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五角大楼为红外成象“幼畜”导弹提供经费
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作者 《中国航天》 1981年第2期82-83,共2页
据《航讯》一九八一年二月三日报导:五角大楼一九八二财政年度的预算申请包括购买休斯公司牛产的第一批490枚红外成象“幼畜”空地导弹的费用2.12亿美元。
关键词 红外成象 美国空军 一九 电视制导 反辐射导弹 土事 萨斯
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100期,依然是个开始
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作者 徐洛屹 《门窗》 2015年第4期1-1,共1页
"门前老村长新茅,院里枯木又开花",在这首略带伤感耳熟能详的《时间都去哪儿了》的歌曲中,春天就这么突然的来了,而《门窗》杂志也即将走过她的第100期时交岁月。在近九年的时间里,一篇篇论文、一条条资讯,帮助了无数从业者,... "门前老村长新茅,院里枯木又开花",在这首略带伤感耳熟能详的《时间都去哪儿了》的歌曲中,春天就这么突然的来了,而《门窗》杂志也即将走过她的第100期时交岁月。在近九年的时间里,一篇篇论文、一条条资讯,帮助了无数从业者,而《门窗》也越办越成熟。从创刊起,我们的每一个脚步都紧随着门窗行业发展的坚实步伐。近几年来,为适应行业的不断发展壮大以及创新和转型升级的需求,《门窗》 展开更多
关键词 去哪儿 长新 旄星 波本 和龙 土事 要会
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以办公室的名义行文为妥
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作者 武春 《法治与社会》 2015年第12期35-35,共1页
按传统惯例,机关、企业事业单位和社会团体都有自己的公章,都可以发文。根据人大机关公文处理办法第十二条的规定,人大机关发文时,应当加盖发文机关印章。但值得注意的是,人大常委会主任会议不是机关,更不是企业事业单位和社会团体,因... 按传统惯例,机关、企业事业单位和社会团体都有自己的公章,都可以发文。根据人大机关公文处理办法第十二条的规定,人大机关发文时,应当加盖发文机关印章。但值得注意的是,人大常委会主任会议不是机关,更不是企业事业单位和社会团体,因而各级人大常委会主任会议都没有自己的公章。由于主任会议不是机关,也没有自己的公章。 展开更多
关键词 十二条 公文处理办法 地方组织法 土事
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APPLICATION OF WRF/UCM IN THE SIMULATION OF A HEAT WAVE EVENT AND URBAN HEAT ISLAND AROUND GUANGZHOU 被引量:3
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作者 蒙伟光 张艳霞 +3 位作者 李江南 林文实 戴光丰 李昊睿 《Journal of Tropical Meteorology》 SCIE 2011年第3期257-267,共11页
This paper evaluated the performance of a coupled modeling system,Weather Research and Forecasting(WRF)/Urban Canopy Model(UCM),in the simulation of a heat wave event which occurred around Guangzhou during late June t... This paper evaluated the performance of a coupled modeling system,Weather Research and Forecasting(WRF)/Urban Canopy Model(UCM),in the simulation of a heat wave event which occurred around Guangzhou during late June through early July,2004.Results from three experiments reveal that the UCM with new land data(hereafter referred to as E-UCM)reproduces the best 2-m temperature evolution and the smallest minimum absolute average error as compared with the other two experiments,the BPA-Bulk Parameterization Approach with new land data(E-BPA)and the UCM with original U.S. Geological Survey land data(E-NOU).The E-UCM is more useful in capturing the temporal and spatial distribution of the nighttime Urban Heat Island(UHI).Differences in surface energy balance between the urban and suburban areas show that low daytime albedo causes more absorption of solar radiation by urban areas.Due to the lack of vegetation which inhibits cooling by evapotranspiration,most of the incoming energy over urban areas is partitioned into sensible heat flux and therefore heats the surface and enhances the heat wave.During nighttime,the energy in the urban area is mainly from soil heat flux.Although some energy is partitioned as outgoing long wave radiation,most of the soil heat flux is partitioned into sensible heat flux due to the small latent heat flux at night.This leads to the development of nighttime UHI and the increase of the magnitude and duration of heat waves within the municipality. 展开更多
关键词 heat wave Urban Heat Island(UHI) Urban Canopy Model(UCM) numerical simulation
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A Case Study of a Typical Dust Storm Event over the Loess Plateau of Northwest China
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作者 LING Xiao-Lu GUO Wei-Dong +1 位作者 ZHAO Qian-Fei ZHANG Bei-Dou 《Atmospheric and Oceanic Science Letters》 2011年第6期344-348,共5页
Enhanced observational meteorological elements,energy fluxes,and the concentration of dust aerosols collected from the Semi-Arid Climate Observatory and Laboratory(SACOL) during a typical dust storm period in March 20... Enhanced observational meteorological elements,energy fluxes,and the concentration of dust aerosols collected from the Semi-Arid Climate Observatory and Laboratory(SACOL) during a typical dust storm period in March 2010 at Lanzhou were used in this paper to investigate the impact of dust aerosols on near surface atmospheric variables and energy budgets.The results show that the entire dust storm event was associated with high wind velocities and decreasing air pressure,and the air changed from cold and wet to warm and dry and then recovered to its initial state.The response of energy fluxes occurred behind meteorological elements.At high dust concentration periods,the net radiation was significantly less in the daytime and higher at night,while the heat fluxes displayed the same trend,indicating the weakening of the land-atmosphere energy exchange.The results can be used to provide verification for numerical model results in semi-arid areas. 展开更多
