth" represented by the Nantuo diamictites. The Ediacaran Doushantuo and Dengying formations are either shallow-sea carbonate or districted shale facies, which became the innovation base for the origin of metazoans and the diversification of macroalgae.
2014, 39(7): 807-819.
doi: 10.3799/dqkx.2014.076
Abstract:
Researches on the Cenozoic volcanic rocks of the Mangbang Formation in the Mangbang area of the Tengchong block, South China, reveals many granulite xenoliths of felsic granulite and two-pyroxene granulite in trachyandesite. The granulite xenoliths range 3-5 cm in diameters, featured with aligned formation and blastic texture. Equilibrium temperature and pressure estimates for the felsic granulite xenoliths and two-pyroxene granulite xenoliths are 869-969 ℃, 0.94-1.00 GPa and 841-972 ℃ respectively, indicating that they are high temperature granulites. The crystallization temperature and pressure of trachyandesite phenocryst is 1 008-1 059 ℃, 1.26-1.33 GPa, indicating that they were formed in and originated from the lower crust to the top of the upper mantle. Electron backscatter diffraction(EBSD) analyses of two-pyroxene granulite xenoliths show that orthopyroxene and clinopyroxene have obvious lattice preferred orientation (LPO), and the main slip systems are: (010) [001] and (100) [001], (010) [001] respectively. The deformation mechanism is dislocation creep, which indicates that granulite xenoliths experienced a strong plastic deformation and metamorphism. The discovery of high temperature granulite in Cenozoic volcanic rocks suggests that Tengchong Cenozoic magmatic activity may be related with volcanic magamatism and high temperature metamorphism in the lower crustal caused by post-collisional extensional collapse, delamination and slab break-off after subduction and collision of the Indian Plate and the Tengchong block.
Researches on the Cenozoic volcanic rocks of the Mangbang Formation in the Mangbang area of the Tengchong block, South China, reveals many granulite xenoliths of felsic granulite and two-pyroxene granulite in trachyandesite. The granulite xenoliths range 3-5 cm in diameters, featured with aligned formation and blastic texture. Equilibrium temperature and pressure estimates for the felsic granulite xenoliths and two-pyroxene granulite xenoliths are 869-969 ℃, 0.94-1.00 GPa and 841-972 ℃ respectively, indicating that they are high temperature granulites. The crystallization temperature and pressure of trachyandesite phenocryst is 1 008-1 059 ℃, 1.26-1.33 GPa, indicating that they were formed in and originated from the lower crust to the top of the upper mantle. Electron backscatter diffraction(EBSD) analyses of two-pyroxene granulite xenoliths show that orthopyroxene and clinopyroxene have obvious lattice preferred orientation (LPO), and the main slip systems are: (010) [001] and (100) [001], (010) [001] respectively. The deformation mechanism is dislocation creep, which indicates that granulite xenoliths experienced a strong plastic deformation and metamorphism. The discovery of high temperature granulite in Cenozoic volcanic rocks suggests that Tengchong Cenozoic magmatic activity may be related with volcanic magamatism and high temperature metamorphism in the lower crustal caused by post-collisional extensional collapse, delamination and slab break-off after subduction and collision of the Indian Plate and the Tengchong block.
2014, 39(7): 820-836.
doi: 10.3799/dqkx.2014.077
Abstract:
The Chalukou Mo deposit lies in the northern Great Xing'an Range, in which veinlet and breccia dominate mineralization. The whole hydrothermal ore-forming processes involve the following four stages: I. quartz-potash feldspar stage; II. quartz-molybdenite stage; III. quartz-polymetallic sulfide stage; IV. quartz-fluorite-calcite stage. The petrographic and laser Raman spectroscopy study show that the melt-fluid inclusions in quartz phenocryst contain component of oligoclase and albite, indicating they directly exsolved from primary magma. Halite, sylvite, hematite, and gypsum are recognized as daughter minerals in S-type inclusions of granite porphyry, suggesting high oxygen fugacity. The stageⅠquartz captures (L+V)-type, C-type, and S-type (contain halite, sylvite, hematite, and anhydrite daughter minerals) fluid inclusions. The stage Ⅱ quartz captures (L+V)-type, C-type, and S-type (contain halite, sylvite, chalcopyrite, and molybdenite daughter minerals) fluid inclusions, in addition, V-type and S-type fluid inclusions are coexistent. In the stage III, there are (L+V)-type and S-type with calcite as daughter minerals. Stage IV develops (L+V)-type and L-type fluid inclusions. Microthermometric data show the homogenization temperatures (530 ℃→120 ℃) and salinities (66.7% NaCl equiv→1.2% NaCl equiv) decrease gradually. The gas components have a certain amount of CO2 in every stage, and the liquid components in fluid inclusions have Na+, K+, Ca2+, Cl-, and SO42-, and small amount of F-. The initial fluids are high oxygen fugacity and salinity NaCl-H2O-CO2 fluid system with abundant CO2. The homogenization temperatures, salinities, lgfO2, and CO2 content tend to fall from the early to late stage. The decline of homogenization temperatures, salinities, and CO2 content as well as sericitization greatly hinder the depositing of metallogenic elements.
