2006 Vol. 31, No. 3
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2006, 31(3): 285-293.
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Abstract:
The early tectonic evolution of craton has been the target topic for continental geology. Based on a preliminary analysis on the tectonic map (1∶2000000) of North China craton (NCC) basement, we try to investigate its tectonic boundaries, structural pattern, and late stage reworking. Guided by the framework of modern plate tectonics, the NCC basement is divided into different tectonic units. It is suggested here that some key geological units (KGU), with distinct tectonic setting and geological origin, may well preserve information of its early tectonic history. With the high-precision isotopic age dating of KGU, a new timetable of geological and geochrological events has been defined for the Early Precambrian geology of NCC. In addition, several major tectonothermal episodes can be revealed by the synthesis of available age data with TTG-granite gneiss and mafic volcanics. Therefore, the Early Precambrian tectonic evolution of NCC is documented by a consideration of both regional geological research and age dating.As indicated by widespread geological research and high-precision geochronology, NCC's basement was mainly consisted of Neoarchean TTG complex and supracrustal sequences, associated with rapid crustal accretion within the setting of active continental margins and collisions between different blocks. As a result, it became stabilized at the end of the Archean. In the Early Paleoproterozoic, the NCC began to be dominated by an extensional tectonic regime, characterized by the development of early cover. In the Late Paleoproterozoic, the NCC collided with another block in the north, with formation of a supercraton, which caused a strong tectonothermal reworking to its passive margin in the northwestern part of NCC. At about 1.84 Ga, the NCC underwent extension, recorded its dispersal from a supercraton. After that, it began its tectonic evolution independently, its basement was intensely uplifted and eroded, with development of sedimentary cover. The Early Precambrian tectonic framework and geological events documented will provide an important constraint for reconstruction of the NCC within the early supercontinents.
The early tectonic evolution of craton has been the target topic for continental geology. Based on a preliminary analysis on the tectonic map (1∶2000000) of North China craton (NCC) basement, we try to investigate its tectonic boundaries, structural pattern, and late stage reworking. Guided by the framework of modern plate tectonics, the NCC basement is divided into different tectonic units. It is suggested here that some key geological units (KGU), with distinct tectonic setting and geological origin, may well preserve information of its early tectonic history. With the high-precision isotopic age dating of KGU, a new timetable of geological and geochrological events has been defined for the Early Precambrian geology of NCC. In addition, several major tectonothermal episodes can be revealed by the synthesis of available age data with TTG-granite gneiss and mafic volcanics. Therefore, the Early Precambrian tectonic evolution of NCC is documented by a consideration of both regional geological research and age dating.As indicated by widespread geological research and high-precision geochronology, NCC's basement was mainly consisted of Neoarchean TTG complex and supracrustal sequences, associated with rapid crustal accretion within the setting of active continental margins and collisions between different blocks. As a result, it became stabilized at the end of the Archean. In the Early Paleoproterozoic, the NCC began to be dominated by an extensional tectonic regime, characterized by the development of early cover. In the Late Paleoproterozoic, the NCC collided with another block in the north, with formation of a supercraton, which caused a strong tectonothermal reworking to its passive margin in the northwestern part of NCC. At about 1.84 Ga, the NCC underwent extension, recorded its dispersal from a supercraton. After that, it began its tectonic evolution independently, its basement was intensely uplifted and eroded, with development of sedimentary cover. The Early Precambrian tectonic framework and geological events documented will provide an important constraint for reconstruction of the NCC within the early supercontinents.
2006, 31(3): 294-300.
Abstract:
LA-ICPMS U-Pb dating was conducted on three textural domains in zircon from a high-temperature high-pressure felsic granulite in the Huangtuling area, North Dabieshan, Central China. The metamorphic growth-derived detrital zircon domain yielded a 207Pb/206Pb age in the range of (2 493±54) - (2 500±180) Ma. The magmatic genesis-derived detrital zircon domain gave a 207Pb/206Pb age ranging from 2 628 Ma to 2 690 Ma, with an oldest 206Pb/238U age of (2 790±150) Ma. The metamorphic overgrowth or metamorphic recrystallization zircon domain yielded a discordia with an upper intercept age of (2 044.7±29.3) Ma. Compositions of the mineral assemblage, major element geochemistry, and an especially complex interior texture of zircon suggest that the protolith of the felsic granulite is of sedimentary origin. The protolith material of the granulite came from a provenance with a complex thermal history, i.e. 2.8 Ga magmatism and 2.5 Ga metamorphism, and deposited in a basin not earlier than 2.5 Ga. The high-temperature and high-pressure granulite-facies metamorphic age was precisely constrained at (2.04±0.03) Ga, which indicates the granulite in Huangtuling area should be a relict of the Paleoproterozoic UHT metamorphosed slab.
LA-ICPMS U-Pb dating was conducted on three textural domains in zircon from a high-temperature high-pressure felsic granulite in the Huangtuling area, North Dabieshan, Central China. The metamorphic growth-derived detrital zircon domain yielded a 207Pb/206Pb age in the range of (2 493±54) - (2 500±180) Ma. The magmatic genesis-derived detrital zircon domain gave a 207Pb/206Pb age ranging from 2 628 Ma to 2 690 Ma, with an oldest 206Pb/238U age of (2 790±150) Ma. The metamorphic overgrowth or metamorphic recrystallization zircon domain yielded a discordia with an upper intercept age of (2 044.7±29.3) Ma. Compositions of the mineral assemblage, major element geochemistry, and an especially complex interior texture of zircon suggest that the protolith of the felsic granulite is of sedimentary origin. The protolith material of the granulite came from a provenance with a complex thermal history, i.e. 2.8 Ga magmatism and 2.5 Ga metamorphism, and deposited in a basin not earlier than 2.5 Ga. The high-temperature and high-pressure granulite-facies metamorphic age was precisely constrained at (2.04±0.03) Ga, which indicates the granulite in Huangtuling area should be a relict of the Paleoproterozoic UHT metamorphosed slab.