关键词 case study dust storm energy budget Loess Plateau
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The Morphological Analysis of Folktales of Tu Nationality in Hehuang Region in Northwest China
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作者 ZHAO Zhi-yi 《Journal of Literature and Art Studies》 2016年第11期1293-1303,共11页
The Tu nationality (also called "Tu people" or "Tus" in the paper), one of the multiple ethnic minorities in the Hehuang Region (河湟地区) between Gansu (甘肃) and Qinghai (青海) Provinces in the northwest... The Tu nationality (also called "Tu people" or "Tus" in the paper), one of the multiple ethnic minorities in the Hehuang Region (河湟地区) between Gansu (甘肃) and Qinghai (青海) Provinces in the northwest China, has no written language of their own, but has already created the abundant and varied colorful literary genres. Since the 1980s, folktales, as the main literary product popular in the region, have received literary criticisms and reviews from scholars and researchers in China, based on the socialist realism dominant in China in the 20th century that emphasized more on contents, motifs and even ideological significance. So far, no breakthroughs have been made in their studies even if some young scholars have tried from the formalist viewpoints. Therefore, this paper attempts to make a morphological analysis of the Tus' folktales by adopting Propp's theories, trying to find out the morphological narrative model beneath the language level of the folktales. Through the studies, we can see that collective awareness bonded by kinship is more emphasized in Tus' culture, and almost all tales end with good defeating evil. Therefore, the studies of these folktales will help us deep understand Tus' psychological conditions and positive cultural life. 展开更多
关键词 morphological analysis folktales of Tu nationality Hehuang Region Propp's theory creative rules collectiveness
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Informally Established Relations Between the Superior and the Subordinate: Turkey's Example
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作者 Sinan Caya 《Sociology Study》 2015年第5期354-359,共6页
Turkish people display deep consideration for the concept of hierarchy. Historically, they had been always calculating and measuring the relative positions of authority symbols with respect to one another; because the... Turkish people display deep consideration for the concept of hierarchy. Historically, they had been always calculating and measuring the relative positions of authority symbols with respect to one another; because they had their own dealings with those who held political power. Should they render their young sons to the service of the feudal lords or the state? Should they consent to the say of the local forces or that of the central state power, when it comes to fixing the amounts and/or the kinds of taxes? Sometimes, the ordinary subjects of the Ottoman state were even openly torn apart in dilemmas whereby local powers were revolting against the central government of the Sultan placed at the capitol. Even the anoymous folk tales, which reflect people's opinions and mentalities in a manner very close to the truth, involve comparisons among the levels of power represented by certain officials/figures. When confronted with authority, the usual feeling contains a tint of respect, even though it is mainly a kind of resignition mixed with acceptance, leading to obedience in the end. A true, internalized respect itself is solely that which is directed toward the elderly people of the society. On the other hand, traditionally and conventionally, old age was closely associated with official or informal power and authority, anyhow. However, nowadays, in a very confusing manner, this former social understanding is undergoing rather fast changes with the advent of younger contemporary political figures. 展开更多
关键词 TURKEY HIERARCHY society informal (ways)
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A Regional-Scale Method of Forecasting Debris Flow Events Based on Water-Soil Coupling Mechanism 被引量:8
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作者 ZHANG Shao-jie WEI Fang-qiang +2 位作者 LIU Dun-long YANG Hong-juan JIANG Yu-hong 《Journal of Mountain Science》 SCIE CSCD 2014年第6期1531-1542,共12页