The Chalukou Mo deposit lies in the northern Great Xing'an Range, in which veinlet and breccia dominate mineralization. The whole hydrothermal ore-forming processes involve the following four stages: I. quartz-potash feldspar stage; II. quartz-molybdenite stage; III. quartz-polymetallic sulfide stage; IV. quartz-fluorite-calcite stage. The petrographic and laser Raman spectroscopy study show that the melt-fluid inclusions in quartz phenocryst contain component of oligoclase and albite, indicating they directly exsolved from primary magma. Halite, sylvite, hematite, and gypsum are recognized as daughter minerals in S-type inclusions of granite porphyry, suggesting high oxygen fugacity. The stageⅠquartz captures (L+V)-type, C-type, and S-type (contain halite, sylvite, hematite, and anhydrite daughter minerals) fluid inclusions. The stage Ⅱ quartz captures (L+V)-type, C-type, and S-type (contain halite, sylvite, chalcopyrite, and molybdenite daughter minerals) fluid inclusions, in addition, V-type and S-type fluid inclusions are coexistent. In the stage III, there are (L+V)-type and S-type with calcite as daughter minerals. Stage IV develops (L+V)-type and L-type fluid inclusions. Microthermometric data show the homogenization temperatures (530 ℃→120 ℃) and salinities (66.7% NaCl equiv→1.2% NaCl equiv) decrease gradually. The gas components have a certain amount of CO2 in every stage, and the liquid components in fluid inclusions have Na+, K+, Ca2+, Cl-, and SO42-, and small amount of F-. The initial fluids are high oxygen fugacity and salinity NaCl-H2O-CO2 fluid system with abundant CO2. The homogenization temperatures, salinities, lgfO2, and CO2 content tend to fall from the early to late stage. The decline of homogenization temperatures, salinities, and CO2 content as well as sericitization greatly hinder the depositing of metallogenic elements.
2014, 39(7): 837-847.
doi: 10.3799/dqkx.2014.078
Abstract:
This paper re-constructs and analyzes dynamic process of hydrocarbon accumulation in the central part of Xihu depression by using the geological data, geophysical and geochemical techniques of basin modeling in accordance with geological comparison principles. It is found that the depositional filling and tectonic subsidence experienced episodic evolution in study area with its sedimentation thickness and subsidence rate reaching the biggest value in Eocene. The organic matter evolution of source rock is characterized by short maturation, narrow zone of oil generation and broad zone of gas generation. The main source rock of Pinghu Formation reached oil threshold earlier with strong hydrocarbon generation-expulsion capacity, and the generation-expulsion process occurred in early Late Oligocene and Early-Miocene to Mid-Miocene. The petroleum migration and accumulation are controlled by the paleo-structure surface, and the confluence flowing mainly occurs in the Baochu gentle slope zone and Tianping fault steep slope zone while the planar flowing occurs in the central anticline belt. There are several favorable zones of petroleum accumulation in the study area, and the major accumulation of oil and gas occurred over the Longjing movement (7 Ma).