2006, 31(3): 301-308.
Abstract:
We attempt to recover the paleoenvironments recorded in the accretion of a typical new-type hydrogenetic ferromanganese crust from the deep water areas of the East Philippine Sea. From detailed geochemical and U-series chronological studies, three major accretion periods and corresponding paleoenvironments can be ascertained. The first period is a faster accretion period in the terminal Late Miocene to the Early Pliocene with looser structure and higher volcanic detritus contents, corresponding to the active Antarctic bottom waters and depressed temperature from the intermediate Middle Miocene to the Early Pliocene. The second period is a pulse of pelagic clay deposition at the Early to Middle Pliocene, reflecting the shrinkage of the Antarctic bottom waters and the global temperature elevation of this period. The third period is a slower accretion period from the Middle Pliocene, which indicates the more violent activity of Antarctic bottom waters once again and more depressed temperature than the first period, facilitating the accretion of a more compact and pure ferromanganese zone. The paleoceanographic histories of these studied areas had not been made clear in previous research.
We attempt to recover the paleoenvironments recorded in the accretion of a typical new-type hydrogenetic ferromanganese crust from the deep water areas of the East Philippine Sea. From detailed geochemical and U-series chronological studies, three major accretion periods and corresponding paleoenvironments can be ascertained. The first period is a faster accretion period in the terminal Late Miocene to the Early Pliocene with looser structure and higher volcanic detritus contents, corresponding to the active Antarctic bottom waters and depressed temperature from the intermediate Middle Miocene to the Early Pliocene. The second period is a pulse of pelagic clay deposition at the Early to Middle Pliocene, reflecting the shrinkage of the Antarctic bottom waters and the global temperature elevation of this period. The third period is a slower accretion period from the Middle Pliocene, which indicates the more violent activity of Antarctic bottom waters once again and more depressed temperature than the first period, facilitating the accretion of a more compact and pure ferromanganese zone. The paleoceanographic histories of these studied areas had not been made clear in previous research.
2006, 31(3): 309-316.
Abstract:
In order to understand the time-space changes of the Cenozoic tectonic paleostress in the Kuqa depression, detailed field observations and measurements were carried out. Paleostress evolution history is discussed from the Late Cretaceous, according to the relationship between brittle structures and stresses. Their sequence relation is inferred from field investigations and the calculated results indicate that the early ENE-WSW systematic joints caused by regional uplifting were cut and reworked by late NNW-SSE and NW-SE systematic joints. This corresponds to the change of regional stresses from weak extension to strong compression since the beginning of the Neogene.Resultsof paleostress inversion based on large amounts of fault-slip data display a stress pattern with near N-S extension on the basin margin and NW-SE compression in the basin interior. So at the beginning of the Neogene, the stress field changed and the maximal principal stress σ1 switched from vertical to horizontal. The rapid vertical uplifting of the Tianshan Mountains might be responsible for the stress difference between the basin range and interior.
In order to understand the time-space changes of the Cenozoic tectonic paleostress in the Kuqa depression, detailed field observations and measurements were carried out. Paleostress evolution history is discussed from the Late Cretaceous, according to the relationship between brittle structures and stresses. Their sequence relation is inferred from field investigations and the calculated results indicate that the early ENE-WSW systematic joints caused by regional uplifting were cut and reworked by late NNW-SSE and NW-SE systematic joints. This corresponds to the change of regional stresses from weak extension to strong compression since the beginning of the Neogene.Resultsof paleostress inversion based on large amounts of fault-slip data display a stress pattern with near N-S extension on the basin margin and NW-SE compression in the basin interior. So at the beginning of the Neogene, the stress field changed and the maximal principal stress σ1 switched from vertical to horizontal. The rapid vertical uplifting of the Tianshan Mountains might be responsible for the stress difference between the basin range and interior.
2006, 31(3): 317-320.
Abstract:
Although there has been intensive research on improving the discharge voltage plateau of lithium manganese oxide doped by transition metals, there is a lack of corresponding studies on the improvement mechanism. In this paper, we investigate the electronic structure of spinel manganese oxide doping with transition metal M (M=Ti, Cr, Fe, Co, Ni, Cu, Zn) by first principles calculation based on the density functional theory. The calculated density of states indicates that a new O-2p band induced by the M-3d band appears at the exact position of the M-3d band itself. The compensating electrons are removed from the O-2p levels neighboring the Fermi level when the Li ion is removed. The position of the M-3d band shifts gradually to the low energy direction as M varies from Ti to Zn in the transition metal row of the periodic table, and the position of the new O-2p band also shifts downward following the M-3d band. The withdrawal of lithium electrons from this low O-2p band will result in high cell voltage.
Although there has been intensive research on improving the discharge voltage plateau of lithium manganese oxide doped by transition metals, there is a lack of corresponding studies on the improvement mechanism. In this paper, we investigate the electronic structure of spinel manganese oxide doping with transition metal M (M=Ti, Cr, Fe, Co, Ni, Cu, Zn) by first principles calculation based on the density functional theory. The calculated density of states indicates that a new O-2p band induced by the M-3d band appears at the exact position of the M-3d band itself. The compensating electrons are removed from the O-2p levels neighboring the Fermi level when the Li ion is removed. The position of the M-3d band shifts gradually to the low energy direction as M varies from Ti to Zn in the transition metal row of the periodic table, and the position of the new O-2p band also shifts downward following the M-3d band. The withdrawal of lithium electrons from this low O-2p band will result in high cell voltage.
2006, 31(3): 321-325.
