The source of ore\|forming materials has long been a controversial focus both in metallogenic theory and in ore\|searching practice. This study deals with the helium and argon isotopic characteristics of pyrites from ...The source of ore\|forming materials has long been a controversial focus both in metallogenic theory and in ore\|searching practice. This study deals with the helium and argon isotopic characteristics of pyrites from 11 gold deposits and some country rocks in the gold mineralization\|concentrated areas within the three mantle\|branch structures in the region of North Hebei Province. It is indicated that \{\}\+3He/\+4He ratios in the gold deposits are within the range of \{0.93×10\+\{-6\}\}-\{7.3×10\+\{-6\}\}, with an average of \{3.55\} ×10\+\{-6\}; R/Ra=\{0.66\}-\{4.93\}, averaging \{2.53\}; \{\{\}\+\{40\}Ar/\+\{39\}Ar\} ratios vary between 426 and 2073, with the average value of \{\}\+\{40\}Ar being \{8.32\}; and the average of \{\}\+4He/\{\}\+\{40\}Ar ratios is 2.17. \{\}\+3He/ \{\}\+4He ratios in gneiss and granite in the periphery of the mining district are within the range of \{0.001×10\+\{-6\}\}-\{0.55×10\+\{-6\}\}, reflecting significant differences in their sources. \{\}\+3He and \{\}\+4He fall near the mantle, as is shown in the He concentration diagram. Studies have shown that the ore\|forming materials in this region should come from the deep interior of the Earth. With the multi\|stage evolution of mantle plume, ore\|forming fluids in the deep interior were moving upwards to shallow levels (crust). Under such circumstances, there would be inevitably occur crust/mantle fluid mixing, so their noble gas isotopic characteristics are intermediate between the mantle and the crust.展开更多
Land degradation is one of the serious environmental problems that can lead to poverty, and is especially prominent in eco-fragile areas in developing countries and increases the risk of environmental safety. North He...Land degradation is one of the serious environmental problems that can lead to poverty, and is especially prominent in eco-fragile areas in developing countries and increases the risk of environmental safety. North Hebei Province belongs to an ecologically fragile region in North China, which has great impact on the eco-safety of Beijing and Tianjin. Using Landsat TM data and GIS, this paper evaluates land degradation in North Hebei province of China from the the 1960′s to 1987 and 2000. Land use/cover change pattern from 1987 to 2000, its regional difference and forest change characteristics will also be analyzed; soil erosion intensity and arable land suitability were also evaluated. Results revealed that land use/cover pattern in this study area did not change greatly from 1987 to 2000. The structure and function of regional land ecosystem was at a level of local improvement and integral deterioration. Land above medium soil erosion intensity reached 21 percent, which was also the area with a serious soil erosion and land degradation problem. Soil erosion and land degradation intensity of grassland was the biggest. For the present arable land, the proportion of high suitability was 13 percent.展开更多
Experiments were carried out in 1994 - 1998 to study crop rotation and its effects on crop water consumption characteristics of field with sandy chestnut soil in the Plateau of north Hebei Province. Five crops includi...Experiments were carried out in 1994 - 1998 to study crop rotation and its effects on crop water consumption characteristics of field with sandy chestnut soil in the Plateau of north Hebei Province. Five crops including spring wheat, oat, pea, flax and potato were examined. There was little difference in field water consumption among the crops during the growing season. WUE varied significantly in a range of 1. 347 -11.177kg · ha-1 · mm-1 among crops and 11.44% - 46.66% among previous crops. It was pointed out that the land equivalent ratio (LER) can be used as an index to evaluate the biological effects of crop rotation comprehensively. The 2-4 year crop rotation patterns with higher LER were estimated in the paper.展开更多