A debris flow forecast model based on a water-soil coupling mechanism that takes the debrisflow watershed as a basic forecast unit was established here for the prediction of disasters at the watershed scale.This was a... A debris flow forecast model based on a water-soil coupling mechanism that takes the debrisflow watershed as a basic forecast unit was established here for the prediction of disasters at the watershed scale.This was achieved through advances in our understanding of the formation mechanism of debris flow.To expand the applicable spatial scale of this forecasting model,a method of identifying potential debris flow watersheds was used to locate areas vulnerable to debris flow within a forecast region.Using these watersheds as forecasting units and a prediction method based on the water-soil coupling mechanism,a new forecasting method of debris flow at the regional scale was established.In order to test the prediction ability of this new forecasting method,the Sichuan province,China was selected as a study zone and the large-scale debris flow disasters attributable to heavy rainfall in this region on July 9,2013 were taken as the study case.According to debris flow disaster data on July 9,2013 which were provided by the geo-environmental monitoring station of Sichuan province,there were 252 watersheds in which debris flow events actually occurred.The current model predicted that 265 watersheds were likely to experience a debris flow event.Among these,43 towns including 204 debrisflow watersheds were successfully forecasted and 24 towns including 48 watersheds failed.The false prediction rate and failure prediction rate of thisforecast model were 23% and 19%,respectively.The results show that this method is more accurate and more applicable than traditional methods. 展开更多
关键词 Debris flow Forecasting Water-soil coupling mechanism WATERSHED
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Historical Analogy: Japan's Road Toward War and Japan's Postwar Road
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作者 Wang Xiaoran C. X. George Wei 《Cultural and Religious Studies》 2016年第9期553-563,共11页
In 1931, Japan launched the Sept. 18th attack against China. Ever since, there have been many different views over the origin of Japan's road toward war, which mostly concern with Japan's land policy. This paper hol... In 1931, Japan launched the Sept. 18th attack against China. Ever since, there have been many different views over the origin of Japan's road toward war, which mostly concern with Japan's land policy. This paper holds that Japan's land policy was an evolving one and it transformed along the change of its supporters and implementers during different stages. It is mostly a contention about the different strategies on Manchuria and Mongol; the northward or the southward advance faction; the orientations of the radical military occupation or the moderate economic occupation. Interestingly, the development of Japan's postwar policy toward China, especially in the recent years, resembles the evolvement of Japan's land policy in the 19th century. They both show tendency from the economic effort to the military activity. 展开更多
关键词 Japan's land policy imperial defense strategy Shidehara diplomacy financial occupation
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Participatory Planning of Social and Spatial Organization in Agrarian Reform Policy in Brazil: An Assessment of the Implementation Challenges
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作者 Leandro Frederico Ferraz Meyer Marcelo Jose Braga +1 位作者 Francy Mary Costa Cleria Figueiredo 《Journal of Civil Engineering and Architecture》 2013年第9期1177-1188,共12页
The social endeavors for Agrarian Reform in Brazil have a history of at least sixty years. Throughout this time, distinct political regimes, increased land concentration, disordered urbanization and the development of... The social endeavors for Agrarian Reform in Brazil have a history of at least sixty years. Throughout this time, distinct political regimes, increased land concentration, disordered urbanization and the development of a dynamic agribusiness sector inserted in global economy led to both the aggravation of social conflicts over land in Northern and Southern Brazil as well as new inquiries on the features necessary for an efficient Agrarian Reform Plan in the authors' country. Focused on the agrarian reform projects in the Brazilian Amazon, this work discusses on the political and methodological perspectives drawn in II PNRA (second National Plan of Agrarian Reform). The authors frame their account mostly along the theoretical scaffolding provided by the Bloomington School of Institutional Analysis. The authors analyze the multiple challenges facing the organization and the maintenance of the institutional structure designed to facilitate participatory planning and governance of collective resources in periurban settlements. The authors portrait these settlements as highly complex socio-ecological systems wherein socioeconomic asymmetries, cultural diversity and poor social capital and education promote political and ideological disputes that jeopardize safeguarding global commons. 展开更多
关键词 Agrarian Reform participatory planning social dilemmas institutional analysis AMAZON Brazil.