This paper re-constructs and analyzes dynamic process of hydrocarbon accumulation in the central part of Xihu depression by using the geological data, geophysical and geochemical techniques of basin modeling in accordance with geological comparison principles. It is found that the depositional filling and tectonic subsidence experienced episodic evolution in study area with its sedimentation thickness and subsidence rate reaching the biggest value in Eocene. The organic matter evolution of source rock is characterized by short maturation, narrow zone of oil generation and broad zone of gas generation. The main source rock of Pinghu Formation reached oil threshold earlier with strong hydrocarbon generation-expulsion capacity, and the generation-expulsion process occurred in early Late Oligocene and Early-Miocene to Mid-Miocene. The petroleum migration and accumulation are controlled by the paleo-structure surface, and the confluence flowing mainly occurs in the Baochu gentle slope zone and Tianping fault steep slope zone while the planar flowing occurs in the central anticline belt. There are several favorable zones of petroleum accumulation in the study area, and the major accumulation of oil and gas occurred over the Longjing movement (7 Ma).
2014, 39(7): 848-857.
doi: 10.3799/dqkx.2014.079
Abstract:
This paper discusses the key control factors of shale oil enrichment and producibility. It is found that whether shale oil can effectively accumulate and has producibility is mainly controlled by six factors, namely, hydrocarbon generation amount, porosity, preservation condition, reservoir reconstruction condition, crude oil property and development scheme. A break-through of shale oil development has been made in Anshen-1 Well and Biye-1 Well due to their advantages for shale oil enrichment and producibility, including high organic matter abundance, excellent organic matter type and high brittle mineral content, good development of lamellation, structural fracture. But there are also disadvantages. Firstly, maturity of organic matter is low, which influences oil content of shale and physical property of crude oil. Secondly, there is no overpressure in Biyang depression, indicating the preservation condition of shale oil is not good and the stratum energy is low. So the southeast area where the shale has higher depth can be the favorable area for shale oil exploration and exploitation. It is concluded that the decrease of reservoir pressure shall be delayed during production due to the influence of dissolved gas amount on physical property of crude oil and the stress sensitivity of low permeability reservoir.
This paper discusses the key control factors of shale oil enrichment and producibility. It is found that whether shale oil can effectively accumulate and has producibility is mainly controlled by six factors, namely, hydrocarbon generation amount, porosity, preservation condition, reservoir reconstruction condition, crude oil property and development scheme. A break-through of shale oil development has been made in Anshen-1 Well and Biye-1 Well due to their advantages for shale oil enrichment and producibility, including high organic matter abundance, excellent organic matter type and high brittle mineral content, good development of lamellation, structural fracture. But there are also disadvantages. Firstly, maturity of organic matter is low, which influences oil content of shale and physical property of crude oil. Secondly, there is no overpressure in Biyang depression, indicating the preservation condition of shale oil is not good and the stratum energy is low. So the southeast area where the shale has higher depth can be the favorable area for shale oil exploration and exploitation. It is concluded that the decrease of reservoir pressure shall be delayed during production due to the influence of dissolved gas amount on physical property of crude oil and the stress sensitivity of low permeability reservoir.
2014, 39(7): 858-870.
doi: 10.3799/dqkx.2014.080
Abstract:
Ancient shelf sand ridge deposited in Lower member of Silurian Kepingtage Formation of Shuntuoguole uplift, Tarim basin, provides an ideal example to understand its sedimentary formation characteristics. By using well-logging and core data, shelf sand ridge is divided into 6 lithofacies: massive bedding medium-fine sandstone (FA1), hummocky cross bedding medium-fine sandstone (FA2), muddy conglomerate-bearing medium-fine sandstone (FA3), clay layer-bearing bimodal cross bedding fine sandstone (FA4), tidal bedding fine sandstone interbedded with mudstone (FA5), horizontal bedding shelf mudstone (FA6) according to the lithology and sedimentary structure of sediments. In terms of lithofacies association characteristics, shelf sand ridge whose deposits are affected by shelf tide and storm wave is classified into 4 sedimentary microfacies: sand ridge core microfacies (FA1-FA2-FA3), sand ridge inner margin microfacies (FA4), sand ridge external margin (FA5) and shelf mud microfacies (FA6). The plane distribution characteristics of shelf sand ridge along NE-SW and NW-SE are determined through detailed analysis of three-dimensional seismic slice attributes calibrated with well data. Ancient shelf sand ridge reservoir has characteristics of extra low porosity and permeability, in which sand ridge core microfacies is better reservoir with average porosity 6.96%, average permeability 0.34×10-3 μm2, and is mainly industrial oil flow concentrated area. Syndepositional slightly anticline-lithologic traps are often formed since sandstones of shelf sand ridge present ridge or mound shape and draped by thick-layer shelf mudstone.