Abstract:
In recent years, geological evidence and the available experimental data have shown that a significant quantity of copper can be transported in vapor. It has been recognized that the transport of copper in vapor may be an important geochemical process. But, up to now, little work has been done on the mechanisms of dissolution of copper in vapor. In this paper, the solubility of copper in undersaturated water vapor was investigated experimentally at temperatures of 310 to 350℃and pressures from 4. 2 to 10 MPa. Results of these experiments show that the presence of water vapor increases the concentration of Cu in the gas. At the same temperature, the solubility of copper increases with the increase of water vapor pressure. Copper may exist as hydrated gaseous particles in the vapor phase. The dissolution process can be described by the reaction: CuClmsolid +nH2O gas=CuClm·(H2O)ngas(m=1, 2). The hydration number decreases with increasing temperature, varying from -6 at 310 ℃, to -5 at 330 ℃ and -4 at 350℃. The results show that the interactions between gas-solvent H2O and copper significantly enhance the capacity of dissolution and transport of copper in the gas phase.
In recent years, geological evidence and the available experimental data have shown that a significant quantity of copper can be transported in vapor. It has been recognized that the transport of copper in vapor may be an important geochemical process. But, up to now, little work has been done on the mechanisms of dissolution of copper in vapor. In this paper, the solubility of copper in undersaturated water vapor was investigated experimentally at temperatures of 310 to 350℃and pressures from 4. 2 to 10 MPa. Results of these experiments show that the presence of water vapor increases the concentration of Cu in the gas. At the same temperature, the solubility of copper increases with the increase of water vapor pressure. Copper may exist as hydrated gaseous particles in the vapor phase. The dissolution process can be described by the reaction: CuClmsolid +nH2O gas=CuClm·(H2O)ngas(m=1, 2). The hydration number decreases with increasing temperature, varying from -6 at 310 ℃, to -5 at 330 ℃ and -4 at 350℃. The results show that the interactions between gas-solvent H2O and copper significantly enhance the capacity of dissolution and transport of copper in the gas phase.
2006, 31(3): 326-329.
Abstract:
To meet the requirements of Earth System Science (ESS) development in China, a state-of-the-art study has been carried out. The average age, academic degree and discipline distribution of geologists, and issues related to geoscience education have been statistically studied, based on reclaimed questionnaires from over 40 universities, 8 research institutes of Chinese Academy of Sciences, 147 persons who have been funded by the National Natural Science Foundation of China (NSFC) as outstanding young scientists, and 407 project principals of NSFC youth fund projects. In China, 4 418 people are now engaged in the basic research of geosciences, with peak ages between 41 and 45 years. The number sharply decreases for geologists younger than 40 years. The ratio of the number of Ph D graduates in geology over the total number of Ph D graduates in China decreased from 8. 76% in 1993 to 4.7% in 2003. If the decline in the number of young geologists remains unchanged, the human resource in fundamental geological research would be not enough to meet the needs of the development of ESS and the progress of economy and society. In order to achieve the strategic goal for China to develop faster in geoscience studies, strategic measures are proposed on how to improve funding, the training and evaluation system and the socialacademic environment for young geologists.
To meet the requirements of Earth System Science (ESS) development in China, a state-of-the-art study has been carried out. The average age, academic degree and discipline distribution of geologists, and issues related to geoscience education have been statistically studied, based on reclaimed questionnaires from over 40 universities, 8 research institutes of Chinese Academy of Sciences, 147 persons who have been funded by the National Natural Science Foundation of China (NSFC) as outstanding young scientists, and 407 project principals of NSFC youth fund projects. In China, 4 418 people are now engaged in the basic research of geosciences, with peak ages between 41 and 45 years. The number sharply decreases for geologists younger than 40 years. The ratio of the number of Ph D graduates in geology over the total number of Ph D graduates in China decreased from 8. 76% in 1993 to 4.7% in 2003. If the decline in the number of young geologists remains unchanged, the human resource in fundamental geological research would be not enough to meet the needs of the development of ESS and the progress of economy and society. In order to achieve the strategic goal for China to develop faster in geoscience studies, strategic measures are proposed on how to improve funding, the training and evaluation system and the socialacademic environment for young geologists.
2006, 31(3): 330-336.
Abstract:
The formation process of the various energy resources coexisting system and its regional tectonic background in Ordos basin are analyzed by introducing the "metallogenic system" theory in this paper. The Mesozoic is the important transition period of the regional tectonic regime, during which the orogeny is outstanding around the basin and three rectothermal events took place in the basin. The transition of the tectonic regime induces the occurrence of various accumulating processes of the inorganic and organic fluids, for example, the organic fluid in the basin is activated by the recto-thermal events and the inorganic fluid flowing towards the basin is produced due to the orogeny. The reciprocity between the inorganic and organic fluids happens during their transporting. The existence of the organic fluid produces the redox barrier, which causes the mutation of the physicochemical parameters of the inorganic fluid and the precipitation of the uranium element at the interface. The mutation and interface effects are obvious in the formation of the various energy resources.
The formation process of the various energy resources coexisting system and its regional tectonic background in Ordos basin are analyzed by introducing the "metallogenic system" theory in this paper. The Mesozoic is the important transition period of the regional tectonic regime, during which the orogeny is outstanding around the basin and three rectothermal events took place in the basin. The transition of the tectonic regime induces the occurrence of various accumulating processes of the inorganic and organic fluids, for example, the organic fluid in the basin is activated by the recto-thermal events and the inorganic fluid flowing towards the basin is produced due to the orogeny. The reciprocity between the inorganic and organic fluids happens during their transporting. The existence of the organic fluid produces the redox barrier, which causes the mutation of the physicochemical parameters of the inorganic fluid and the precipitation of the uranium element at the interface. The mutation and interface effects are obvious in the formation of the various energy resources.
2006, 31(3): 337-348.
