In this paper, the Finite Volume Coastal Ocean Model （FVCOM） was employed and configured for 3 dimensional numerical simulations of tide and tidal current based on the field observations in Zhanjiang Bay. The model...In this paper, the Finite Volume Coastal Ocean Model （FVCOM） was employed and configured for 3 dimensional numerical simulations of tide and tidal current based on the field observations in Zhanjiang Bay. The model＇s results agree well with the field observed data. Based on the well validated model, the hydrodynamic fields of zhanjiang bay area were calculated both before the Donghai Dam constructing and after that. Compared the tidal level, current field, tidal capacity and water exchange ratio before the construction of Dohai dam with those after construction of the dam, we analyzed and get some conclusions of effects of Donghai Dam on Hydrodynamic environment of the Zhanjiang Bay.展开更多
The content and distribution of acid-volatile sulfide （AVS） and simultaneously extracted metals （SEM） （Cr Cu, Zn, Cd and Pb） were studied in surface sediments collected from the tidal fiat of Donghai Island, Zha...The content and distribution of acid-volatile sulfide （AVS） and simultaneously extracted metals （SEM） （Cr Cu, Zn, Cd and Pb） were studied in surface sediments collected from the tidal fiat of Donghai Island, Zhanjiang. The results indicated that for most stations, the AVS concentration was higher in summer with the average of 0.449 μmol/g than that in winter with the average of 1.816 μmol/g. The AVS contents were higher in southern and northern areas and lower in western and eastern areas. The average content of ∑SEM was between 0.56 μmol/g and 4.60 μmol/g in summer and between 0.65μmol/g and 2.21 μmol/g in winter. The concentration change of single metal was Zn〉Cr〉Pb〉Cu〉Cd for most stations. The content percentage in ∑ SEM was below 1% for Cd and over 70% for Zn. SEMZn was the key pattern to control the distribution of T. SEM due to its high concentration percentage. Based on the assessment methods of （∑SEM/AVS） with （∑ SEM-AVS） and thresholds for metal toxicity to benthic organism, most values of （∑ SEM-AVS） in intertidal flats of Donghai Island were between 0 and 5. The most toxicity region was in Tongminghai area located in the west tidal zone of Donghai Island, and the most toxicity metal was zinc in Tongminghai area in summer. The land-based pollution and the environmental parameters such as sunlight, atmosphere temperature and hydrodynamic characteristics were the main affecting factors on the content level and distribution characteristics of AVS and SEM in intertidal sediments of Donghai Island.展开更多
Recent investigations reveal that the ultrahigh-pressure metamorphic (UHPM) rocks in the Donghai region of East China underwent ductile and transitional ductile-brittle structural events during their exhumation. The e...Recent investigations reveal that the ultrahigh-pressure metamorphic (UHPM) rocks in the Donghai region of East China underwent ductile and transitional ductile-brittle structural events during their exhumation. The earlier ductile deformation took place under the condition of amphibolite facies and the later transitional ductile-brittle deformation under the condition of greenschist facies. The hanging walls moved southeastward during both of these two events. The 40Ar/39Ar dating of muscovites from muscovite-plagioclase schists in the Haizhou phosphorous mine, which are structurally overlain by UHPM rocks, yields a plateau age of 218.0±2.9 Ma and isochron age of 219.8Ma, indicating that the earlier event of the ampibolite-facies deformation probably took place about 220 Ma ago. The 40Ar/39Ar dating of oriented amphiboles parallel to the movement direction of the hanging wall on a decollement plane yields a plateau age of 213.1±0.3 Ma and isochron age of 213.4±4.1 Ma, probably representing the age of the later event. The dating of pegmatitic biotites and K-feldspars near the decollement plane from the eastern Fangshan area yield plateau ages of 203.4±0.3 Ma, 203.6±0.4 Ma and 204.8±2.2 Ma, and isochron ages of 204.0±2.0 Ma, 200.6±3.1 Ma and 204.0±5.0 Ma, respectively, implying that the rocks in the studied area had not been cooled down to closing temperature of the dated biotites and K-feldspars until the beginning of the Jurassic (about 204 Ma). The integration of these data with previous chronological ages on the ultrahigh-pressure metamorphism lead to a new inference on the exhumation of the UHPM rocks. The UHPM rocks in the area were exhumed at the rate of 3-4 km/Ma from the mantle (about 80-100 km below the earth's surface at about 240 Ma) to the lower crust (at the depth of about 20-30km at 220 Ma), and at the rate of 1-2 km/Ma to the middle crust (at the depth of about 15 km at 213 Ma), and then at the rate of less than 1 km/Ma to the upper crust about 10 km deep at about 204 Ma.展开更多
