2023 Vol.6(3)
Display Method: |
2023, 6(3):369-382.
doi: 10.31035/cg2022062
Abstract:
To illuminate the spatio-temporal variation characteristics and geochemical driving mechanism of soil pH in the Nenjiang River Basin, the National Multi-objective Regional Geochemical Survey data of topsoil, the Second National Soil Survey data and Normalized Difference Vegetation Index (NDVI) were analyzed. The areas of neutral and alkaline soil decreased by 21100 km2 and 30500 km2, respectively, while that of strongly alkaline, extremely alkaline, and strongly acidic soil increased by 19600 km2, 18200 km2, and 15500 km2, respectively, during the past 30 years. NDVI decreased with the increase of soil pH when soil pH > 8.0, and it was reversed when soil pH < 5.0. There were significant differences in soil pH with various surface cover types, which showed an ascending order: Arbor < reed < maize < rice < high and medium-covered meadow < low-covered meadow < Puccinellia. The weathering products of minerals rich in K2O, Na2O, CaO, and MgO entered into the low plain and were enriched in different parts by water transportation and lake deposition, while Fe and Al remained in the low hilly areas, which was the geochemical driving mechanism. The results of this study will provide scientific basis for making scientific and rational decisions on soil acidification and salinization.
To illuminate the spatio-temporal variation characteristics and geochemical driving mechanism of soil pH in the Nenjiang River Basin, the National Multi-objective Regional Geochemical Survey data of topsoil, the Second National Soil Survey data and Normalized Difference Vegetation Index (NDVI) were analyzed. The areas of neutral and alkaline soil decreased by 21100 km2 and 30500 km2, respectively, while that of strongly alkaline, extremely alkaline, and strongly acidic soil increased by 19600 km2, 18200 km2, and 15500 km2, respectively, during the past 30 years. NDVI decreased with the increase of soil pH when soil pH > 8.0, and it was reversed when soil pH < 5.0. There were significant differences in soil pH with various surface cover types, which showed an ascending order: Arbor < reed < maize < rice < high and medium-covered meadow < low-covered meadow < Puccinellia. The weathering products of minerals rich in K2O, Na2O, CaO, and MgO entered into the low plain and were enriched in different parts by water transportation and lake deposition, while Fe and Al remained in the low hilly areas, which was the geochemical driving mechanism. The results of this study will provide scientific basis for making scientific and rational decisions on soil acidification and salinization.
2023, 6(3):383-394.
doi: 10.31035/cg2022073
Abstract:
To reveal the microbial community composition of regional shallow porous brackish groundwater and its response characteristics to groundwater environment, the first and second aquifers in Taocheng District, Hengshui City were selected, and 10 groundwater source samples were collected for hydrochemical analysis and microbial 16S RNA gene V4–V5 regional sequencing. The results showed that the shallow brackish groundwater in the study area is weakly alkaline and has high ion content. The hydrochemical types are SO4·Cl-Na·Mg type and HCO3·Cl-Na·Mg type as a whole. The spatial zonation of the abundance and diversity of groundwater microorganisms is obvious. The number of endemic bacteria in groundwater from upstream, midstream to downstream is 11, 135 and 22 respectively, with a total of 22 bacteria. Proteobacteria is the most dominant in groundwater level (38.82%–86.88%), and there are obvious differences in different sections. At the genus level, the main dominant species in each group and sample are Pseudomonas and Hydrogenophaga. In terms of composition difference, Pseudohongiella, Pseudorhodobacter and Limnohabitans are the representatives of UR, MR and LR. On the whole, the composition of flora in groundwater in the study area is sensitive and closely related to hydrochemical processes. Species abundance is affected by alkaline and high salinity environmental indicators, while species diversity is related to depth and dissolved oxygen in weak reduction environment.