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Potential Renaturalisation of Lakes as An Element Building Up Water Resources: An Example of Mosina Lake, Poland 被引量:1
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作者 Ptak MARIUSZ 《Chinese Geographical Science》 SCIE CSCD 2017年第1期8-12,共5页
Water deficits observed in many regions of the world make it necessary to implement measures intended to improve this situation. Poland is one of the countries with the poorest water resources in Europe due to its nat... Water deficits observed in many regions of the world make it necessary to implement measures intended to improve this situation. Poland is one of the countries with the poorest water resources in Europe due to its natural conditions and human impact. As a result of land reclamation carried out over decades, many elements of its hydrographic system have been changed, and some of them, like lakes, have disappeared altogether. In the days of the socio-economic transformation and more frequent extreme events, what seems worth considering is the renaturalisation of non-existing lakes, an idea presented in this paper on a selected example. 展开更多
关键词 environment transformation drainage water resources human activity Mosina Lake Poland
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A Study of Soil-dynamics Based on a Simulated Drought in an Alpine Meadow on the Tibetan Plateau 被引量:4
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作者 WANG Zhi-yuan SUN Geng +2 位作者 LUO Peng MOU Cheng-xiang WANG Jun 《Journal of Mountain Science》 SCIE CSCD 2013年第5期833-844,共12页
Extreme weather events have played an important role in driving the ecosystem dynamics in high altitude areas, but the underlying mechanism remains unclear. To understand if and how the soil processes of an ecosystem ... Extreme weather events have played an important role in driving the ecosystem dynamics in high altitude areas, but the underlying mechanism remains unclear. To understand if and how the soil processes of an ecosystem react to extreme drought, we manipulated a once-in-a-century meteorological extreme drought in an alpine meadow on the Tibetan Plateau, which is also known as the "forerunner of global weather changes". The extremity was determined by statistical extreme weather events with respect to a historical reference period from April to September during 1962 - 2004, where the local historical precipitation data was calculated and intensified to loo-year recurrent drought event with Gumbel I distribution. The indicators we measured included soil microbial biomass C/N/P and soil enzymatic activities of phosphatase (AP) disbounding organic phosphate, cellobiohydrolase (CBH), β- glucocidase (BG), N-releasing enzyme N-acetyl- glucosaminidase (NAG) as well as soil respirations, during and after the treatments. It was found that the manipulated event induced a rapid shift in microbial biomass and activities, indicating a lower resistance of the underground process. However, the microbial and biochemical parameters saw rapid recovery after the event, which meant the soil processes enjoyed high resilience. The high responsiveness and lag-time effects of the soil indicators rendered new horizons for us to evaluate the interaction between the extremes and the ecosystem stability. Our study indicated that the once-in-a-century extreme drought induced very short term response in the soil biotic process, and the soil processes worked to buffer against such events under the observation period. 展开更多
关键词 Extreme weather event Soil enzyme Microbial biomass Nutrient availability
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The Drainage Exchange of Stormwater Potential in Flat Area Problems
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作者 S. Musa N.A. Zakaria +1 位作者 S.H. Lai D. Tjahjanto 《Journal of Environmental Science and Engineering》 2010年第10期1-8,共8页
Groundwater as an alternative source still does not contribute to the water supply in area of Parit Raja because of the limitation of water availability in the ground. This lacking of groundwater could be caused by th... Groundwater as an alternative source still does not contribute to the water supply in area of Parit Raja because of the limitation of water availability in the ground. This lacking of groundwater could be caused by the circumstance that the top layer of soil is dominated by compacted clay around 2 meters in which its permeability is small, so the water is difficult to infiltrate the ground. The recharge well technique was designed based on the flat area problems, layer of real condition, flow water table and low infiltration rate. Resistivity soundings were made at existing wells to assess the subsurface layers. Beside that, the past records on floods event, sub surface and surface studies were collected around study area as a preliminary studies. It was presented that the study area promised good prospects to increase the capability of groundwater and contribute to the drainage system by reducing the volume of rainfall runoff using the recharge well technique. 展开更多