During the past decade,generations of Precambrian mafic dykes/sills have been investigated and revealed in the North China Craton(NCC).Researchers identified more than 20 episodes of Precambrian dyke swarms,
Drought monitoring is the base for drought coping and adaptation. Xingtai is located in North China＇s key winter wheat production areas where drought is severe and frequent. The rainfall during winter wheat growing s...Drought monitoring is the base for drought coping and adaptation. Xingtai is located in North China＇s key winter wheat production areas where drought is severe and frequent. The rainfall during winter wheat growing season is just about 1/3 of total demand. Xingtai has typical mountainous, hilly and plain agricultural zones, compound rain-fed and irrigated farming patterns. The winter wheat irrigation has heavily depended on overdraw of groundwater in recent decades. In the study, the MODIS （Moderate-Resolution Imaging Spectroradiometer） images taken at the key winter wheat growing season （Mar. to May） in normal rainfall year （2006） were selected, extracted NDVI （Normalized Difference Vegetation Index） and LST （Land Surface Temperature） data, calculated TVDI （Temperature and Vegetation Drought Index）, classified and mapped winter wheat drought intensity. Further, based on TVDI, a CDRA （Comprehensive Drought Risk Assessment） model for winter wheat drought disaster risk assessment was constructed and zoning was made. Verified by winter wheat yield, the risk zoning by CDRA is consistent with actual crop failure space. This method can be used in drought risk management.展开更多
以冀北康保芦家营巨斑状花岗岩为对象,进行了岩相学、地球化学、锆石U-Pb年代学研究,探讨其构造属性、形成时代,进而为华北克拉通北缘1.3~1.2 Ga B.P.伸展-裂解事件研究提供新的证据。巨斑状花岗岩体主要出露在康保芦家营、小英图及永...以冀北康保芦家营巨斑状花岗岩为对象,进行了岩相学、地球化学、锆石U-Pb年代学研究,探讨其构造属性、形成时代,进而为华北克拉通北缘1.3~1.2 Ga B.P.伸展-裂解事件研究提供新的证据。巨斑状花岗岩体主要出露在康保芦家营、小英图及永德堂一带,呈北东-南西向展布,侵位于中元古代化德群之中,而后又被晚古生代-中生代花岗岩体所侵入。花岗岩体的岩性单一,为片麻状-弱片麻状似斑状黑云二长花岗岩,以含有许多不等量且个体粗大(较大者可达5~10 cm,多数在3~5 cm)、呈板柱状或眼球状产出的微斜长石巨斑(可有少量斜长石巨斑)及黑云母成团分布为特征。巨斑状花岗岩具有铝质A型花岗岩(A 2亚类)的地球化学属性,形成于陆缘裂谷(裂陷槽)的构造环境,可能属于中-上地壳钙碱性花岗质岩石部分熔融、冷凝结晶形成的板内花岗岩。巨斑状花岗岩的锆石LA-ICP-MS U-Pb年龄为(1235±7.9)Ma,表明其形成于中元古代晚期,应该是华北克拉通北缘1.3~1.2 Ga B.P.伸展-裂解事件的地质记录,可与华北克拉通广泛存在的1.3~1.2 Ga B.P.基性岩墙群相对应。从全球范围内广泛存在的1.3~1.2 Ga B.P.伸展-裂解事件来看,华北克拉通北缘中段1.3~1.2 Ga B.P.伸展-裂解事件应与哥伦比亚超大陆的最后一次裂解有关,是华北克拉通对哥伦比亚超大陆晚期裂解事件的响应。展开更多
文摘The source of ore\|forming materials has long been a controversial focus both in metallogenic theory and in ore\|searching practice. This study deals with the helium and argon isotopic characteristics of pyrites from 11 gold deposits and some country rocks in the gold mineralization\|concentrated areas within the three mantle\|branch structures in the region of North Hebei Province. It is indicated that \{\}\+3He/\+4He ratios in the gold deposits are within the range of \{0.93×10\+\{-6\}\}-\{7.3×10\+\{-6\}\}, with an average of \{3.55\} ×10\+\{-6\}; R/Ra=\{0.66\}-\{4.93\}, averaging \{2.53\}; \{\{\}\+\{40\}Ar/\+\{39\}Ar\} ratios vary between 426 and 2073, with the average value of \{\}\+\{40\}Ar being \{8.32\}; and the average of \{\}\+4He/\{\}\+\{40\}Ar ratios is 2.17. \{\}\+3He/ \{\}\+4He ratios in gneiss and granite in the periphery of the mining district are within the range of \{0.001×10\+\{-6\}\}-\{0.55×10\+\{-6\}\}, reflecting significant differences in their sources. \{\}\+3He and \{\}\+4He fall near the mantle, as is shown in the He concentration diagram. Studies have shown that the ore\|forming materials in this region should come from the deep interior of the Earth. With the multi\|stage evolution of mantle plume, ore\|forming fluids in the deep interior were moving upwards to shallow levels (crust). Under such circumstances, there would be inevitably occur crust/mantle fluid mixing, so their noble gas isotopic characteristics are intermediate between the mantle and the crust.
基金The authors would like to greatly thank the National Natural Science Foundation of China(No.40171001 and No.40571117)the grant of the Knowledge Innovation Program of the Chinese Academy of Sciences(approved # KZCX3-SW-338)National High Technology Research and Development Program of China(No:2003AA131170)which founded this research.