To reveal the microbial community composition of regional shallow porous brackish groundwater and its response characteristics to groundwater environment, the first and second aquifers in Taocheng District, Hengshui City were selected, and 10 groundwater source samples were collected for hydrochemical analysis and microbial 16S RNA gene V4–V5 regional sequencing. The results showed that the shallow brackish groundwater in the study area is weakly alkaline and has high ion content. The hydrochemical types are SO4·Cl-Na·Mg type and HCO3·Cl-Na·Mg type as a whole. The spatial zonation of the abundance and diversity of groundwater microorganisms is obvious. The number of endemic bacteria in groundwater from upstream, midstream to downstream is 11, 135 and 22 respectively, with a total of 22 bacteria. Proteobacteria is the most dominant in groundwater level (38.82%–86.88%), and there are obvious differences in different sections. At the genus level, the main dominant species in each group and sample are Pseudomonas and Hydrogenophaga. In terms of composition difference, Pseudohongiella, Pseudorhodobacter and Limnohabitans are the representatives of UR, MR and LR. On the whole, the composition of flora in groundwater in the study area is sensitive and closely related to hydrochemical processes. Species abundance is affected by alkaline and high salinity environmental indicators, while species diversity is related to depth and dissolved oxygen in weak reduction environment.
2023, 6(3):395-408.
doi: 10.31035/cg2022075
Abstract:
The Luan River is the most important water system in north-eastern Hebei Province, China and is located in the transitional zone of the Eastern Yan Mountains, North China Plain and Songliao Plain. The well-developed river terraces of its tributary, the Yixun River, provide excellent information for studying neotectonics and climate change. There are seven terraces in the lower reaches of the Yixun River, numbered T7–T1. The optically stimulated luminescence dating results of 23 samples show that terraces T7–T2 formed at 111.36±5.83 ka, 78.20±4.45 ka, 65.29±4.15 ka, 56.44±3.07 ka, 40.08±2.66 ka, and 13.14±0.76 ka, respectively. A comparison with the oxygen isotope curves of deep-sea sediments reveals that the sediment formation of each terrace corresponded to cold periods of marine isotope stages MIS 4 and MIS 2 and the relatively cold periods of MIS 5e, MIS 3, and MIS 1. Since the Late Pleistocene, the incision rate of the Yixun River has ranged from 0.371–1.740 mm/a. During the formation of T7–T6, T5–T4, T4–T3, and T3–T2, the incision rate was low. However, in the two stages during which T6–T5 and T2–T1 formed (13.14±0.76 ka to 0.58±0.08 ka and 10.79±0.64 ka to 0.16±0.01 ka), these rates reached 1.554 mm/a and 1.592–1.740 mm/a, respectively. At approximately 30 ka, the activity of the Langying Fault increased, leading to footwall uplift. The river gathered in the north of Langying to form the ancient Erdaowan Lake, which resulted in the drying of the river in the lower reaches of the Yixun River during the last glacial maximum without forming river deposits. In the Early Holocene, headward erosion in the lower reaches of the Yixun River was enhanced, which resulted in the disappearance of the lake, and incised meandering formed due to increased neotectonism. Based on the analyses of river incision and the formation of ancient lakes and incised meandering, it was inferred that there have been three periods of strong tectonism in the river basin since the Late Pleistocene.
The Luan River is the most important water system in north-eastern Hebei Province, China and is located in the transitional zone of the Eastern Yan Mountains, North China Plain and Songliao Plain. The well-developed river terraces of its tributary, the Yixun River, provide excellent information for studying neotectonics and climate change. There are seven terraces in the lower reaches of the Yixun River, numbered T7–T1. The optically stimulated luminescence dating results of 23 samples show that terraces T7–T2 formed at 111.36±5.83 ka, 78.20±4.45 ka, 65.29±4.15 ka, 56.44±3.07 ka, 40.08±2.66 ka, and 13.14±0.76 ka, respectively. A comparison with the oxygen isotope curves of deep-sea sediments reveals that the sediment formation of each terrace corresponded to cold periods of marine isotope stages MIS 4 and MIS 2 and the relatively cold periods of MIS 5e, MIS 3, and MIS 1. Since the Late Pleistocene, the incision rate of the Yixun River has ranged from 0.371–1.740 mm/a. During the formation of T7–T6, T5–T4, T4–T3, and T3–T2, the incision rate was low. However, in the two stages during which T6–T5 and T2–T1 formed (13.14±0.76 ka to 0.58±0.08 ka and 10.79±0.64 ka to 0.16±0.01 ka), these rates reached 1.554 mm/a and 1.592–1.740 mm/a, respectively. At approximately 30 ka, the activity of the Langying Fault increased, leading to footwall uplift. The river gathered in the north of Langying to form the ancient Erdaowan Lake, which resulted in the drying of the river in the lower reaches of the Yixun River during the last glacial maximum without forming river deposits. In the Early Holocene, headward erosion in the lower reaches of the Yixun River was enhanced, which resulted in the disappearance of the lake, and incised meandering formed due to increased neotectonism. Based on the analyses of river incision and the formation of ancient lakes and incised meandering, it was inferred that there have been three periods of strong tectonism in the river basin since the Late Pleistocene.
