首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 687 毫秒
1.
2.
For understanding the Mesozoic tectonics of Yanshan (燕山 ) belt, the authors took geological mapping in the belt. A large-scale thrust structure was identified in Yonganpu (永安堡) area. in the western part of Suizhong (绥中 ) County, Liaoning (辽宁 ) Province during our recent mapping in the Yanshan belt. The hanging wall of the thrust was composed of Archean gneiss and the overlying Early Cretaceous Zhangjiakou (张家口 ) Formation; meanwhile, the strongly ductile deformed volcanic rocks of Zhangjiakou Formation comprised the footwall in Yong'anpu tectonic window. This discovery indicates the existence of strongly contractional deformation in the Yanshan belt after the eruption of Early Cretaceous Zhangjiakou volcanic rocks. On the basis of mapping and research, it is concluded that the published official geological maps have failed to identify the major structural features of the Yanshan belt.  相似文献   

3.
Ground water from Mt. Fuji, located on the border of Yamanashi and Shizuoka prefectures, has relatively high concentrations of trace element vanadium. The concentration is about 50 μg/L around the mountain, and about 1 μg/L in other areas. The vanadium comes from the lava of the mountain. The water is utilized as a source of tap water around the mountain, and habitants are drinking and using the water for cooking. Recent reports by some researchers suggest health beneficial effects of drinking the water; drinking such water can lower blood glucose level in diabetic patients, and improve insulin-resistant status in healthy women. However, the concentration of vanadium in the ground water is too low as compared with the apparently effective concentration (100000 μg/L) in preceding reports. Furthermore, the effects of vanadium in the water on public health are not elucidated. In the present study the regional concentrations of vanadium in ground waters were investigated in Yamanashi prefecture, and standardized mortality rates (SMR) are compared preliminary with vanadium data in order to investigate the effect epidemiologically. SMR data were provided by Health, Labor and Welfare Ministry. We used the summarized SMR from 1998 to 2002. The data contain SMRs from total causes; total malignant neoplasm; stomach cancer; colorectal cancer; liver and intrahepatic bile duct cancer; trachea bronchus and lung cancer; all heart diseases; acute myocardial infarction; and cerebrovascular disease. There are eight secondary medical districts in Yamanashi prefecture, and one of them, Fuji-hokuroku (No.7), corresponds to high-vanadium area. No SMIL except SMR from cerebrovascular disease in female, was lower in the district No.7 than other eight districts. On the other hand, SMRs from all heart diseases and from acute myocardial infarction of both male and female in the district No.7 were highest among the districts. SMR from all causes in male of No.7 was also highest among the districts.  相似文献   

4.
This chapter provides a lithostratigraphic correlation and the present knowledge of the depositional history of the Tertiary succession of the Scandinavian countries. The succession records an initial phase of carbonate deposition in the early Paleocene. This was succeeded by deposition of deep marine clays with intercalation of sand-rich mass-flow deposits during most of the Paleocene and Eocene. Volcanic activity in the North Atlantic was extensive at the transition from the Paleocene to the Eocene resulting in widespread sedimentation of ash-rich layers in the North Sea area. During the Oligocene, the first prograding deltaic complex developed, sourced from the Fennoscandian Shield. Late Oligocene-Early Miocene inversion and uplift of Norway and the Shetland Platform resulted in major progradation of coastal and delta plain systems. At the end of the Tertiary most of the North Sea basin was filled and the Fennoscandian Shield was flanked to the west by a broad, coalesced coastal plain.  相似文献   

5.
Through systematic sampling and analysis of water and soil in the planning area of Langfang City, employing national environmental quality standards, the qualities of groundwater and surface-water was overall evaluated. On the whole, the quality of deep-level groundwater was better and hazardous substances were not superstandard, F is higher, Fe and Mg was superstandard in several sites. The quality of shallow groundwater was general worse and COD, Fe, Mn, NH4^+-N, F, total hardness, total dissolved solids etc. overstep drinking water standard; the quality of surface water was worst and many indices were evidently higher, which was very worst in the east of downtown. Main pollution way of water body was lixiviation type of primary pollution groundwater and infiltration type of secondary pollution groundwater. Environmental quality assessment of plough layer soil indicated that it was better in the northwest and worse in the southeast, furthermore from Xiwu, Daguanzhang, Zhougezhuang to Pengzhuang, Dazhaolin and the north of Jingshan railroad, the environmental quality is worst.  相似文献   