关键词 GROUNDWATER recharge well water supply drainage system
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Surface Soil Moisture Simulation for a Typical Torrential Event with a Modified Noah LSM Coupling to the NWP Model
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作者 ZHENG Zi-Yan ZHANG Wan-Chang +2 位作者 XU Jing-Wen YAN Zhong-Wei LU Xue-Mei 《Atmospheric and Oceanic Science Letters》 2011年第1期18-23,共6页
Surface soil moisture has great impact on both meso-and microscale atmospheric processes,especially on severe local convection processes and on the dynamics of short-lived torrential rains.To promote the performance o... Surface soil moisture has great impact on both meso-and microscale atmospheric processes,especially on severe local convection processes and on the dynamics of short-lived torrential rains.To promote the performance of the land surface model (LSM) in surface soil moisture simulations,a hybrid hydrologic runoff parameterization scheme based upon the essential modeling theories of the Xin'anjiang model and Topography based hydrological Model (TOPMODEL) was developed in preference to the simple water balance model (SWB) in the Noah LSM.Using a strategy for coupling and integrating this modified Noah LSM to the Global/Regional Assimilation and Prediction System (GRAPES) analogous to that used with the standard Noah LSM,a simulation of atmosphere-land surface interactions for a torrential event during 2007 in Shandong was attempted.The results suggested that the surface,10-cm depth soil moisture simulated by GRAPES using the modified hydrologic approach agrees well with the observations.Improvements from the simulated results were found,especially over eastern Shandong.The simulated results,compared with the products of the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) soil moisture datasets,indicated a consistent spatial pattern over all of China.The temporal variation of surface soil moisture was validated with the data at an observation station,also demonstrated that GRAPES with modified Noah LSM exhibits a more reasonable response to precipitation events,even though biases and systematic trends may still exist. 展开更多
关键词 soil moisture Noah LSM hydrologic runoff parameterization Numerical Weather Prediction (NWP) model
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Aesthetic art development and protection of Tujia waving dance in Hunan Province
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作者 Xinyuan Guo 《International Journal of Technology Management》 2013年第6期124-126,共3页
Tujia dance is an advanced, special form of human aesthetic activities. The so-called aesthetic, simply put, is to feel, and understand the objective things or phenomena presented by the United States itself: specifi... Tujia dance is an advanced, special form of human aesthetic activities. The so-called aesthetic, simply put, is to feel, and understand the objective things or phenomena presented by the United States itself: specifically, it refers to the people in their social practice and objective process of historical things or phenomena occur and construct a special performance relationship. There are basically three kinds of relationships of man and objective things or phenomena: firstly, cognitive relation of science; Secondly, ethical norms relations; thirdly, aesthetic performance relationship. Focus on the relationship between the performances of the aesthetic object vivid sense of the expressive form of regularity is the unity and purpose, with freedom. The essence of aesthetic is liberty. Art aesthetic and general aesthetic are different, mainly because of its aesthetic objects, which is based on works of art as an aesthetic object. General aesthetic contemplation of beauty of reality, the reality of objective things or phenomena, not as people practice the original object mad the object of knowledge exists. In social practice, they first form a rational understanding of relationships and will practice relationship. On this basis, when the society develops to the degree of no direct utilitarian attitude, practical attitude towards the object of an object only when there has been more mature, purely aesthetic relationship. The beauty of art is different from the reality beauty, which is produced and existed as an aesthetic object. 展开更多
关键词 Aesthetic art Tujia dance Protection.