2023, 6(3):409-419.
doi: 10.31035/cg2023013
Abstract:
Landslide is a serious natural disaster next only to earthquake and flood, which will cause a great threat to people’s lives and property safety. The traditional research of landslide disaster based on experience-driven or statistical model and its assessment results are subjective , difficult to quantify, and no pertinence. As a new research method for landslide susceptibility assessment, machine learning can greatly improve the landslide susceptibility model’s accuracy by constructing statistical models. Taking Western Henan for example, the study selected 16 landslide influencing factors such as topography, geological environment, hydrological conditions, and human activities, and 11 landslide factors with the most significant influence on the landslide were selected by the recursive feature elimination (RFE) method. Five machine learning methods [Support Vector Machines (SVM), Logistic Regression (LR), Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Linear Discriminant Analysis (LDA)] were used to construct the spatial distribution model of landslide susceptibility. The models were evaluated by the receiver operating characteristic curve and statistical index. After analysis and comparison, the XGBoost model (AUC 0.8759) performed the best and was suitable for dealing with regression problems. The model had a high adaptability to landslide data. According to the landslide susceptibility map of the five models, the overall distribution can be observed. The extremely high and high susceptibility areas are distributed in the Funiu Mountain range in the southwest, the Xiaoshan Mountain range in the west, and the Yellow River Basin in the north. These areas have large terrain fluctuations, complicated geological structural environments and frequent human engineering activities. The extremely high and highly prone areas were 12043.3 km2 and 3087.45 km2, accounting for 47.61% and 12.20% of the total area of the study area, respectively. Our study reflects the distribution of landslide susceptibility in western Henan Province, which provides a scientific basis for regional disaster warning, prediction, and resource protection. The study has important practical significance for subsequent landslide disaster management.
Landslide is a serious natural disaster next only to earthquake and flood, which will cause a great threat to people’s lives and property safety. The traditional research of landslide disaster based on experience-driven or statistical model and its assessment results are subjective , difficult to quantify, and no pertinence. As a new research method for landslide susceptibility assessment, machine learning can greatly improve the landslide susceptibility model’s accuracy by constructing statistical models. Taking Western Henan for example, the study selected 16 landslide influencing factors such as topography, geological environment, hydrological conditions, and human activities, and 11 landslide factors with the most significant influence on the landslide were selected by the recursive feature elimination (RFE) method. Five machine learning methods [Support Vector Machines (SVM), Logistic Regression (LR), Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Linear Discriminant Analysis (LDA)] were used to construct the spatial distribution model of landslide susceptibility. The models were evaluated by the receiver operating characteristic curve and statistical index. After analysis and comparison, the XGBoost model (AUC 0.8759) performed the best and was suitable for dealing with regression problems. The model had a high adaptability to landslide data. According to the landslide susceptibility map of the five models, the overall distribution can be observed. The extremely high and high susceptibility areas are distributed in the Funiu Mountain range in the southwest, the Xiaoshan Mountain range in the west, and the Yellow River Basin in the north. These areas have large terrain fluctuations, complicated geological structural environments and frequent human engineering activities. The extremely high and highly prone areas were 12043.3 km2 and 3087.45 km2, accounting for 47.61% and 12.20% of the total area of the study area, respectively. Our study reflects the distribution of landslide susceptibility in western Henan Province, which provides a scientific basis for regional disaster warning, prediction, and resource protection. The study has important practical significance for subsequent landslide disaster management.
2023, 6(3):420-428.
doi: 10.31035/cg2022069
Abstract:
Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated “Snowball Earth” hypothesis and the early evolution of metazoan life. The carbon cycle and redox conditions of the Sturtian-Marinoan non-glacial interval have been subjected to much controversy in the past decades because of the lack of a high-resolution stratigraphic correlation scheme. As one of the typical Sturtian-Marinoan interglacial deposits, the Datangpo Formation was widely distributed in South China with shales continuously deposited. The previous zircon dating data of the Datangpo Formation provide important ages for global constrain of the Sturtian-Marinoan non-glacial interval. Here we present a high-resolution straitigraphic study of the organic carbon isotopes of the Datangpo Formation from a drill core section in northern Guizhou Province. Based on measured episodic δ13Corg perturbations, three positive shifts and three negative excursions are identified. A δ13Corg-based chemostratigraphic correlation scheme is proposed herein that works well for the Datangpo Formation regionally. Meanwhile, the δ13Corg vertical gradients changed dynamically throughout the formation. This discovery implies that a significant ocean circulation overturn might have occurred in the upper Datangpo Formation, coinciding with the potential oxygenation.
Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated “Snowball Earth” hypothesis and the early evolution of metazoan life. The carbon cycle and redox conditions of the Sturtian-Marinoan non-glacial interval have been subjected to much controversy in the past decades because of the lack of a high-resolution stratigraphic correlation scheme. As one of the typical Sturtian-Marinoan interglacial deposits, the Datangpo Formation was widely distributed in South China with shales continuously deposited. The previous zircon dating data of the Datangpo Formation provide important ages for global constrain of the Sturtian-Marinoan non-glacial interval. Here we present a high-resolution straitigraphic study of the organic carbon isotopes of the Datangpo Formation from a drill core section in northern Guizhou Province. Based on measured episodic δ13Corg perturbations, three positive shifts and three negative excursions are identified. A δ13Corg-based chemostratigraphic correlation scheme is proposed herein that works well for the Datangpo Formation regionally. Meanwhile, the δ13Corg vertical gradients changed dynamically throughout the formation. This discovery implies that a significant ocean circulation overturn might have occurred in the upper Datangpo Formation, coinciding with the potential oxygenation.
2023, 6(3):429-442.
doi: 10.31035/cg2022055
Abstract:
The Pearl River Mouth Basin (PRMB) is one of the most petroliferous basins on the northern margin of the South China Sea. Knowledge of the thermal history of the PRMB is significant for understanding its tectonic evolution and for unraveling its poorly studied source-rock maturation history. Our investigations in this study are based on apatite fission-track (AFT) thermochronology analysis of 12 cutting samples from 4 boreholes. Both AFT ages and length data suggested that the PRMB has experienced quite complicated thermal evolution. Thermal history modeling results unraveled four successive events of heating separated by three stages of cooling since the early Middle Eocene. The cooling events occurred approximately in the Late Eocene, early Oligocene, and the Late Miocene, possibly attributed to the Zhuqiong II Event, Nanhai Event, and Dongsha Event, respectively. The erosion amount during the first cooling stage is roughly estimated to be about 455–712 m, with an erosion rate of 0.08–0.12 mm/a. The second erosion-driven cooling is stronger than the first one, with an erosion amount of about 747–814 m and an erosion rate between about 0.13–0.21 mm/a. The erosion amount calculated related to the third cooling event varies from 800 m to 3419 m, which is speculative due to the possible influence of the magmatic activity.
The Pearl River Mouth Basin (PRMB) is one of the most petroliferous basins on the northern margin of the South China Sea. Knowledge of the thermal history of the PRMB is significant for understanding its tectonic evolution and for unraveling its poorly studied source-rock maturation history. Our investigations in this study are based on apatite fission-track (AFT) thermochronology analysis of 12 cutting samples from 4 boreholes. Both AFT ages and length data suggested that the PRMB has experienced quite complicated thermal evolution. Thermal history modeling results unraveled four successive events of heating separated by three stages of cooling since the early Middle Eocene. The cooling events occurred approximately in the Late Eocene, early Oligocene, and the Late Miocene, possibly attributed to the Zhuqiong II Event, Nanhai Event, and Dongsha Event, respectively. The erosion amount during the first cooling stage is roughly estimated to be about 455–712 m, with an erosion rate of 0.08–0.12 mm/a. The second erosion-driven cooling is stronger than the first one, with an erosion amount of about 747–814 m and an erosion rate between about 0.13–0.21 mm/a. The erosion amount calculated related to the third cooling event varies from 800 m to 3419 m, which is speculative due to the possible influence of the magmatic activity.