6.
《《幕》》2008,31(4):422-422
William Watt Hutchison, "Hutch" to his many friends around the world, was a Scots-born Canadian geologist who served Canada and the IUGS in myriad dynamic and creative ways. Most notably, he served as the IUGS Secretary General (1976-1980) at a pivotal time in its history, and as IUGS President (1984-1987). The same boundless energy, enthusiasm, skill in communications, and ability to foster teamwork that characterized his work with the IUGS also carried him to preeminent scientific administrative positions in the Canadian Government,  相似文献   

7.
保温材料在青藏铁路路基工程中应用的数值分析   总被引:1,自引:0,他引:1  
温智  盛煜  马巍  齐吉琳  吴基春 《冰川冻土》2004,26(Z1):83-89
In many cases, preventing permafrost from further thaw due to human activities might be the first choice for embankment design in permafrost regions. 2-D finite element analysis was conducted in this paper, in which phase change was taken into consideration to simulate the thermal regime of the Qinghai-Tibetan Railway with Expandable Polystyrene (EPS). Based on the predicted maximum thaw depth in the following 50 year, the best position for insulation was presented and the relationship between the thickness of insulation and the height of embankment was analyzed. Besides, the applicable range of insulation in embankment engineering of the Qinghai-Tibetan Railway in terms of Mean Annual Air Temperature (MAAT) was suggested and the influence of geothermal field of permafrost on the applicable range of the insulation was discussed.  相似文献   

8.
Comprehensive analyses were made based on seismic prospecting data, electrical prospecting data and basin simulation data as well as regional geological data and thorough discussions were conducted about the complicated structures, features and evolution of Hefei Basin in Early Cretaceous in this study, and it was derived that that Hefei Basin was a composite basin formed during the transformation of the stress field from compressive toward tensile in Early Cretaceous. In other words, this basin was a foreland basin of gliding-thrust type, which is mainly controlled by the Dabie orogenic belt in the south side in the early to middle period of Early Cretaceous, while being a strike-slip basin of pull-apart type, which is mainly controlled by the activity of Tanlu fracture in the east side in the middle to late period of Early Cretaceous. Moreover, the potential Lower Cretaceous oil and gas system in the pull-apart basin and the vista for its prospecting were explored in this study. Tectonism of the Tanlu fracture was further discussed based on the results of characterization of the basin, and it was pointed out that this is beneficial and instructive to the oil and gas prospecting in Hefei Basin.  相似文献   

9.
<正>The formation and disruption of supercontinents have significantly impacted mantle dynamics,solid earth processes,surface environments and the biogeochemical cycle.In the early history of the Earth,the collision of parallel intra-oceanic arcs was an important process in building embryonic continents.Superdownwelling along Y-shaped triple junctions might have been one of the important processes that aided in the rapid assembly of continental fragments into closely packed supercontinents. Various models have been proposed for the fragmentation of supercontinents including thermal blanket and superplume hypotheses.The reassembly of supercontinents after breakup and the ocean closure occurs through "introversion","extroversion" or a combination of both,and is characterized by either Pacific-type or Atlantic-type ocean closure.The breakup of supercontinents and development of hydrothermal system in rifts with granitic basement create anomalous chemical environments enriched in nutrients, which serve as the primary building blocks of the skeleton and bone of early modern life forms. A typical example is the rifting of the Rodinia supercontinent,which opened up an N—S oriented sea way along which nutrient enriched upwelling brought about a habitable geochemical environment.The assembly of supercontinents also had significant impact on life evolution.The role played by the Cambrian Gondwana assembly has been emphasized in many models,including the formation of 'Trans-gondwana Mountains' that might have provided an effective source of rich nutrients to the equatorial waters,thus aiding the rapid increase in biodiversity.The planet has witnessed several mass extinction events during its history,mostly connected with major climatic fluctuations including global cooling and warming events,major glaciations,fluctuations in sea level,global anoxia,volcanic eruptions, asteroid impacts and gamma radiation.Some recent models speculate a relationship between superplumes,supercontinent breakup and mass extinction.Upwelling plumes cause continental rifting and formation of large igneous provinces.Subsequent volcanic emissions and resultant plume-induced "winter" have catastrophic effect on the atmosphere that lead to mass extinctions and long term oceanic anoxia.The assembly and dispersal of continents appear to have influenced the biogeochemical cycle,but whether the individual stages of organic evolution and extinction on the planet are closely linked to Solid Earth processes remains to be investigated.  相似文献   