Abstract:
This paper introduces a new framework of mineral resource assessment according to the principle of multifractal modeling, particularly, Singularity, Generalized Self-Similarity and Fractal Spectrum (3S). It has been demonstrated that the concepts and models relevant to multifractal theory are useful not only for characterizing the fundamental properties of non-linearity of the mineralization processes, the singular distribution of mineral deposits and ore element concentrations in mineral districts, but also for singularity analysis and anomaly delineation. The theory can explain many properties of mineralization and spatial-temporal distribution spectra of mineral deposits such as mineral aggregation, singular distribution of element concentration, multifractal tonnage-grade model, fractal growth of minerals, and self-organized processes. Integrating multifractal principals, mineralization processes, distribution of mineral deposits, and resource assessment have resulted in an effective new approach for mapping mineral resources and modeling mineral targets. Together with the advanced GeoDAS GIS technology it serves as a novel principal methodology and technology for mineral resource assessment.
This paper introduces a new framework of mineral resource assessment according to the principle of multifractal modeling, particularly, Singularity, Generalized Self-Similarity and Fractal Spectrum (3S). It has been demonstrated that the concepts and models relevant to multifractal theory are useful not only for characterizing the fundamental properties of non-linearity of the mineralization processes, the singular distribution of mineral deposits and ore element concentrations in mineral districts, but also for singularity analysis and anomaly delineation. The theory can explain many properties of mineralization and spatial-temporal distribution spectra of mineral deposits such as mineral aggregation, singular distribution of element concentration, multifractal tonnage-grade model, fractal growth of minerals, and self-organized processes. Integrating multifractal principals, mineralization processes, distribution of mineral deposits, and resource assessment have resulted in an effective new approach for mapping mineral resources and modeling mineral targets. Together with the advanced GeoDAS GIS technology it serves as a novel principal methodology and technology for mineral resource assessment.
2006, 31(3): 349-354.
Abstract:
The Qulong porphyry copper deposit is the largest recently found in the Gangdise metallogenic belt. It was formed in the Miocene. The original fluid inclusions can be divided into five types according to the compositions of liquid, gas and single minerals The temperature of the main ore-forming phase ranges from 240 to 650 ℃ and the salinity is about 0.18wt.%-52.04wt.%. The fluids can be classified into two types including high salinity and high density, low salinity and low density. Daughter mineral inclusions, liquid and gas inclusions are coexistent and their homogeneous temperature is approximate, however salinity is quite different, showing that the fluid underwent the process of boiling. A study of the H and O isotopes and trace and rare elements of a single mineral indicates that the mineralization substance comes from the system of porphyry magma and fluid belonging to the NaCl (F) -KCl (F) -C2H6-HCO3-CaSO4 type fluid, which comes from magma and natural hot-brine. The fluid is characteristically reducing and acid, with high temperature, high salinity, high mineralization degree, and high oxygen fugacity.The fluid has high concentrations of Na+, K+, Cl-, SO42-, CO2 etc., with high F-(F-/Cl- > 1, average 5.66), which was good for the transfer of Fe2+ and Cu2+, finally concentrated and formed the deposit, and is the necessary condition for the Qulong super-large porphyry copper deposit to form. Decompression and the mixing of different quality fluids is the main mechanism for the depositing of metalions. The mineralizated depth is also discussed and could be regarded as the prospecting base of mineral deposit.
The Qulong porphyry copper deposit is the largest recently found in the Gangdise metallogenic belt. It was formed in the Miocene. The original fluid inclusions can be divided into five types according to the compositions of liquid, gas and single minerals The temperature of the main ore-forming phase ranges from 240 to 650 ℃ and the salinity is about 0.18wt.%-52.04wt.%. The fluids can be classified into two types including high salinity and high density, low salinity and low density. Daughter mineral inclusions, liquid and gas inclusions are coexistent and their homogeneous temperature is approximate, however salinity is quite different, showing that the fluid underwent the process of boiling. A study of the H and O isotopes and trace and rare elements of a single mineral indicates that the mineralization substance comes from the system of porphyry magma and fluid belonging to the NaCl (F) -KCl (F) -C2H6-HCO3-CaSO4 type fluid, which comes from magma and natural hot-brine. The fluid is characteristically reducing and acid, with high temperature, high salinity, high mineralization degree, and high oxygen fugacity.The fluid has high concentrations of Na+, K+, Cl-, SO42-, CO2 etc., with high F-(F-/Cl- > 1, average 5.66), which was good for the transfer of Fe2+ and Cu2+, finally concentrated and formed the deposit, and is the necessary condition for the Qulong super-large porphyry copper deposit to form. Decompression and the mixing of different quality fluids is the main mechanism for the depositing of metalions. The mineralizated depth is also discussed and could be regarded as the prospecting base of mineral deposit.
2006, 31(3): 355-360.
Abstract:
Recently the microbial mineral exploration method, spore counting of Bacillus cereus in soil samples which is indicative for blind gold ore deposit, has been confirmed by many geologists in different countries. However, the identification of bacterial strains, indicators for gold mineralization, was still done through the culturing method in previous studies. This paper employed molecular biology technique to microbial identification in mineralized areas. Two bacterial strains as indicators of gold mineralization were randomly isolated from the gold deposit of Shewu mountain in Jiayu county, Hubei Province. On the basis of biochemical and physiological identification, phylogenetic analysis dedrived from 16S rDNA and 16S-23S rDNA sequence, strains Y1 and Y2 were identified as Bacillus mycoides and B. cereus respectively, both of which belong to "B. cereus group". So it is "B. cereus group" that is the indicator for gold mineralization instead of B. ceresus species. The results assured the reliability of the traditional selective culturing method of B. cereus group, and the feasibility of molecular biology techniques on mineral exploration. In addition, 16S rDNA and 16S-23S rDNA sequence analyses were helpful to make fluorogenic-probe reagent box in future work.