2023, 6(3):443-454.
doi: 10.31035/cg2022042
Abstract:
The Ordos Basin is the largest continental multi-energy mineral basin in China, which is rich in coal, oil and gas, and uranium resources. The exploitation of mineral resources is closely related to reservoir water. The chemical properties of reservoir water are very important for reservoir evaluation and are significant indicators of the sealing of reservoir oil and gas resources. Therefore, the caprock of the Chang 6 reservoir in the Yanchang Formation was evaluated. The authors tested and analyzed the chemical characteristics of water samples selected from 30 wells in the Chang 6 reservoir of Ansai Oilfield in the Ordos Basin. The results show that the Chang 6 reservoir water in Ansai Oilfield is dominated by calcium-chloride water type with a sodium chloride coefficient of generally less than 0.5. The chloride magnesium coefficients are between 33.7 and 925.5, most of which are greater than 200. The desulfurization coefficients range from 0.21 to 13.4, with an average of 2.227. The carbonate balance coefficients are mainly concentrated below 0.01, with an average of 0.008. The calcium and magnesium coefficients are between 0.08 and 0.003, with an average of 0.01. Combined with the characteristics of the four-corner layout of the reservoir water, the above results show that the graphics are basically consistent. The study indicates that the Chang 6 reservoir in Ansai Oilfield in the Ordos Basin is a favorable block for oil and gas storage with good sealing properties, great preservation conditions of oil and gas, and high pore connectivity.
The Ordos Basin is the largest continental multi-energy mineral basin in China, which is rich in coal, oil and gas, and uranium resources. The exploitation of mineral resources is closely related to reservoir water. The chemical properties of reservoir water are very important for reservoir evaluation and are significant indicators of the sealing of reservoir oil and gas resources. Therefore, the caprock of the Chang 6 reservoir in the Yanchang Formation was evaluated. The authors tested and analyzed the chemical characteristics of water samples selected from 30 wells in the Chang 6 reservoir of Ansai Oilfield in the Ordos Basin. The results show that the Chang 6 reservoir water in Ansai Oilfield is dominated by calcium-chloride water type with a sodium chloride coefficient of generally less than 0.5. The chloride magnesium coefficients are between 33.7 and 925.5, most of which are greater than 200. The desulfurization coefficients range from 0.21 to 13.4, with an average of 2.227. The carbonate balance coefficients are mainly concentrated below 0.01, with an average of 0.008. The calcium and magnesium coefficients are between 0.08 and 0.003, with an average of 0.01. Combined with the characteristics of the four-corner layout of the reservoir water, the above results show that the graphics are basically consistent. The study indicates that the Chang 6 reservoir in Ansai Oilfield in the Ordos Basin is a favorable block for oil and gas storage with good sealing properties, great preservation conditions of oil and gas, and high pore connectivity.
2023, 6(3):455-465.
doi: 10.31035/cg2022057
Abstract:
Conductor and suction anchor are the key equipment providing bearing capacity in the field of deep-water drilling or offshore engineering, which have the advantages of high operation efficiency and short construction period. In order to drill a horizontal well in the shallow hydrate reservoir in the deep water, the suction anchor wellhead assembly is employed to undertake the main vertical bearing capacity in the second round of hydrate trial production project, so as to reduce the conductor running depth and heighten the kick-off point position. However, the deformation law of the deep-water suction anchor wellhead assembly under the moving load of the riser is not clear, and it is necessary to understand the lateral bearing characteristics to guide the design of its structural scheme. Based on 3D solid finite element method, the solid finite element model of the suction anchor wellhead assembly is established. In the model, the seabed soil is divided into seven layers, the contact between the wellhead assembly and the soil is simulated, and the vertical load and bending moment are applied to the wellhead node to simulate the riser movement when working in the deep water. The lateral bearing stability of conventional wellhead assembly and suction anchor wellhead assembly under the influence of wellhead load is discussed. The analysis results show that the bending moment is the main factor affecting the lateral deformation of the wellhead string; the anti-bending performance from increasing the outer conductor diameter is better than that from increasing the conductor wall thickness; for the subsea wellhead, the suction anchor obviously improves the lateral bearing capacity and reduces the lateral deformation. The conduct of the suction anchor wellhead assembly still needs to be lowered to a certain depth that below the maximum disturbed depth to ensure the lateral bearing stability, Thus, a method for the minimum conductor running depth for the suction anchor wellhead assembly is developed. The field implementations show that compared with the first round of hydrate trial production project, the conductor running depth is increased by 9.42 m, and there is no risk of wellhead overturning during the trial production. The method for determining the minimum conductor running depth in this paper is feasible and will still play an important role in the subsequent hydrate exploration and development.