Ancient shelf sand ridge deposited in Lower member of Silurian Kepingtage Formation of Shuntuoguole uplift, Tarim basin, provides an ideal example to understand its sedimentary formation characteristics. By using well-logging and core data, shelf sand ridge is divided into 6 lithofacies: massive bedding medium-fine sandstone (FA1), hummocky cross bedding medium-fine sandstone (FA2), muddy conglomerate-bearing medium-fine sandstone (FA3), clay layer-bearing bimodal cross bedding fine sandstone (FA4), tidal bedding fine sandstone interbedded with mudstone (FA5), horizontal bedding shelf mudstone (FA6) according to the lithology and sedimentary structure of sediments. In terms of lithofacies association characteristics, shelf sand ridge whose deposits are affected by shelf tide and storm wave is classified into 4 sedimentary microfacies: sand ridge core microfacies (FA1-FA2-FA3), sand ridge inner margin microfacies (FA4), sand ridge external margin (FA5) and shelf mud microfacies (FA6). The plane distribution characteristics of shelf sand ridge along NE-SW and NW-SE are determined through detailed analysis of three-dimensional seismic slice attributes calibrated with well data. Ancient shelf sand ridge reservoir has characteristics of extra low porosity and permeability, in which sand ridge core microfacies is better reservoir with average porosity 6.96%, average permeability 0.34×10-3 μm2, and is mainly industrial oil flow concentrated area. Syndepositional slightly anticline-lithologic traps are often formed since sandstones of shelf sand ridge present ridge or mound shape and draped by thick-layer shelf mudstone.
2014, 39(7): 871-879.
doi: 10.3799/dqkx.2014.081
Abstract:
The development of dolomite reservoirs is mainly influenced by primary sedimentary lithology and later dissolution action, whereas the primary sedimentary lithology is controlled by pre-depositional paleogeomorphology and the dissolution action is controlled by karst-geomorphology. In M Block, the favorable reservoir rock of KT-Ⅰ is dissolution dolomite and is distributed in the upper formation, with its pore types mainly including intercrystalline pores, intercrystalline solution pores, intergranular solution pores and organic visceral pores. The paleogeomorphology in Carboniferous in M Block is featured with "higher in west and lower in east" and "lower in west and higher in east" in Early Permian, with the eroded top formation of KT-Ⅰ. This study applies residual thickness method and mould method for recovery of the pre-depositional paleogeomorphology and the karst-geomorphology respectively, and suggests the favorable area of dolomite reservoirs occurs in the overlap zone of the pre-depositional paleogeomorphology highland and karst-slope zone, and it is further suggested that exploration area for potential dolomite reservoirs is to be extended southward and eastward. Three appraisal wells in central-southern and southern areas yield good results. The study shows the paleogeomorphology recovery technique is effective for predicting dolomite reservoir in M Block.
The development of dolomite reservoirs is mainly influenced by primary sedimentary lithology and later dissolution action, whereas the primary sedimentary lithology is controlled by pre-depositional paleogeomorphology and the dissolution action is controlled by karst-geomorphology. In M Block, the favorable reservoir rock of KT-Ⅰ is dissolution dolomite and is distributed in the upper formation, with its pore types mainly including intercrystalline pores, intercrystalline solution pores, intergranular solution pores and organic visceral pores. The paleogeomorphology in Carboniferous in M Block is featured with "higher in west and lower in east" and "lower in west and higher in east" in Early Permian, with the eroded top formation of KT-Ⅰ. This study applies residual thickness method and mould method for recovery of the pre-depositional paleogeomorphology and the karst-geomorphology respectively, and suggests the favorable area of dolomite reservoirs occurs in the overlap zone of the pre-depositional paleogeomorphology highland and karst-slope zone, and it is further suggested that exploration area for potential dolomite reservoirs is to be extended southward and eastward. Three appraisal wells in central-southern and southern areas yield good results. The study shows the paleogeomorphology recovery technique is effective for predicting dolomite reservoir in M Block.