文摘Land degradation is one of the serious environmental problems that can lead to poverty, and is especially prominent in eco-fragile areas in developing countries and increases the risk of environmental safety. North Hebei Province belongs to an ecologically fragile region in North China, which has great impact on the eco-safety of Beijing and Tianjin. Using Landsat TM data and GIS, this paper evaluates land degradation in North Hebei province of China from the the 1960′s to 1987 and 2000. Land use/cover change pattern from 1987 to 2000, its regional difference and forest change characteristics will also be analyzed; soil erosion intensity and arable land suitability were also evaluated. Results revealed that land use/cover pattern in this study area did not change greatly from 1987 to 2000. The structure and function of regional land ecosystem was at a level of local improvement and integral deterioration. Land above medium soil erosion intensity reached 21 percent, which was also the area with a serious soil erosion and land degradation problem. Soil erosion and land degradation intensity of grassland was the biggest. For the present arable land, the proportion of high suitability was 13 percent.
文摘Experiments were carried out in 1994 - 1998 to study crop rotation and its effects on crop water consumption characteristics of field with sandy chestnut soil in the Plateau of north Hebei Province. Five crops including spring wheat, oat, pea, flax and potato were examined. There was little difference in field water consumption among the crops during the growing season. WUE varied significantly in a range of 1. 347 -11.177kg · ha-1 · mm-1 among crops and 11.44% - 46.66% among previous crops. It was pointed out that the land equivalent ratio (LER) can be used as an index to evaluate the biological effects of crop rotation comprehensively. The 2-4 year crop rotation patterns with higher LER were estimated in the paper.
基金supported by the Major State Basic Research Development Program of China (973 Program No: 2012CB416601)+1 种基金the National Natural Science Foundation of China (No: 41322018) projectsthe National High-Level Talents Special Support Plan
文摘During the past decade,generations of Precambrian mafic dykes/sills have been investigated and revealed in the North China Craton(NCC).Researchers identified more than 20 episodes of Precambrian dyke swarms,
基金The study was supported by the National Natural Science Foundation of China [No.46171501 ].
文摘Drought monitoring is the base for drought coping and adaptation. Xingtai is located in North China＇s key winter wheat production areas where drought is severe and frequent. The rainfall during winter wheat growing season is just about 1/3 of total demand. Xingtai has typical mountainous, hilly and plain agricultural zones, compound rain-fed and irrigated farming patterns. The winter wheat irrigation has heavily depended on overdraw of groundwater in recent decades. In the study, the MODIS （Moderate-Resolution Imaging Spectroradiometer） images taken at the key winter wheat growing season （Mar. to May） in normal rainfall year （2006） were selected, extracted NDVI （Normalized Difference Vegetation Index） and LST （Land Surface Temperature） data, calculated TVDI （Temperature and Vegetation Drought Index）, classified and mapped winter wheat drought intensity. Further, based on TVDI, a CDRA （Comprehensive Drought Risk Assessment） model for winter wheat drought disaster risk assessment was constructed and zoning was made. Verified by winter wheat yield, the risk zoning by CDRA is consistent with actual crop failure space. This method can be used in drought risk management.
文摘以冀北康保芦家营巨斑状花岗岩为对象,进行了岩相学、地球化学、锆石U-Pb年代学研究,探讨其构造属性、形成时代,进而为华北克拉通北缘1.3~1.2 Ga B.P.伸展-裂解事件研究提供新的证据。巨斑状花岗岩体主要出露在康保芦家营、小英图及永德堂一带,呈北东-南西向展布,侵位于中元古代化德群之中,而后又被晚古生代-中生代花岗岩体所侵入。花岗岩体的岩性单一,为片麻状-弱片麻状似斑状黑云二长花岗岩,以含有许多不等量且个体粗大(较大者可达5~10 cm,多数在3~5 cm)、呈板柱状或眼球状产出的微斜长石巨斑(可有少量斜长石巨斑)及黑云母成团分布为特征。巨斑状花岗岩具有铝质A型花岗岩(A 2亚类)的地球化学属性,形成于陆缘裂谷(裂陷槽)的构造环境,可能属于中-上地壳钙碱性花岗质岩石部分熔融、冷凝结晶形成的板内花岗岩。巨斑状花岗岩的锆石LA-ICP-MS U-Pb年龄为(1235±7.9)Ma,表明其形成于中元古代晚期,应该是华北克拉通北缘1.3~1.2 Ga B.P.伸展-裂解事件的地质记录,可与华北克拉通广泛存在的1.3~1.2 Ga B.P.基性岩墙群相对应。从全球范围内广泛存在的1.3~1.2 Ga B.P.伸展-裂解事件来看,华北克拉通北缘中段1.3~1.2 Ga B.P.伸展-裂解事件应与哥伦比亚超大陆的最后一次裂解有关,是华北克拉通对哥伦比亚超大陆晚期裂解事件的响应。