Recently the microbial mineral exploration method, spore counting of Bacillus cereus in soil samples which is indicative for blind gold ore deposit, has been confirmed by many geologists in different countries. However, the identification of bacterial strains, indicators for gold mineralization, was still done through the culturing method in previous studies. This paper employed molecular biology technique to microbial identification in mineralized areas. Two bacterial strains as indicators of gold mineralization were randomly isolated from the gold deposit of Shewu mountain in Jiayu county, Hubei Province. On the basis of biochemical and physiological identification, phylogenetic analysis dedrived from 16S rDNA and 16S-23S rDNA sequence, strains Y1 and Y2 were identified as Bacillus mycoides and B. cereus respectively, both of which belong to "B. cereus group". So it is "B. cereus group" that is the indicator for gold mineralization instead of B. ceresus species. The results assured the reliability of the traditional selective culturing method of B. cereus group, and the feasibility of molecular biology techniques on mineral exploration. In addition, 16S rDNA and 16S-23S rDNA sequence analyses were helpful to make fluorogenic-probe reagent box in future work.
2006, 31(3): 361-365.
Abstract:
Quantifying the degree of quartz mylonite deformation, including the irregularities of the frequency distribution of the minerals involved, is one of the most challenging areas in mylonite analysis. Fractal modelling is here demonstrated to be an effective means to achieve this goal. The P-A (perimeter-area) model is used to quantify the irregularities of quartz, the main mineral component of mylonite, in the geometries. Five types of mylonites with different degrees of deformation within the foreland of the Moine thrust zone in NW Scotland were selected. The quartz was extracted from digital photomicrographs of multiscale-grey image grid data, and converted into vector data. The areas and perimeters of these quartz grains were calculated by GIS-based technologies. There is an increase in the degree of deformation of mylonite from type 1 to type 5, a D_ AP (the perimeter-area fractal dimension) increase from 1.20, 1.28, 1.38, 1.46 to 1.60, respectively. The results indicate quantitatively that quartz grains change from a regular to an irregular shape.
Quantifying the degree of quartz mylonite deformation, including the irregularities of the frequency distribution of the minerals involved, is one of the most challenging areas in mylonite analysis. Fractal modelling is here demonstrated to be an effective means to achieve this goal. The P-A (perimeter-area) model is used to quantify the irregularities of quartz, the main mineral component of mylonite, in the geometries. Five types of mylonites with different degrees of deformation within the foreland of the Moine thrust zone in NW Scotland were selected. The quartz was extracted from digital photomicrographs of multiscale-grey image grid data, and converted into vector data. The areas and perimeters of these quartz grains were calculated by GIS-based technologies. There is an increase in the degree of deformation of mylonite from type 1 to type 5, a D_ AP (the perimeter-area fractal dimension) increase from 1.20, 1.28, 1.38, 1.46 to 1.60, respectively. The results indicate quantitatively that quartz grains change from a regular to an irregular shape.
2006, 31(3): 366-371.
Abstract:
Middle-Upper Ordovician sequence stratigraphy and sedimentary evolution are studied based on the interpretation of regional seismic data in west Tadong uplift, Tarim basin, Northwest China. Two seismic sequences are identified in the Middle-Upper Ordovician, and a group of seismic reflection units with mounded geometry and clinoforms are confirmed as stacked submarine fan deposits calibrated by cores and lithological logs. The submarine fan deposits mainly consist of seven types of lithofacies, which are massive conglomerates and sandstones, normal-graded sandstones and siltstones, parallel- bedded sandstones and siltstones, rippled siltstones, convolute siltstones, horizontal-laminated silty shales, and massive or graded shales, respectively. The submarine fans were sourced from the Middle-Late Ordovician island arcs located to the south of our study area. The findings of this study are significant to hydrocarbon exploration in the Tarim basin.
Middle-Upper Ordovician sequence stratigraphy and sedimentary evolution are studied based on the interpretation of regional seismic data in west Tadong uplift, Tarim basin, Northwest China. Two seismic sequences are identified in the Middle-Upper Ordovician, and a group of seismic reflection units with mounded geometry and clinoforms are confirmed as stacked submarine fan deposits calibrated by cores and lithological logs. The submarine fan deposits mainly consist of seven types of lithofacies, which are massive conglomerates and sandstones, normal-graded sandstones and siltstones, parallel- bedded sandstones and siltstones, rippled siltstones, convolute siltstones, horizontal-laminated silty shales, and massive or graded shales, respectively. The submarine fans were sourced from the Middle-Late Ordovician island arcs located to the south of our study area. The findings of this study are significant to hydrocarbon exploration in the Tarim basin.
Rebuilding Paleogeomorphology of Pre-Jurassic and Oil-Gas Accumulation Regulation in Zhoujiawan Area
2006, 31(3): 372-377.
Abstract:
Pre-Jurassic paleogeomorphology controls not only the deposit and development of the Early Jurassic but also oilgas accumulation regulation. It is important to rebuild the paleogeomorphology accurately for oil-gas exploration of the Jurassic. Taking the Zhoujiawan area in the Ordos basin as an example and using 3D reservoir modeling techniques and an interpretation of the geology, drilling and logging, this paper rebuilds the paleogeomorphology of the pre-Jurassic based on analyses of sedimentary facies, sand body, flow direction, paleoburial depth reconstruction and paleobathymetric correction. At the same time, 3D sand body, porosity and permeability models are built. Using oil-gas reservoir forming conditions such as generating, storing, covering, trapping, migrating and preserving, the model visually interprets the regulations of oil-gas accumulation. According to the above models, favorable hydrocarbon accumulation areas are forecasted. They are located on the sand body of river marginal banks and the channel bars of river valleys on the three ramp reservoir regions. The models offer reliable evidence for exploratory development.