10.
Effects of mercury on ecosystems and human health are well documented. Human activities have significant impacts on transport, transformation, and fate of mercury in the natural environment. In this study, a gold mining area (Tongchuan), an urban area (Xi'an), and a historical site (Qinshihuan Tomb) in Shaanxi Province, China, was chosen to study the effects of human activities on the transport, transformation, and fate of mercury in the area. Samples of atmospheric precipitate, soil, sediment, pomegranate, corn and those from wells and the rivers that flow through or flow by the city and from the mining area were collected. The EPA methods were used for sample preparation and analysis of these samples. These methods combine acid digestion, chemical reduction, purge and trap with Cold Vapor Atomic Fluorescence Spectrometry (CVAFS). Preliminary results showed high total mercury concentrations in the water samples collected from a river in Tongguan County. The total mercury concentrations ranged from 133 to 188 ng/L in the water samples collected from the rivers flowing through Xi'an City. The amount of total mercury in the soil/sediment samples which were collected in the vicinity of Xi'an ranged from 31.8 to 83.2 ng/g. The total mercury concentrations in the samples of atmospheric precipitate (including rain and snow collected from Sep. 2005 to Jan. 2006) ranged from 106-298 ng/L.  相似文献   

11.
The continuously collected cores from the Permo–Carboniferous coal-bearing strata of the eastern Ordos Basin are essential for studying the hydrocarbon potential in this region. This study adopted sedimentological and geochemical methods to analyze the sedimentary environment, material composition, and geochemical characteristics of the coal-bearing strata. The differences in depositional and paleoclimatic conditions were compared; and the factors influencing the organic matter content of fine-grained sediments were explored. The depositional environment of the Benxi and Jinci formations was lagoon to tidal flat with weakly reduced waters with low salinity and dry-hot paleoclimatic conditions; while that of the Taiyuan Formation was a carbonate platform and shallow water delta front, where the water was highly reductive. The xerothermic climate alternated with the warm and humid climate. The period of maximum transgression in the Permo–Carboniferous has the highest water salinity. The Shanxi Formation was deposited in a shallow water delta front with a brackish and fresh water environment and alternative weak reductiveness. And the paleoclimate condition is dry-hot. The TOC content in fine-grained samples was averaging 1.52%. The main controlling mechanism of organic matter in this area was the input conditions according to the analysis on input and preservation of organic matter.  相似文献   

12.
The airborne gravimetry was an important leap and innovation in the world’s history of geophysical exploration. China's first test of the airborne gravity geological survey in the onshore-offshore transitional area of the western and southern part of the Bohai Sea was successful and effective in geology. Based on the airborne gravity data, and combining previous ground gravity, seismic and drilling data etc., we carried out the geological interpretation by forward and inverse methods. The result shows that the airborne Bouguer gravity anomaly was clear, the fracture interpretation was reliable, and the inversion depth of the main geological interfaces was relatively accurate. This airborne gravity geological survey not only filled the exploring gaps in the onshore-offshore transitional area, and realized the geological and tectonic junction between the sea and the land, but also discovered four local gravity anomalies, 11 fractures and three sags or subsags, and so on. The good geological effect of airborne gravimetry not restricted by terrain condition shows that it can be served as a new geophysical method in the exploration of complex terrain physiognomy area such as mountain, jungle, desert, marsh, onshore-offshore transitional area and so on, and has an extensive application prospect in China in the future.  相似文献   