In the gneisses from the drillhole ZK2304 of the Donghai area, there have been preserved high- and ultrahigh-pressure metamorphic mineral assemblages, a series of complicated retrogressive textures and relevant metamo...In the gneisses from the drillhole ZK2304 of the Donghai area, there have been preserved high- and ultrahigh-pressure metamorphic mineral assemblages, a series of complicated retrogressive textures and relevant metamorphic reactions. In addition to garnet, jadeititic-clinopyroxene and rutile, other peak stage (M2) minerals in some gneisses include phengite, aragonite and coesite or quartz pseudomorphs after coesite. The typical peak-stage mineral assemblages in gneisses are characterized by garnet + jadeitic-clinopyroxene + rutile + coesite, garnet + jadeitic-clinopyroxene + phengite + rutile ± coesite and garnet + jadeitic-clinopyroxene + aragonite + rutile ± coesite. The grossular content (Gro) in garnet is high and may reach 50. 1 mol%. The SiO2 content of phengite ranges from 54.37% to 54.84% with 3.54-3.57 p.f.u. Quartz pseudomorphs after coesite occur as inclusions in garnet.The gneisses of the Donghai area have been subjected to multistage recrystallization and exhibit a closewise P-T evolutional path characterized by the near-isothermal decompression. The inclusion assemblage (Hb+Ep+Bi+Pl+Qz) within garnet and other minerals has recorded a pre-peak stage (Mi) epidote amphibole fades metamorphic event. High- and ultrahigh-pressure peak metamorphism (M2) took place at T=750-860℃ and P>2.7 GPa. The symplectitic assemblages after garnet, jadeitic-clinopyroxene and rutile imply a near-isothermal decompression metamorphism (M3, M4) during the rapid exhumation. Several lines of evidence of petrography and metamorphic reactions indicate that both gneisses and eclogites have experienced ultrahigh-pressure metamorphism in the Donghai area. This research may be of great significance for an in-depth study of the metamorphism and tectonic evolution in the Su-Lu ultrahigh-pressure metamorphic belt.展开更多
Study of micro-area chemical compositions indicates that phengite in albite gneiss from hole ZK2304 of the Donghai region has evident compositional zoning. SiO2 and tetrahedrally coordinated Si contents decrease, and ...Study of micro-area chemical compositions indicates that phengite in albite gneiss from hole ZK2304 of the Donghai region has evident compositional zoning. SiO2 and tetrahedrally coordinated Si contents decrease, and Al2O3, AlIVand AlVIcontents increase gradually from core to rim. However, K2O, MgO and FeO contents basically remain unchanged from core to rim. According to P-T estimates obtained from geothermometers and barometers, combined with previous experimental data, the core belt (micro-area I) of phengite was formed at T=637–672°C and P=1.55–1.73 GPa, and the transitional belt (micro-area II) of the phengite were formed at T=594–654°C and P=1.35–1.45 GPa. Towards the rim belt (micro-area III), the temperature decreased slightly, but the pressure decreased rapidly with T=542–630°C and P=1.12–1.19 GPa. The P-T evolution path recorded by the compositional zoning of phengite is characterized by significant near-isothermal decompression, revealing that the gneiss has undergone high-pressure-ultrahigh-pressure metamorphism. The compositional zoning of the phengite in the albite gneiss may have formed in the geodynamic process of rapid exhumation in the Sulu ultrahigh-pressure metamorphic belt.展开更多
Classical statistics,Inverse Distance Weighted and Hakasnson potential ecological index were used to study the distribution characteristics of 8 kinds of heavy metals( Cr,Ni,Cu,Zn,As,Cd,Pb and Hg) as well as their pot...Classical statistics,Inverse Distance Weighted and Hakasnson potential ecological index were used to study the distribution characteristics of 8 kinds of heavy metals( Cr,Ni,Cu,Zn,As,Cd,Pb and Hg) as well as their potential ecological risks in the topsoil( 0-20 cm) of cultivated land in Donghai County,a typical agricultural area along the Southeast Coast of China.The results showed that the average content of heavy metals in the cultivated soil of Donghai County was not over the risk screening values set in the Environmental Quality Standard for Soils.However,it was worth noting that in some of the sampling points,the content of Cr exceeded the risk screening value,and the standard exceeding points accounted for 24.74% of the total.In addition,the average content of Cr,Ni,As,Cd,Pb and Hg exceeded the soil background values of Jiangsu Province,and values for Cd,Cr and Pb were more than 1.5 times of the soil background value of Jiangsu Province.The heavy metals were at the medium integrated potential ecological risk level,and the potential ecological risk indices were high in the east and low in the west,and distributed in interlaced island shape.The potential ecological risk indices of the plains in the east were higher than those of the central gentle slope area and the western hillock area.The potential ecological risk was at a high level in Niushan Town which was situated the county center and in some regions with high urbanization levels.展开更多
文摘In this paper, the Finite Volume Coastal Ocean Model （FVCOM） was employed and configured for 3 dimensional numerical simulations of tide and tidal current based on the field observations in Zhanjiang Bay. The model＇s results agree well with the field observed data. Based on the well validated model, the hydrodynamic fields of zhanjiang bay area were calculated both before the Donghai Dam constructing and after that. Compared the tidal level, current field, tidal capacity and water exchange ratio before the construction of Dohai dam with those after construction of the dam, we analyzed and get some conclusions of effects of Donghai Dam on Hydrodynamic environment of the Zhanjiang Bay.