Conductor and suction anchor are the key equipment providing bearing capacity in the field of deep-water drilling or offshore engineering, which have the advantages of high operation efficiency and short construction period. In order to drill a horizontal well in the shallow hydrate reservoir in the deep water, the suction anchor wellhead assembly is employed to undertake the main vertical bearing capacity in the second round of hydrate trial production project, so as to reduce the conductor running depth and heighten the kick-off point position. However, the deformation law of the deep-water suction anchor wellhead assembly under the moving load of the riser is not clear, and it is necessary to understand the lateral bearing characteristics to guide the design of its structural scheme. Based on 3D solid finite element method, the solid finite element model of the suction anchor wellhead assembly is established. In the model, the seabed soil is divided into seven layers, the contact between the wellhead assembly and the soil is simulated, and the vertical load and bending moment are applied to the wellhead node to simulate the riser movement when working in the deep water. The lateral bearing stability of conventional wellhead assembly and suction anchor wellhead assembly under the influence of wellhead load is discussed. The analysis results show that the bending moment is the main factor affecting the lateral deformation of the wellhead string; the anti-bending performance from increasing the outer conductor diameter is better than that from increasing the conductor wall thickness; for the subsea wellhead, the suction anchor obviously improves the lateral bearing capacity and reduces the lateral deformation. The conduct of the suction anchor wellhead assembly still needs to be lowered to a certain depth that below the maximum disturbed depth to ensure the lateral bearing stability, Thus, a method for the minimum conductor running depth for the suction anchor wellhead assembly is developed. The field implementations show that compared with the first round of hydrate trial production project, the conductor running depth is increased by 9.42 m, and there is no risk of wellhead overturning during the trial production. The method for determining the minimum conductor running depth in this paper is feasible and will still play an important role in the subsequent hydrate exploration and development.
2023, 6(3):466-475.
doi: 10.31035/cg2022045
Abstract:
As a prerequisite and a guarantee for safe and efficient natural gas hydrates (NGHs) exploitation, it is imperative to effectively determine the mechanical properties of NGHs reservoirs and clarify the law of the change in the mechanical properties with the dissociation of NGHs during NGHs production tests by depressurization. Based on the development of Japan’s two offshore NGHs production tests in vertical wells, this study innovatively proposed a new subsea communication technology—accurate directional connection using a wet-mate connector. This helps to overcome the technical barrier to the communication between the upper and lower completion of offshore wells. Using this new communication technology, this study explored and designed a mechanical monitoring scheme for lower completion (sand screens). This scheme can be used to monitor the tensile stress and radial compressive stress of sand screens caused by NGHs reservoirs in real time, thus promoting the technical development for the rapid assessment and real-time feedback of the in-situ mechanical response of NGHs reservoirs during offshore NGHs production tests by depressurization.
As a prerequisite and a guarantee for safe and efficient natural gas hydrates (NGHs) exploitation, it is imperative to effectively determine the mechanical properties of NGHs reservoirs and clarify the law of the change in the mechanical properties with the dissociation of NGHs during NGHs production tests by depressurization. Based on the development of Japan’s two offshore NGHs production tests in vertical wells, this study innovatively proposed a new subsea communication technology—accurate directional connection using a wet-mate connector. This helps to overcome the technical barrier to the communication between the upper and lower completion of offshore wells. Using this new communication technology, this study explored and designed a mechanical monitoring scheme for lower completion (sand screens). This scheme can be used to monitor the tensile stress and radial compressive stress of sand screens caused by NGHs reservoirs in real time, thus promoting the technical development for the rapid assessment and real-time feedback of the in-situ mechanical response of NGHs reservoirs during offshore NGHs production tests by depressurization.
2023, 6(3):476-493.