13.
The mimetic ocean environment and chemical method were used to research the bioavailability effect of humic acid on five heavy metals in sediment, including Cd, Cu, Zn, Pb and Ni. The sediment was separated into four containers with artificial seawater, and each of them had different concentrations of humic acid. The values of concentrations covered the whole range found in natural sediment (0.1%-10%). According to the 48 hours LC50 of clam and distribution coefficient, metals were added in artificial seawater, and their speciation was determined at first and then after two days' incubation. It was found the bioavailability of heavy metals was reduced in the presence of humic acid. The obvious negative effect on Zn was observed, but the influence on Cd was not remarkable. In addition, the contents of Pb and Ni increased obviously in organic phase, and they are correlative with the concentrations of humic acid.  相似文献   

14.
Potassium-rich brine in the Sichuan Basin has been much studied in recent years, but few studies have focused on the distribution and migration of salt basin and the differences of potassium formation mechanisms. This work examined the salt-gathering and potassium formation of potassium-rich brine during the Triassic in the Sichuan Basin using lithofacies palaeogeographic depiction and geochemical analyses. (1) The favorable sedimentary facies controlling the formation of potassium-rich brine during the Triassic in the Sichuan Basin are evaporation platform and restricted platform, whereas the salt basin is one of the main factors controlling the poly-salt center. (2) The distribution and migration of this salt basin were affected by certain factors. The salt basin of the Jialingjiang Formation was mainly distributed in the east and central Sichuan Basin, whereas that of the Leikoupo Formation was mainly distributed in the central and west Sichuan Basin. The sedimentary centers have gradually moved westward and become smaller. (3) Three main formation mechanisms were identified for the potassium-rich brine during the Triassic in the Sichuan Basin, i.e., evaporation and concentration of seawater, surface fresh water leaching, and deep water-rock reaction. Fresh water leaching was characterized by low anomaly δ18O and δ13C values. Water-rock reaction was mainly related to temperature, and high temperature environment (caused by burial depth, overthrust and deep hydrothermal fluids) was beneficial to water-rock reaction. The characteristics of water-rock reaction do not correspond to the increase ratio of K?103/Cl and Br?103/Cl in brine, and the Rb+ content of the brine was high. (4) The formation mechanisms of potassium-rich brine differed between different areas of the Sichuan Basin. In east Sichuan, the evaporation and concentration of seawater, together with meteoric fresh water leaching, was the main formation factor, whereas the evaporation and concentration of seawater and water–rock reaction predominated in west Sichuan. This study of the sedimentary environment and formation mechanisms is of significance to the exploration and exploitation of potassium-rich brine in the Sichuan Basin.  相似文献   

15.
Study on tectonic fractures based on the inversion of tectonic stress fields is an effective method. In this study, a geological model was set up based on geological data from the Hudi Coal Mine, Qinshui Basin, a mechanical model was established under the condition of rock mechanics and geostress, and the finite element method was used to simulate the paleotectonic stress field. Based on the Griffith and Mohr-Coulomb criterion, the distribution of tectonic fractures in the Shanxi Formation during the Indosinian, Yanshanian, and Himalayan period can be predicted with the index of comprehensive rupture rate. The results show that the acting force of the Pacific Plate and the India Plate to the North China Plate formed the direction of principal stress is N-S, NW-SE, and NE-SW, respectively, in different periods in the study area. Changes in the direction and strength of the acting force led to the regional gradients of tectonic stress magnitude, which resulted in an asymmetrical distribution state of the stress conditions in different periods. It is suggested that the low-stress areas are mainly located in the fault zones and extend along the direction of the fault zones. Furthermore, the high-stress areas are located in the junction of fold belts and the binding site of multiple folds. The development of tectonic fractures was affected by the distribution of stress intensity and the tectonic position of folds and faults, which resulted in some developed areas with level Ⅰ and Ⅱ. There are obvious differences in the development of tectonic fractures in the fold and fault zones and the anticline and syncline structure at the same fold zones. The tectonic fractures of the Shanxi Formation during the Himalayan period are more developed than those during the Indosinian and Yanshanian period due to the superposition of the late tectonic movement to the early tectonic movement and the differences in the magnitude and direction of stress intensity.  相似文献   