基金supported by Marine Public Industry Research of Oceanic Administration, China (2013418038-6)
文摘The content and distribution of acid-volatile sulfide （AVS） and simultaneously extracted metals （SEM） （Cr Cu, Zn, Cd and Pb） were studied in surface sediments collected from the tidal fiat of Donghai Island, Zhanjiang. The results indicated that for most stations, the AVS concentration was higher in summer with the average of 0.449 μmol/g than that in winter with the average of 1.816 μmol/g. The AVS contents were higher in southern and northern areas and lower in western and eastern areas. The average content of ∑SEM was between 0.56 μmol/g and 4.60 μmol/g in summer and between 0.65μmol/g and 2.21 μmol/g in winter. The concentration change of single metal was Zn〉Cr〉Pb〉Cu〉Cd for most stations. The content percentage in ∑ SEM was below 1% for Cd and over 70% for Zn. SEMZn was the key pattern to control the distribution of T. SEM due to its high concentration percentage. Based on the assessment methods of （∑SEM/AVS） with （∑ SEM-AVS） and thresholds for metal toxicity to benthic organism, most values of （∑ SEM-AVS） in intertidal flats of Donghai Island were between 0 and 5. The most toxicity region was in Tongminghai area located in the west tidal zone of Donghai Island, and the most toxicity metal was zinc in Tongminghai area in summer. The land-based pollution and the environmental parameters such as sunlight, atmosphere temperature and hydrodynamic characteristics were the main affecting factors on the content level and distribution characteristics of AVS and SEM in intertidal sediments of Donghai Island.
文摘Recent investigations reveal that the ultrahigh-pressure metamorphic (UHPM) rocks in the Donghai region of East China underwent ductile and transitional ductile-brittle structural events during their exhumation. The earlier ductile deformation took place under the condition of amphibolite facies and the later transitional ductile-brittle deformation under the condition of greenschist facies. The hanging walls moved southeastward during both of these two events. The 40Ar/39Ar dating of muscovites from muscovite-plagioclase schists in the Haizhou phosphorous mine, which are structurally overlain by UHPM rocks, yields a plateau age of 218.0±2.9 Ma and isochron age of 219.8Ma, indicating that the earlier event of the ampibolite-facies deformation probably took place about 220 Ma ago. The 40Ar/39Ar dating of oriented amphiboles parallel to the movement direction of the hanging wall on a decollement plane yields a plateau age of 213.1±0.3 Ma and isochron age of 213.4±4.1 Ma, probably representing the age of the later event. The dating of pegmatitic biotites and K-feldspars near the decollement plane from the eastern Fangshan area yield plateau ages of 203.4±0.3 Ma, 203.6±0.4 Ma and 204.8±2.2 Ma, and isochron ages of 204.0±2.0 Ma, 200.6±3.1 Ma and 204.0±5.0 Ma, respectively, implying that the rocks in the studied area had not been cooled down to closing temperature of the dated biotites and K-feldspars until the beginning of the Jurassic (about 204 Ma). The integration of these data with previous chronological ages on the ultrahigh-pressure metamorphism lead to a new inference on the exhumation of the UHPM rocks. The UHPM rocks in the area were exhumed at the rate of 3-4 km/Ma from the mantle (about 80-100 km below the earth's surface at about 240 Ma) to the lower crust (at the depth of about 20-30km at 220 Ma), and at the rate of 1-2 km/Ma to the middle crust (at the depth of about 15 km at 213 Ma), and then at the rate of less than 1 km/Ma to the upper crust about 10 km deep at about 204 Ma.