doi: 10.31035/cg2022086
Abstract:
Groundwater with high arsenic (As) content seriously threatens human life and health. Drinking high-As groundwater for a long time will lead to various pathological changes such as skin cancer, liver cancer, and kidney cancer. High-As groundwater has become one of the most serious environmental geological problems in China and even internationally. This paper aims to systematically summarize the sources, migration, distribution, toxicological effects, and treatment techniques of As in natural groundwater in China based on a large number of literature surveys. High-As groundwater in China is mainly distributed in the inland basins in arid and semi-arid environments and the alluvial and lacustrine aquifers in river deltas in humid environments, which are in neutral to weakly alkaline and strongly reducing environments. The content of As in groundwater varies widely, and As(III) is the main form. The main mechanism of the formation of high-As groundwater in China is the reduced dissolution of Fe and Mn oxides under the action of organic matter and primary microorganisms, alkaline environment, intense evaporation and concentration, long-term water-rock interaction, and slow groundwater velocity, which promote the continuous migration and enrichment of As in groundwater. There are obvious differences in the toxicity of different forms of As. The toxic of As(III) is far more than As(V), which is considered to be more toxic than methyl arsenate (MMA) and dimethyl arsenate (DMA). Inorganic As entering the body is metabolized through a combination of methylation (detoxification) and reduction (activation) and catalyzed by a series of methyltransferases and reductases. At present, remediation methods for high-As groundwater mainly include ion exchange technology, membrane filtration technology, biological treatment technology, nanocomposite adsorption technology, electrochemical technology, and so on. All the above remediation methods still have certain limitations, and it is urgent to develop treatment materials and technical means with stronger As removal performance and sustainability. With the joint efforts of scientists and governments of various countries in the future, this worldwide problem of drinking-water As poisoning will be solved as soon as possible. This paper systematically summarizes and discusses the hot research results of natural high-As groundwater, which could provide a reference for the related research of high-As groundwater in China and even the world.
Groundwater with high arsenic (As) content seriously threatens human life and health. Drinking high-As groundwater for a long time will lead to various pathological changes such as skin cancer, liver cancer, and kidney cancer. High-As groundwater has become one of the most serious environmental geological problems in China and even internationally. This paper aims to systematically summarize the sources, migration, distribution, toxicological effects, and treatment techniques of As in natural groundwater in China based on a large number of literature surveys. High-As groundwater in China is mainly distributed in the inland basins in arid and semi-arid environments and the alluvial and lacustrine aquifers in river deltas in humid environments, which are in neutral to weakly alkaline and strongly reducing environments. The content of As in groundwater varies widely, and As(III) is the main form. The main mechanism of the formation of high-As groundwater in China is the reduced dissolution of Fe and Mn oxides under the action of organic matter and primary microorganisms, alkaline environment, intense evaporation and concentration, long-term water-rock interaction, and slow groundwater velocity, which promote the continuous migration and enrichment of As in groundwater. There are obvious differences in the toxicity of different forms of As. The toxic of As(III) is far more than As(V), which is considered to be more toxic than methyl arsenate (MMA) and dimethyl arsenate (DMA). Inorganic As entering the body is metabolized through a combination of methylation (detoxification) and reduction (activation) and catalyzed by a series of methyltransferases and reductases. At present, remediation methods for high-As groundwater mainly include ion exchange technology, membrane filtration technology, biological treatment technology, nanocomposite adsorption technology, electrochemical technology, and so on. All the above remediation methods still have certain limitations, and it is urgent to develop treatment materials and technical means with stronger As removal performance and sustainability. With the joint efforts of scientists and governments of various countries in the future, this worldwide problem of drinking-water As poisoning will be solved as soon as possible. This paper systematically summarizes and discusses the hot research results of natural high-As groundwater, which could provide a reference for the related research of high-As groundwater in China and even the world.
2023, 6(3):494-530.