16.
Whether groundwater resources can be sustainably utilized is largely determined and characterized by hydrogeological parameters.Estimating the groundwater recharge is one of the essential parameters for managing water resources and protecting water resources from contamination.This study researched the spatial and temporal variation of groundwater recharge in the Thepkasattri sub-district through integrating chloride mass balance(CMB)and water table fluctuation(WTF)methods.The chloride content of representative rainfall and groundwater samples was analyzed.Besides,WTF method was adopted from groundwater level data from 2012 to 2015.According to the CMB method,the mean recharge was estimated to be 1172 mm per year,accounting for 47%of the annual rainfall.Moreover,the estimated recharge from the WTF method took 26%of annual rainfall in 2015.The recharge was underestimated according to the WTF method,because of the uncertainty in specific yield estimates and the number of representative wells in the study area.Moreover,the correlation between rainfall and water table fluctuation data indicated the positive linear relationship between two parameters.The spatial recharge prediction indicated that recharge was higher(1200-1400 mm/yr)in the eastern and western catchment,while that in the central floodplains was between 800 mm/yr and 1100 mm/yr.In addition,low recharge value between 450 mm/yr and 800 mm/yr was observed in the south-west part of Thepkasattri.The spatial variation of recharge partly reflects the influences of land use and land cover of the study area.  相似文献   

17.
The Atlas of Palaeogeography of China was published in 1955. This paper will introduce the impor- tant historical background of the compilation and publishing of the atlas. Actually it was a direct outcome of the famous Main geological structural units of China written by Huang Jiqing in 1945. Confined by the status of geological development of that stage, the atlas mainly presents the variation of the distribution of old landmasses and oceans during different geological stages. The compilation was based on facies types, palaeontological species , and features of regional fauna assemblages . The basic scale of the atlas was 1:1 000 000. There are totally 20 maps, spanning from the Sinian to Triassic of the Mesozoic. The compila-tion was finished in more than three years. The outline of landmasses and oceans, main direction of trans-gression and regression, distribution of fossils, crustal deformation, mineral deposits, as well as volcanic and glacial activities are shown with various patterns and colors  相似文献   

18.
During the Paleozoic, the Ordos area in the western North China Plate was located at the intersecting position of microplates and controlled by their interaction. The structural framework in the Ordos area, which underwent transformations in the Ordovician, the Carboniferous and the Permian respectively, was dominated by the alternation of uplift and depression. The transformations of structural framework are utilized as the clues to investigate the microplates' interacting type and its response in the Ordos area. According to the regional structural evolution, the Ordos area is simplified into an isopachous, isotropic and elastic shell model, and under proposed various boundary conditions, three series of numerical simulations corresponding to the three structural transformations are carried out to determine the detailed tectonic constraints. Numerical simulations reveal that the structure of the uplift and depression, which is similar to the actual pattern, develops only under one special boundary condition in each of the three series, indicating that the structural framework responds to the unique tectonic background. The simulation results show that in the Early Paleozoic, the L-shaped paleouplift formed nearby the southwestern corner of the Ordos area because the intensity of the compressions in the southern and western boundaries resulting from the ocean-continent collisions was similar. In the Late Paleozoic, it evolved into continent-continent (or arc-continent) interaction in the southern and northern boundaries; in the preliminary stage of the interaction, since the interface between the North China Plate and the plates on the south and north was narrow, the relative acting force was little and the regional western boundary immobile, and the structural framework in the basin was characterized by the N-S trending slender-waist-shaped uplift; as the interface between the plates expanded gradually, the extrusive force in the southern and northern boundaries of the North China Plate increased, resulting in the paleogeographic divisions showing E-W trending, and, the western boundary of the basin was extruded westward due to the intense compression inducing the local NE trending of paleogeographic division in the central area. The simulation results further reflect that the symmetry of the uplift-depression pattern is restricted by that of the boundary conditions, suggesting that the Paleozoic structural transformations of the Ordos area under boundary constraints accord with the universal physical symmetrical principle.  相似文献   