文摘In the gneisses from the drillhole ZK2304 of the Donghai area, there have been preserved high- and ultrahigh-pressure metamorphic mineral assemblages, a series of complicated retrogressive textures and relevant metamorphic reactions. In addition to garnet, jadeititic-clinopyroxene and rutile, other peak stage (M2) minerals in some gneisses include phengite, aragonite and coesite or quartz pseudomorphs after coesite. The typical peak-stage mineral assemblages in gneisses are characterized by garnet + jadeitic-clinopyroxene + rutile + coesite, garnet + jadeitic-clinopyroxene + phengite + rutile ± coesite and garnet + jadeitic-clinopyroxene + aragonite + rutile ± coesite. The grossular content (Gro) in garnet is high and may reach 50. 1 mol%. The SiO2 content of phengite ranges from 54.37% to 54.84% with 3.54-3.57 p.f.u. Quartz pseudomorphs after coesite occur as inclusions in garnet.The gneisses of the Donghai area have been subjected to multistage recrystallization and exhibit a closewise P-T evolutional path characterized by the near-isothermal decompression. The inclusion assemblage (Hb+Ep+Bi+Pl+Qz) within garnet and other minerals has recorded a pre-peak stage (Mi) epidote amphibole fades metamorphic event. High- and ultrahigh-pressure peak metamorphism (M2) took place at T=750-860℃ and P>2.7 GPa. The symplectitic assemblages after garnet, jadeitic-clinopyroxene and rutile imply a near-isothermal decompression metamorphism (M3, M4) during the rapid exhumation. Several lines of evidence of petrography and metamorphic reactions indicate that both gneisses and eclogites have experienced ultrahigh-pressure metamorphism in the Donghai area. This research may be of great significance for an in-depth study of the metamorphism and tectonic evolution in the Su-Lu ultrahigh-pressure metamorphic belt.
基金This study was supported by the Ministry of Land and Resources of China Projects“1:250000 Regional Geological Surveyofthe Lianyugang Sheet (150C002004) of P.R.China""Geological Research for Selecting a Drillhole in the Donghai TargetArea of the Chinese Continental Scientific Drilling Programme”.
文摘Study of micro-area chemical compositions indicates that phengite in albite gneiss from hole ZK2304 of the Donghai region has evident compositional zoning. SiO2 and tetrahedrally coordinated Si contents decrease, and Al2O3, AlIVand AlVIcontents increase gradually from core to rim. However, K2O, MgO and FeO contents basically remain unchanged from core to rim. According to P-T estimates obtained from geothermometers and barometers, combined with previous experimental data, the core belt (micro-area I) of phengite was formed at T=637–672°C and P=1.55–1.73 GPa, and the transitional belt (micro-area II) of the phengite were formed at T=594–654°C and P=1.35–1.45 GPa. Towards the rim belt (micro-area III), the temperature decreased slightly, but the pressure decreased rapidly with T=542–630°C and P=1.12–1.19 GPa. The P-T evolution path recorded by the compositional zoning of phengite is characterized by significant near-isothermal decompression, revealing that the gneiss has undergone high-pressure-ultrahigh-pressure metamorphism. The compositional zoning of the phengite in the albite gneiss may have formed in the geodynamic process of rapid exhumation in the Sulu ultrahigh-pressure metamorphic belt.
文摘Classical statistics,Inverse Distance Weighted and Hakasnson potential ecological index were used to study the distribution characteristics of 8 kinds of heavy metals( Cr,Ni,Cu,Zn,As,Cd,Pb and Hg) as well as their potential ecological risks in the topsoil( 0-20 cm) of cultivated land in Donghai County,a typical agricultural area along the Southeast Coast of China.The results showed that the average content of heavy metals in the cultivated soil of Donghai County was not over the risk screening values set in the Environmental Quality Standard for Soils.However,it was worth noting that in some of the sampling points,the content of Cr exceeded the risk screening value,and the standard exceeding points accounted for 24.74% of the total.In addition,the average content of Cr,Ni,As,Cd,Pb and Hg exceeded the soil background values of Jiangsu Province,and values for Cd,Cr and Pb were more than 1.5 times of the soil background value of Jiangsu Province.The heavy metals were at the medium integrated potential ecological risk level,and the potential ecological risk indices were high in the east and low in the west,and distributed in interlaced island shape.The potential ecological risk indices of the plains in the east were higher than those of the central gentle slope area and the western hillock area.The potential ecological risk was at a high level in Niushan Town which was situated the county center and in some regions with high urbanization levels.