Pre-Jurassic paleogeomorphology controls not only the deposit and development of the Early Jurassic but also oilgas accumulation regulation. It is important to rebuild the paleogeomorphology accurately for oil-gas exploration of the Jurassic. Taking the Zhoujiawan area in the Ordos basin as an example and using 3D reservoir modeling techniques and an interpretation of the geology, drilling and logging, this paper rebuilds the paleogeomorphology of the pre-Jurassic based on analyses of sedimentary facies, sand body, flow direction, paleoburial depth reconstruction and paleobathymetric correction. At the same time, 3D sand body, porosity and permeability models are built. Using oil-gas reservoir forming conditions such as generating, storing, covering, trapping, migrating and preserving, the model visually interprets the regulations of oil-gas accumulation. According to the above models, favorable hydrocarbon accumulation areas are forecasted. They are located on the sand body of river marginal banks and the channel bars of river valleys on the three ramp reservoir regions. The models offer reliable evidence for exploratory development.
2006, 31(3): 378-383.
Abstract:
The increase of crude oil viscosity can affect the production performance of oil fields when they are flooded by injection water. To study this effect, oil viscosity was analyzed statistically and its increase model was regressed. Based on the three-dimensional and three-phase black-oil model, a new mathematical model considering the change of oil viscosity caused by other factors besides formation pressure was developed. The model was discretized by the finite-difference method and solved by the LSOR (line successive over relaxation) method. A new numerical simulator written in Fortran 90 codes was developed. An oil field example of changes in oil viscosity is studied using the numerical simulator, and the changes in oil viscosity and their effects on water drive performance were studied and compared with the results given by a normal simulator. The result shows that oil recovery (water-cut arrives to 98%) decreases from 44. 80% to 34. 29% when the viscosity factor increases from 0 to 0. 02 if the initial viscosity ratio of water to oil is 1 : 10. The recovery predicted by current commercial oil reservoir simulators that neglect the increase in oil viscosity with water-cut rising is higher than true recovery.
The increase of crude oil viscosity can affect the production performance of oil fields when they are flooded by injection water. To study this effect, oil viscosity was analyzed statistically and its increase model was regressed. Based on the three-dimensional and three-phase black-oil model, a new mathematical model considering the change of oil viscosity caused by other factors besides formation pressure was developed. The model was discretized by the finite-difference method and solved by the LSOR (line successive over relaxation) method. A new numerical simulator written in Fortran 90 codes was developed. An oil field example of changes in oil viscosity is studied using the numerical simulator, and the changes in oil viscosity and their effects on water drive performance were studied and compared with the results given by a normal simulator. The result shows that oil recovery (water-cut arrives to 98%) decreases from 44. 80% to 34. 29% when the viscosity factor increases from 0 to 0. 02 if the initial viscosity ratio of water to oil is 1 : 10. The recovery predicted by current commercial oil reservoir simulators that neglect the increase in oil viscosity with water-cut rising is higher than true recovery.
2006, 31(3): 384-388.
Abstract:
The limit of the current scenario-based software architecture evaluation (SAE) is not taken into account the knowledge reuse of SAE. A new reused-based software architecture evaluation pattern, which includes meta-model and application framework, is proposed in this paper for integrating the SAE into a systematic and reusable procedure. Exploiting the meta-model and the application framework of SAE can make decision of SAE in high-level and reuse the historic data of SAE. Finally, this pattern is successfully applied and validated in the software architecture of the ground system for data, research and application of lunar exploration program of China. The pattern reduces the research risk of deep-space exploration complex system.
The limit of the current scenario-based software architecture evaluation (SAE) is not taken into account the knowledge reuse of SAE. A new reused-based software architecture evaluation pattern, which includes meta-model and application framework, is proposed in this paper for integrating the SAE into a systematic and reusable procedure. Exploiting the meta-model and the application framework of SAE can make decision of SAE in high-level and reuse the historic data of SAE. Finally, this pattern is successfully applied and validated in the software architecture of the ground system for data, research and application of lunar exploration program of China. The pattern reduces the research risk of deep-space exploration complex system.
2006, 31(3): 389-393.
Abstract:
This paper proposes an extended version of the fuzzy weights of evidence method, based on the fuzzy training layer for assessing and predicting the occurrence of area-events. It can be considered as a generalization of the ordinary weights of evidence method, which is used to predict the occurrence of point-events with known evidences and training layers. Unlike the ordinary weights of evidence using point training sets, the new method involves training data as a fuzzy set. Point training data can be converted to a fuzzy set, therefore the new method can predict both point-events and area-events. When both evidence and training data are fuzzy sets, the new method acts as a dual fuzzy weights of evidence method. A case study has been used to demonstrate the application of the method in assessing desertification in the area in the contact of Shanxi and Shaanxi Provinces and Inner Mongolia Autonomous Region.
This paper proposes an extended version of the fuzzy weights of evidence method, based on the fuzzy training layer for assessing and predicting the occurrence of area-events. It can be considered as a generalization of the ordinary weights of evidence method, which is used to predict the occurrence of point-events with known evidences and training layers. Unlike the ordinary weights of evidence using point training sets, the new method involves training data as a fuzzy set. Point training data can be converted to a fuzzy set, therefore the new method can predict both point-events and area-events. When both evidence and training data are fuzzy sets, the new method acts as a dual fuzzy weights of evidence method. A case study has been used to demonstrate the application of the method in assessing desertification in the area in the contact of Shanxi and Shaanxi Provinces and Inner Mongolia Autonomous Region.
2006, 31(3): 394-398.