doi: 10.31035/cg2023039
Abstract:
The Daheishan supergiant porphyry molybdenum deposit (also referred to as the Daheishan deposit) is the second largest molybdenum deposit in Asia and ranks fifth among the top seven molybdenum deposits globally with total molybdenum reserves of 1.65 billion tons, an average molybdenum ore grade of 0.081%, and molybdenum resources of 1.09 million tons. The main ore body is housed in the granodiorite porphyry plutons and their surrounding inequigranular granodiorite plutons, with high-grade ores largely located in the ore-bearing granodiorite porphyries in the middle-upper part of the porphyry plutons. Specifically, it appears as an ore pipe with a large upper part and a small lower part, measuring about 1700 m in length and width, extending for about 500 m vertically, and covering an area of 2.3 km2. Mineralogically, the main ore body consists of molybdenite, chalcopyrite, and sphalerite horizontally from its center outward and exhibits molybdenite, azurite, and pyrite vertically from top to bottom. The primary ore minerals include pyrite and molybdenite, and the secondary ore minerals include sphalerite, chalcopyrite, tetrahedrite, and scheelite, with average grades of molybdenum, copper, sulfur, gallium, and rhenium being 0.081%, 0.033%, 1.67%, 0.001%, and 0.0012%, respectively. The ore-forming fluids of the Daheishan deposit originated as the CO2-H2O-NaCl multiphase magmatic fluid system, rich in CO2 and bearing minor amounts of CH4, N2, and H2S, and later mixed with meteoric precipitation. In various mineralization stages, the ore-forming fluids had homogenization temperatures of > 420°C‒400°C, 360°C‒350°C, 340°C‒230°C, 220°C‒210°C, and 180°C‒160°C and salinities of > 41.05%‒9.8% NaCleqv, 38.16%‒4.48% NaCleqv, 35.78%‒4.49% NaCleqv, 7.43% NaCleqv, and 7.8%‒9.5% NaCleqv, respectively. The mineralization of the Daheishan deposit occurred at 186‒167 Ma. The granites closely related to the mineralization include granodiorites (granodiorite porphyries) and monzogranites (monzogranite porphyries), which were mineralized after magmatic evolution (189‒167 Ma). Moreover, these mineralization-related granites exhibit low initial strontium content and high initial neodymium content, indicating that these granites underwent crust-mantle mixing. The Daheishan deposit formed during the Early-Middle Jurassic, during which basaltic magma underplating induced the lower-crust melting, leading to the formation of magma chambers. After the fractional crystallization of magmas, ore-bearing fluids formed. As the temperature and pressure decreased, the ore-bearing fluids boiled drops while ascending, leading to massive unloading of metal elements. Consequently, brecciated and veinlet-disseminated ore bodies formed.
The Daheishan supergiant porphyry molybdenum deposit (also referred to as the Daheishan deposit) is the second largest molybdenum deposit in Asia and ranks fifth among the top seven molybdenum deposits globally with total molybdenum reserves of 1.65 billion tons, an average molybdenum ore grade of 0.081%, and molybdenum resources of 1.09 million tons. The main ore body is housed in the granodiorite porphyry plutons and their surrounding inequigranular granodiorite plutons, with high-grade ores largely located in the ore-bearing granodiorite porphyries in the middle-upper part of the porphyry plutons. Specifically, it appears as an ore pipe with a large upper part and a small lower part, measuring about 1700 m in length and width, extending for about 500 m vertically, and covering an area of 2.3 km2. Mineralogically, the main ore body consists of molybdenite, chalcopyrite, and sphalerite horizontally from its center outward and exhibits molybdenite, azurite, and pyrite vertically from top to bottom. The primary ore minerals include pyrite and molybdenite, and the secondary ore minerals include sphalerite, chalcopyrite, tetrahedrite, and scheelite, with average grades of molybdenum, copper, sulfur, gallium, and rhenium being 0.081%, 0.033%, 1.67%, 0.001%, and 0.0012%, respectively. The ore-forming fluids of the Daheishan deposit originated as the CO2-H2O-NaCl multiphase magmatic fluid system, rich in CO2 and bearing minor amounts of CH4, N2, and H2S, and later mixed with meteoric precipitation. In various mineralization stages, the ore-forming fluids had homogenization temperatures of > 420°C‒400°C, 360°C‒350°C, 340°C‒230°C, 220°C‒210°C, and 180°C‒160°C and salinities of > 41.05%‒9.8% NaCleqv, 38.16%‒4.48% NaCleqv, 35.78%‒4.49% NaCleqv, 7.43% NaCleqv, and 7.8%‒9.5% NaCleqv, respectively. The mineralization of the Daheishan deposit occurred at 186‒167 Ma. The granites closely related to the mineralization include granodiorites (granodiorite porphyries) and monzogranites (monzogranite porphyries), which were mineralized after magmatic evolution (189‒167 Ma). Moreover, these mineralization-related granites exhibit low initial strontium content and high initial neodymium content, indicating that these granites underwent crust-mantle mixing. The Daheishan deposit formed during the Early-Middle Jurassic, during which basaltic magma underplating induced the lower-crust melting, leading to the formation of magma chambers. After the fractional crystallization of magmas, ore-bearing fluids formed. As the temperature and pressure decreased, the ore-bearing fluids boiled drops while ascending, leading to massive unloading of metal elements. Consequently, brecciated and veinlet-disseminated ore bodies formed.
2023, 6(3):536-540.
doi: 10.31035/cg2023051
Abstract:
2023, 6(3):1-2.
Abstract:
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