2014, 39(7): 880-888.
doi: 10.3799/dqkx.2014.082
Abstract:
A new effective recovery method of crude Se by Na2SO3 is presented from high efficient calcium-adsorbent used for combustion of Se-rich stone coal, which was collected from Yutangba, Enshi, Hubei Province. The reduction of Se reaches 98.48±1.95% (n=3) in the simulation process and the optimium parameters are determined as follows: terperature 353 K, time 15 mins, HCl concentration 4 mol·L-1 and mass ratio between Na2SO3 to Se of 6∶1. An acceptable recovery rate of selenium was also obtained from the actual experiment using Se-rich stone coal. The XRD and SEM-EDS analysis results show that the crystal system and purity of Se are controlled by many factors in the reaction system.
A new effective recovery method of crude Se by Na2SO3 is presented from high efficient calcium-adsorbent used for combustion of Se-rich stone coal, which was collected from Yutangba, Enshi, Hubei Province. The reduction of Se reaches 98.48±1.95% (n=3) in the simulation process and the optimium parameters are determined as follows: terperature 353 K, time 15 mins, HCl concentration 4 mol·L-1 and mass ratio between Na2SO3 to Se of 6∶1. An acceptable recovery rate of selenium was also obtained from the actual experiment using Se-rich stone coal. The XRD and SEM-EDS analysis results show that the crystal system and purity of Se are controlled by many factors in the reaction system.
2014, 39(7): 889-895.
doi: 10.3799/dqkx.2014.083
Abstract:
A region of 1 000 km2 in Enshi, Hubei Province is chosen as the typical study area, and its historical landslide data are comprehensively analyzed in this paper. The strata in the study area are divided into three types including high, middle and low susceptible petrofabrics according to the relationship between local landslide formation and lithology. The scatter diagrams about effective rainfall intensity and critical duration are obtained based on rainfall monitoring data and historical information of landslides in each petrofabric. Thus effective rainfall intensity thresholds are determined and landslide hazard warning model of the study area is suggested. In this study, landslide prediction evaluating system is firstly established based on data of sample area, and then landslide susceptibility distribution map is obtained by using GIS. According to Different Susceptible Petrofabric-Effective Rainfall Intensity Models, the landslide hazard warning is realized by overlaying landslide susceptibility distribution map and rainfall risk grade distribution results. Results show that the hazard warning results fit well with the actual situation. Thus, the warning model is verified to be effective, accurate and comprehensive to provide scientific evidence for preventing and reducing disasters.
A region of 1 000 km2 in Enshi, Hubei Province is chosen as the typical study area, and its historical landslide data are comprehensively analyzed in this paper. The strata in the study area are divided into three types including high, middle and low susceptible petrofabrics according to the relationship between local landslide formation and lithology. The scatter diagrams about effective rainfall intensity and critical duration are obtained based on rainfall monitoring data and historical information of landslides in each petrofabric. Thus effective rainfall intensity thresholds are determined and landslide hazard warning model of the study area is suggested. In this study, landslide prediction evaluating system is firstly established based on data of sample area, and then landslide susceptibility distribution map is obtained by using GIS. According to Different Susceptible Petrofabric-Effective Rainfall Intensity Models, the landslide hazard warning is realized by overlaying landslide susceptibility distribution map and rainfall risk grade distribution results. Results show that the hazard warning results fit well with the actual situation. Thus, the warning model is verified to be effective, accurate and comprehensive to provide scientific evidence for preventing and reducing disasters.
2014, 39(7): 896-904.
doi: 10.3799/dqkx.2014.084
Abstract:
It is worthy of attention yet has been neglected for long time to explore effects of geo-stress on carbonate dissolution and karst evolution. A comprehensive analysis about the effects of geo-stress is carried out based on theories of geochemistry, mineralogy, petrology, geo-thermodynamics, and plastoelasticity in this study. The results reveal that the involvement of stress can change the dissolution rate of carbonate rocks by raising the strain energy and free energy of dissolution and changing the fracture characteristics and groundwater movement in carbonate rock, which leads to an increase of saturated concentration dissolved carbonate matters on the water-rock interface and changes of the depth and flow pattern of water and concentration of dissolved carbonate matters in water in carbonate rock fractures, and which can change the active area of interaction between carbonate rock and water in turn. Moreover, there exists a coupling and competitive mechanism because of stress-dissolution in carbonic rocks, which leads to behaviors of chaos and self-organization in the karst evolution. And so the effect of stress should not be ignored due to the fact that a minor change in the beginning aroused by stress can lead to great change in the evolution progress of karst, and the natural phenomenon of coexistence between dissolution and precipitation, moniliform distributed karst caves and isolated karst caves may be the results of the self-organization because of coupling and competitive behaviors aroused by stress-dissolution.