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Discuss on Damage of the Reputation Right and Legal Responsibility
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作者 Ying Li Shiying Zhu Jichao Liu 《International English Education Research》 2014年第3期72-74,共3页
The reputation is within the scope of personal fights, and the reputation of civil subject is protected by law. Identification of acts of defamation must be based on facts and law. If the perpetrator with a non-legiti... The reputation is within the scope of personal fights, and the reputation of civil subject is protected by law. Identification of acts of defamation must be based on facts and law. If the perpetrator with a non-legitimate means damages the reputation of the civil subject, with some impact, the actor should bear civil liability. Meanwhile, there are problems in right identifying defamation, such defenses, an identification of violation of corporate reputation, the reputation of the deceased identified violations and fi'eedom of the press, public opinion against the reputation of the finds, etc., whose solving is significant for practical guidance. 展开更多
关键词 Right Reputation Identification Key Component
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字形排检法 被引量:1
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作者 杜定友 《语文建设》 1961年第Z1期43-45,共3页
二、检法1.检字时,先看该字属于那一个字形? (1) ○单体字:一个单组织的字,单组织也叫作“字根”,是汉字最小的单位,如: “斗农心义州一平王天土事臣两木戈东大百而卫子上口里四中串水八人九禹丹川儿”注:字根是不能再分拆的,如:“大”... 二、检法1.检字时,先看该字属于那一个字形? (1) ○单体字:一个单组织的字,单组织也叫作“字根”,是汉字最小的单位,如: “斗农心义州一平王天土事臣两木戈东大百而卫子上口里四中串水八人九禹丹川儿”注:字根是不能再分拆的,如:“大”不能拆为“人一”,“天”不能拆为“一大”。但“主”可拆为“、王”,“立”可拆为“亠(?)”,作上下字。(2) (?) 左右字:一个多组织的字。 展开更多
关键词 单体字 排检法 卫子 义州 土事 丹川 卜日 互见法 重禹 下字
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领导干部要多干一些让上级党委放心的事
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作者 周云 《西南民兵》 2002年第7期19-19,共1页
作为民兵预备役工作一线指挥部的县级人武部,其驻地大都比较偏远,“山高皇帝远”正是人武部远离上级机关和上级领导的真实写照。在这种情况下,作为人武部主官,如何践行“四自”要求,自觉管好自己和部属。
关键词 一线指挥部 预备役工作 “四自” 领导干部 庄友 土事 国家级贫困县 不知道 车军
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Effects of Pits and Mounds Following Windthrow Events on Soil Features and Greenhouse Gas Fluxes in a Temperate Forest 被引量:4
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作者 Yahya KOOCH Sakineh Mollaei DARABI Seyed Mohsen HOSSEINI 《Pedosphere》 SCIE CAS CSCD 2015年第6期853-867,共15页
Pit and mound micro-relief(resultant microsites from trees uprooted by windthrow) could have regimes of microclimate and soil features that differ from areas of undisturbed soil. In an attempt to provide a comprehensi... Pit and mound micro-relief(resultant microsites from trees uprooted by windthrow) could have regimes of microclimate and soil features that differ from areas of undisturbed soil. In an attempt to provide a comprehensive evaluation of the significance of pits and mounds on soil features and also the dynamics of greenhouse gas(GHG) fluxes at local scale, this study was carried out in a reserved area of Darabkola forest in Mazandaran Province, northern Iran. The age of a pit and mound was considered equal to the degree of decay of the blown down tree. Three microsites were distinguished, consisting of pit bottom(PB), mound top(MT) and undisturbed area(UA). Soil samples were taken at 0–15 and 15–30 cm depths from all microsites and analysed for soil physical, chemical and biological features. Our findings suggested that in context of forest ecology, pits and mounds following windthrow events should be considered as an effective factor influencing soil features(i.e., density, texture, water content, p H, organic C, total N, available nutrients and earthworm density/biomass) and especially GHG fluxes. Results showed that MT acted as a sink for N2O(-0.010 mg N2 O m-2d-1) and CH4(-0.257 mg CH4m-2d-1) fluxes and also produced lower CO2 concentrations(0.095 mg CO2 m-2d-1) than PB(0.207 mg CO2 m-2d-1) and UA(0.098 mg CO2 m-2d-1). As a consequence, a separation into pits/mounds would be important for a precise budgeting of greenhouse gases. 展开更多