Abstract:
The utilization of closed loop, which generates power by combining the geothermal system with solar energy system, is feasible to solve energetic problem and to exploit renewable energy. The power generation system can avoid such environmental problems as earthquake, heat pollution, ground sedimentation, decrease of geothermal water resources, toxicant pollution, caused by mass use of geothermal water resources. Moreover, the system is expected to be free of the limitation of the geographic location. The technology is to generate power by taking the advantage of the closed loop which combines the geothermal system with solar energy system. The geothermal system is suitable for ORC power generation since the vertical depth of the underground part is 3-5 km, horizontal distance is around 5-7 km, and the fluid temperature in the horizontal well comes to around 150 ℃. Trough paraboloid mirror is used in the solar energy system to collect heat in which either water or oil is feasible as heat collecting fluid, and it is possible for temperature to reach as high as or even higher than 350 ℃. Primary circulation media is water and the secondary one is isobutane. The maximal power generation productivity of ORC is 20% in the daytime and 12% at night. Chemical storage energy is adopted in the system which has a storage-density 10 times higher than the apparent-heat storage energy and the potential-heat one. The system is proved to be feasible after studying the relative technologies of drilling and completion, the transformation from solar energy to heat energy, heat-carrier fluid, ORC and storage energy.
The utilization of closed loop, which generates power by combining the geothermal system with solar energy system, is feasible to solve energetic problem and to exploit renewable energy. The power generation system can avoid such environmental problems as earthquake, heat pollution, ground sedimentation, decrease of geothermal water resources, toxicant pollution, caused by mass use of geothermal water resources. Moreover, the system is expected to be free of the limitation of the geographic location. The technology is to generate power by taking the advantage of the closed loop which combines the geothermal system with solar energy system. The geothermal system is suitable for ORC power generation since the vertical depth of the underground part is 3-5 km, horizontal distance is around 5-7 km, and the fluid temperature in the horizontal well comes to around 150 ℃. Trough paraboloid mirror is used in the solar energy system to collect heat in which either water or oil is feasible as heat collecting fluid, and it is possible for temperature to reach as high as or even higher than 350 ℃. Primary circulation media is water and the secondary one is isobutane. The maximal power generation productivity of ORC is 20% in the daytime and 12% at night. Chemical storage energy is adopted in the system which has a storage-density 10 times higher than the apparent-heat storage energy and the potential-heat one. The system is proved to be feasible after studying the relative technologies of drilling and completion, the transformation from solar energy to heat energy, heat-carrier fluid, ORC and storage energy.
2006, 31(3): 399-404.
Abstract:
Two short cores were obtained from a tree nursery in eastern Beijing city, and gray-black pollutants can be found within the uppermost 37 cm of the soil profile. All of them were measured, and one of them, profile BJ722 of 90 cm length, is discussed in detail in this paper. Magnetic measurements, element contents and grain size analysis were carried out to understand the vertical characteristics of magnetic minerals and heavy metals in soil from anthropogenic pollutants, as well as the relationship between magnetic parameters and heavy metals. Magnetic proxies show similar pattern comparing to heavy metal elements, with higher concentration above 37 cm. Index cluster and principal component analysis indicate that strong correlation between magnetic parameters and Pb, Zn, Sr, Ba and Cu (R2 > 0.90, membership > 80%). Fuzzy C-means cluster analysis (FCM) shows that anthropogenic pollutants accumulated and enriched above 37 cm. Below 37 cm, soil is unpolluted. Our work demonstrates that magnetic measurements can be used to delineate anthropogenic pollution in the soil profile and to identify the migration depth and the depth of unpolluted soil with the help of multivariate statistics.
Two short cores were obtained from a tree nursery in eastern Beijing city, and gray-black pollutants can be found within the uppermost 37 cm of the soil profile. All of them were measured, and one of them, profile BJ722 of 90 cm length, is discussed in detail in this paper. Magnetic measurements, element contents and grain size analysis were carried out to understand the vertical characteristics of magnetic minerals and heavy metals in soil from anthropogenic pollutants, as well as the relationship between magnetic parameters and heavy metals. Magnetic proxies show similar pattern comparing to heavy metal elements, with higher concentration above 37 cm. Index cluster and principal component analysis indicate that strong correlation between magnetic parameters and Pb, Zn, Sr, Ba and Cu (R2 > 0.90, membership > 80%). Fuzzy C-means cluster analysis (FCM) shows that anthropogenic pollutants accumulated and enriched above 37 cm. Below 37 cm, soil is unpolluted. Our work demonstrates that magnetic measurements can be used to delineate anthropogenic pollution in the soil profile and to identify the migration depth and the depth of unpolluted soil with the help of multivariate statistics.
2006, 31(3): 405-410.
Abstract:
In order to efficiently obtain high-quality quantitative parameters in active tectonics research, it is necessary to introduce digital aerophotogrammetry as a surveying and mapping tool. Testing research was performed along the Xianshuihe fault zone, which is located in the mountain area of western Sichuan Province. Using spatially enhanced, orthorectified images, large scale topography and ground surface profiles, we obtained a series of data of the active Xianshuihe fault zone near Tuanjie in the south of Kangding county. Left lateral horizontal deformation of the fault is about 43 m and vertical deformation is about 5.8 m since the T1 proluvial fan was formed. Digital aerophotogrammetry provides high precision when measuring quantitative parameters in the study of active tectonics such as accumulative horizontal and vertical deformations and fault length, detailed geometric structure resolution and geomorphological mapping, thus greatly improving field work efficiency.
In order to efficiently obtain high-quality quantitative parameters in active tectonics research, it is necessary to introduce digital aerophotogrammetry as a surveying and mapping tool. Testing research was performed along the Xianshuihe fault zone, which is located in the mountain area of western Sichuan Province. Using spatially enhanced, orthorectified images, large scale topography and ground surface profiles, we obtained a series of data of the active Xianshuihe fault zone near Tuanjie in the south of Kangding county. Left lateral horizontal deformation of the fault is about 43 m and vertical deformation is about 5.8 m since the T1 proluvial fan was formed. Digital aerophotogrammetry provides high precision when measuring quantitative parameters in the study of active tectonics such as accumulative horizontal and vertical deformations and fault length, detailed geometric structure resolution and geomorphological mapping, thus greatly improving field work efficiency.