It is worthy of attention yet has been neglected for long time to explore effects of geo-stress on carbonate dissolution and karst evolution. A comprehensive analysis about the effects of geo-stress is carried out based on theories of geochemistry, mineralogy, petrology, geo-thermodynamics, and plastoelasticity in this study. The results reveal that the involvement of stress can change the dissolution rate of carbonate rocks by raising the strain energy and free energy of dissolution and changing the fracture characteristics and groundwater movement in carbonate rock, which leads to an increase of saturated concentration dissolved carbonate matters on the water-rock interface and changes of the depth and flow pattern of water and concentration of dissolved carbonate matters in water in carbonate rock fractures, and which can change the active area of interaction between carbonate rock and water in turn. Moreover, there exists a coupling and competitive mechanism because of stress-dissolution in carbonic rocks, which leads to behaviors of chaos and self-organization in the karst evolution. And so the effect of stress should not be ignored due to the fact that a minor change in the beginning aroused by stress can lead to great change in the evolution progress of karst, and the natural phenomenon of coexistence between dissolution and precipitation, moniliform distributed karst caves and isolated karst caves may be the results of the self-organization because of coupling and competitive behaviors aroused by stress-dissolution.
2014, 39(7): 905-914.
doi: 10.3799/dqkx.2014.085
Abstract:
Based on glacial isostatic adjustment (GIA) models of different mantle viscosities, the contribution from different layers in the earth's interior to the GIA viscous gravity perturbation rates is investigated, and the approximate relation between GIA gravity perturbation rate and uplift rate and whether it is independent of the mantle viscosity are validated in this paper. Furthermore, the Wahr's approximate relation with the data from absolute gravimetry and global positioning system (GPS) was checked. It is found that the contribution of the lithosphere to GIA gravity perturbation rate and geoid anomaly rate is more than 86%, the contribution of the five layers under the lithosphere to GIA gravity signal is less than 14% yet. The relative difference between GIA uplift rate calculated by using approximate relation and that by the finite element method is about 15%, and the difference does not depend on changes in the mantle viscosity. The ratio of gravity versus uplift obtained by ground-based measurements in North America is 0.141±0.014 μGal/mm, which is very close to 0.154 μGal/mm of Wahr's theoretical ratio. The relative difference between the two ratio values above is just 9.2%. Therefore, this study gives the uncertainty value of the Wahr's approximate relation between 9.2%-15.0%, which can be used to evaluate the effects on the results of the separated GIA and present-day mass balance signals.
Based on glacial isostatic adjustment (GIA) models of different mantle viscosities, the contribution from different layers in the earth's interior to the GIA viscous gravity perturbation rates is investigated, and the approximate relation between GIA gravity perturbation rate and uplift rate and whether it is independent of the mantle viscosity are validated in this paper. Furthermore, the Wahr's approximate relation with the data from absolute gravimetry and global positioning system (GPS) was checked. It is found that the contribution of the lithosphere to GIA gravity perturbation rate and geoid anomaly rate is more than 86%, the contribution of the five layers under the lithosphere to GIA gravity signal is less than 14% yet. The relative difference between GIA uplift rate calculated by using approximate relation and that by the finite element method is about 15%, and the difference does not depend on changes in the mantle viscosity. The ratio of gravity versus uplift obtained by ground-based measurements in North America is 0.141±0.014 μGal/mm, which is very close to 0.154 μGal/mm of Wahr's theoretical ratio. The relative difference between the two ratio values above is just 9.2%. Therefore, this study gives the uncertainty value of the Wahr's approximate relation between 9.2%-15.0%, which can be used to evaluate the effects on the results of the separated GIA and present-day mass balance signals.