19.
In the Tuoshi oilfield,located in the Cenozoic Jianghan Basin of southeastern China ,there have been found hydrocarbon reservoirs hosted in lacustrine sandstones of the Eogene Xingouzui Formation.The main diagenetic features identified in these sandstones include the dissolution of detrital K-feldspar and albite grains,the precipitation of quartz as overgrowths and /or cements ,and the precipitation and /or transformation of clay minerals.These diagenetic features were interpreted to have occurred in early,intermediate and late stages,based on the burial depth.The kinetics of fluid-mineral reactions and the concentrations of aqueous species au each stage of diagenesis were simulated numerically for these lacustrine sandstones,using a quasi-sta-tionary state approximation that incorporates simultaneous chemical reactions in a time-space continuum.During the early diagenetic stage,pore fluid was weakly acidic,which resulted in dissolution of K-feldspar and albite and,therefore,led to the release of K^ ,Na^ ,Al^3 and SiO2(aq) into the diagenetic fluid.The increased K^ ,Na^ ,Al^3 and SiO2(aq) concentrations in the diagenetic fluid caused the precipitation of quartz,kaolinite and illite.At the beginning of the intermediate diagenetic stage the concentration of H^ was built up due to the decomposition of organic matter,which was responsible for further dissolution of K-feldspar and albite and pre-cipitation of quartz,kaolinite,and illite.During the late diagenetic stage,the pore fluid was weakly alkaline,K-feldspar became stable and was precipitated with quartz and clay minerals.When the burial depth was greater than 3000 m,the pore fluids became supersaturated with respect to allbite,but undersaturated with respect to quartz,resulting in the precipitation of albite and the dissolution of quartz.The diagenetic reactions forecasted in the numerical modeling closely matched the diagenet-ic features identified by petrographic examination, and therefore,can help us to gain a better understanding of the diagenetic processes and associated porosity evolution in sandstone reservoirs.  相似文献   

20.
Abstract: The present paper examines the changing climatic scenarios and associated effects on livestock farming (pastoralism) in the arid and semi arid lands (ASAL) of Kenya, which cover over 80% of the country. The study was carried out in the semi arid Mukogodo Division of Laikipia District in Kenya. This division received a mean annual rainfall of approximately 507.8?mm and the main source of livelihood was pastoralism. Questionnaire, structured interview, observation and literature review were the main methods of data collection. Rainfall was used in delineating changes in climate. Standardized precipitation index (SPI) and Markov process were used in analyzing drought severity and persistence, respectively. Approximately 38% of all droughts between 1975 and 2005 were prolonged and extremely severe, with cumulative severity indices ranging between ?2.54 and ?6.49. The probability that normal climatic conditions persisted for two or more consecutive years in Mukogodo Division remained constant at approximately 52%. However, the probability of wet years persisting for two or more years showed a declining trend, while persistence of dry years increased with duration. A drying climatic trend was established. This drying trend in the area led to increased land degradation and encroachment of invasive nonpalatable bushes. The net effect on pastoralism was large-scale livestock loss through starvation, disease and cattle rustling. Proper drought monitoring and accurate forecasts, community participation in all government interventions, infrastructural development in the ASAL and allocation of adequate resources for livestock development are some of the measures necessary for mitigating the dwindling pastoral economy in Kenya and other parts of the world.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号