2006, 31(3): 411-416.
Abstract:
The dissolution rate-determining processes of carbonate rocks include: (1) heterogeneous reactions on rock surface; (2) mass transport of ions into solution from rock surface via diffusion; and (3) conversion reaction of CO2 into H+ and HCO3-. Generally, it is the slowest of these three processes that limits the dissolution rate of carbonate rock. However, it was found from experiments and theoretical analysis that under similar conditions, not only are the initial dissolution rates of dolomite lower by a factor of 3 to 60 than those of limestone, but also there are different dissolution rate-determining mechanisms between limestone and dolomite. For example, under conditions of CO2 partial pressures (pCO2) >100 Pa, limestone dissolution rates increase remarkably, by a factor of about 10 after the addition of carbonic anhydrase (CA) into the solution, which catalyzes the conversion reaction of CO 2. For dolomite, the increase of dissolution rate after the addition of CA appears at pCO2 < 10 000 Pa. The enhancement factor of CA on dolomite dissolution rates is much lower (a factor of only about 3). In addition, though dissolution of both limestone and dolomite is also determined by hydrodynamics (rotation speed or flow speed), especially under pCO2 < 1 000 Pa, the dissolution of limestone is more sensitive to hydrodynamic change than the dissolution of dolomite. These findings are of significance in understanding the differences in karstification and relevant problems of resources and environments of dolomite and limestone areas.
The dissolution rate-determining processes of carbonate rocks include: (1) heterogeneous reactions on rock surface; (2) mass transport of ions into solution from rock surface via diffusion; and (3) conversion reaction of CO2 into H+ and HCO3-. Generally, it is the slowest of these three processes that limits the dissolution rate of carbonate rock. However, it was found from experiments and theoretical analysis that under similar conditions, not only are the initial dissolution rates of dolomite lower by a factor of 3 to 60 than those of limestone, but also there are different dissolution rate-determining mechanisms between limestone and dolomite. For example, under conditions of CO2 partial pressures (pCO2) >100 Pa, limestone dissolution rates increase remarkably, by a factor of about 10 after the addition of carbonic anhydrase (CA) into the solution, which catalyzes the conversion reaction of CO 2. For dolomite, the increase of dissolution rate after the addition of CA appears at pCO2 < 10 000 Pa. The enhancement factor of CA on dolomite dissolution rates is much lower (a factor of only about 3). In addition, though dissolution of both limestone and dolomite is also determined by hydrodynamics (rotation speed or flow speed), especially under pCO2 < 1 000 Pa, the dissolution of limestone is more sensitive to hydrodynamic change than the dissolution of dolomite. These findings are of significance in understanding the differences in karstification and relevant problems of resources and environments of dolomite and limestone areas.
2006, 31(3): 417-422.
Abstract:
Ziyili Hydropower Station in Sichuan Province uses an equalized room fitted with atmoseal, which needs a more precise investigation on the permeability of rock masses around the power house. This paper proposes an effective method that systematically characterizes the permeability of rock masses, from qualitative analyses to quantitative analyses. Based on a study of basic geology and hydrogeology conditions, we measured the geometric parameters of fractures (such as orientation, aperture, trace length, space and fracture frequency) and obtained their characteristic statistical values. We then calculated the main value and comprehensive value of the permeability tensor using permeability tensor theory, and finally divided the rock masses around the power house into a few permeability subareas. The general permeability of the rock masses around the power house varies with depth and the local permeability varies alternately between the higher and the lower due to the effect of the contact strip. The permeability can be divided into three grades. The permeability of rock masses near the surface is higher (n×100 m/d~n×10-1 m/d) and permeability of rock masses around the equalized room with atmoseal is moderate to lower (n×10-2 m/d~n×10-4 m/d).
Ziyili Hydropower Station in Sichuan Province uses an equalized room fitted with atmoseal, which needs a more precise investigation on the permeability of rock masses around the power house. This paper proposes an effective method that systematically characterizes the permeability of rock masses, from qualitative analyses to quantitative analyses. Based on a study of basic geology and hydrogeology conditions, we measured the geometric parameters of fractures (such as orientation, aperture, trace length, space and fracture frequency) and obtained their characteristic statistical values. We then calculated the main value and comprehensive value of the permeability tensor using permeability tensor theory, and finally divided the rock masses around the power house into a few permeability subareas. The general permeability of the rock masses around the power house varies with depth and the local permeability varies alternately between the higher and the lower due to the effect of the contact strip. The permeability can be divided into three grades. The permeability of rock masses near the surface is higher (n×100 m/d~n×10-1 m/d) and permeability of rock masses around the equalized room with atmoseal is moderate to lower (n×10-2 m/d~n×10-4 m/d).
2006, 31(3): 423-426.
Abstract:
In order to design optimally and apply rationally a single pipe ejector, this paper describes the structural and application characteristics of a single pipe ejector system. The basic optimum formulae are created between the parameter relationships of dewatering depth and the size of the ejector, and the performance of the centrifugal pump. It is simple and convenient to select the performance parameters of the centrifugal pump and design a single pipe ejector system according to dewatering depth and yield, and to calculate the yield of the dewatering depth through the ejector and design a deep foundation dewatering system.
In order to design optimally and apply rationally a single pipe ejector, this paper describes the structural and application characteristics of a single pipe ejector system. The basic optimum formulae are created between the parameter relationships of dewatering depth and the size of the ejector, and the performance of the centrifugal pump. It is simple and convenient to select the performance parameters of the centrifugal pump and design a single pipe ejector system according to dewatering depth and yield, and to calculate the yield of the dewatering depth through the ejector and design a deep foundation dewatering system.