关键词 carbon dioxide methane microsite nitrous oxide oriental beech uprooted tree
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Rare earth element and yttrium compositions of the Paleoproterozoic Yuanjiacun BIF in the Lüliang area and their implications for the Great Oxidation Event(GOE) 被引量:14
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作者 WANG ChangLe ZHANG LianChang +1 位作者 LAN CaiYun DAI YanPei 《Science China Earth Sciences》 SCIE EI CAS 2014年第10期2469-2485,共17页
In China, most Precambrian banded iron formations (BIFs) are situated in the North China Craton. The Yuanjiacun iron depos- it, located in the Ltlliang area, is arguably the most representative Superior-type BIF. Th... In China, most Precambrian banded iron formations (BIFs) are situated in the North China Craton. The Yuanjiacun iron depos- it, located in the Ltlliang area, is arguably the most representative Superior-type BIF. This iron deposit is coherent with the sedimentary rock succession of the Yuanjiacun Formation in the lower Lliliang Group, and was interpreted to be deposited at 2.3-2.1 Ga, based on ages of overlying and underlying volcanic strata. This age overlaps with the time range of the Great Oxidation Event (GOE, 2.4-2.2 Ga). The Yuanjiacun BIF consists mainly of subhedral-xenomorphic magnetite and quartz and rarely other minerals with a lower degree of metamorphism, from greenschist to lower amphibolite facies. The geochemical characteristics of this BIF are similar to those of Superior-type BIFs. Prominent positive La, Y, and Eu anomalies normalized by the Post Archean Australian Shale (PAAS) indicate that the primary chemical precipitate is a result of solutions that repre- sent mixtures of seawater and high-T hydrothermal fluids. The contamination from crustal detritus found is negligible based on low abundances of Al2O3 and TiO2 (〈0.5%) and of trace elements such as Th, Hf, Zr, and Sc (〈1.5 ppm), as well as the lack of co-variations between Al2O3 and TiO2. In particular, the Yuanjiacun BIF samples do not display significant negative Ce anom- alies like those of the Archean iron formations, but rather, the Yuanjiacun BIF samples exhibit prominent positive Ce anoma- lies, low Y/Ho ratios, and high light to heavy REE ((Pr/Yb)sN) ratios, which are essentially consistent with the late Paleoprote- rozoic (〈2.0 Ga) BIFs around the world. These characteristics of the Yuanjiacun BIF samples imply that the ancient ocean (2.3-2.1 Ga) was redox-stratified from oxic shallow water to deeper anoxic water. The specific redox conditions of the ancient ocean may be related to the GOE, which gave rise to the oxidation of Ce and Mn in the upper water, and to the presence of a Mn oxide shuttle in the ocean, resulting in varying REE patterns due to the precipitation and dissolution of this Mn oxide shut tle under different redox states. Therefore, the Yuanjiacun BIF appears to have formed near the redoxcline and lower-level reduced marine water. 展开更多
关键词 Yuanjiacun iron deposit geochemistry of BIFs Great Oxidation Event (GOE) Mn hydroxide shuttle precipitationmechanism
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