石英脉型辉钼矿矿床多建造地球化学异常特征   总被引：1，自引：0，他引：1  

朱柏松  王成良  张方君 《物探与化探》2004,28(2):114-115,118

通过对石英脉型辉钼矿床水系沉积物和区域成矿带多建造地球化学异常特征的研究,为寻找石英脉型钼矿床提供地球化学论据。  相似文献   

承压水减压引起的沉降分析   总被引：7，自引：0，他引：7  

骆冠勇  潘泓  曹洪  尹小玲 《岩土力学》2004,25(Z2):196-200

由下卧承压水层减压引起的固结沉降计算与一般的由堆载或潜水位下降引起的固结沉降计算不同,本文着重研究了在深厚弱透水层下卧强透水承压层的复杂地质条件下,下卧承压水层减压引起的土中应力变化及周围地表沉降的计算方法;在假定一维竖向固结的条件下推导了减压引起的沉降固结度计算公式,该公式与常规的双向排水固结公式相同,表明排水减压固结与常规的双向排水固结有着相同的效果.最后,将此分析方法应用于潮州供水枢纽工程西溪水闸沉降分析中,实践的结果表明,该方法简单可行,能较好地满足工程要求.  相似文献   

Hydro-thermal performance of multilayer capillary barriers in arid lands     

A. M. O. Mohamed  I. Shooshpasha 《Geotechnical and Geological Engineering》2004,22(1):19-42

In this study, a capillary barrier system was designed and tested for an arid land environment. To simulate arid land conditions of high temperature and sub-irrigation systems, the barrier was subjected to thermal and hydraulic gradients in opposite directions; to test the barrier system under these severe conditions, an experimental apparatus was designed and fabricated. The multilayer capillary barrier consisted of three layers made of silica sand, a mixture of sand and bentonite in equal portions, and a mixture of clay (25%) and aggregate (75%). Several one dimensional coupled heat and moisture tests were performed. Temperature variations along the thickness of the barrier were recorded as a function of time, and at the end of each test, the barrier was sliced into small sections, for the determination of volumetric water content as a function of distance from the heat source. The experimental results were discussed in view of the barrier's intended purpose of its ability to store moisture for long time durations. Coupled heat and moisture flow equations were developed and solved numerically via a finite difference method. Diffusivity parameters were calculated by using experimental results, a numerical model, and Powell's conjugate directions method of nonlinear optimization. The model was calibrated and the results were discussed. Good agreement between calculated and experimental results was obtained. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

长江流域水资源、灾害及水环境状况初步分析   总被引：1，自引：0，他引：1  

姜加虎  王苏民 《第四纪研究》2004,24(4):512-517

长江是我国第一、世界第三大河流,发源于青藏高原,全长6300多公里,流域面积180×104km²,占中国陆地面积的1/5。长江及其流域不仅以其不可替代的自然资源优势和其他江河无法比拟的区位优势,在我国国民经济和社会发展中扮演着举足轻重的角色,特别是约占全国的36%、拥有9616×10⁸m³的年径流量(为黄河的20倍),是我国最重要的水源地。这不仅对长江流域资源优势的发挥和缓解我国北方地区日趋严重的水资源短缺问题至关重要,而且对全国的可持续发展也将产生深远影响。然而,在长江流域大规模开发及经济快速发展的同时,人类活动与自然规律的负面效应相互叠加,导致了流域环境的生态调节和自我恢复功能大幅降低,引起了日趋严重的水环境退化、洪涝灾害威胁加剧等问题。文章首先对长江流域水资源的重要性及其作用做了分析,肯定了其丰富的资源和重要的战略地位,该流域在占全国不足18%的土地上,集中了40%以上的人口及国民生产总值,而且其经济地位有进一步上升的趋势,在水量及水能的蕴藏上,全流域湖泊面积达10323km²,占我国淡水湖泊总面积的37.2%,水能蕴藏总计达2.7×10⁸kW。另外,对长江流域日趋严重灾害及水环境问题做了探讨,尤其中游的洪水、淤积以及随着经济发  相似文献   

晚更新世晚期以来的长江上游古洪水记录   总被引：4，自引：2，他引：4       下载免费PDF全文

葛兆帅  杨达源  李徐生  任朝霞 《第四纪研究》2004,24(4):555-560

长江上游三峡河段主要的古洪水记录有:1)三峡深槽的蚀积变化;2)长江阶地粗粒沉积;3)长江的泛滥沉积;4)长江的古洪水平流沉积。不同时间跨度不同类型古洪水记录的精度有较大的差别。古洪水记录显示,晚更新世晚期的40～30kaB.P.,长江上游大洪水比30kaB.P.以来的长江上游大洪水大得多;全新世以来,以3983aB.P.前后的大洪水为相对最大;公元1870年大洪水为3000aB.P.以来最大洪水;近百年来的实测洪水以公元1981年洪水为最大。  相似文献   

太湖生态环境演化及其原因分析   总被引：2，自引：1，他引：2       下载免费PDF全文

秦伯强  罗潋葱 《第四纪研究》2004,24(4):561-568

太湖地处长江下游三角洲,水域面积为2338km²,平均水深1.9m,最大水深不足2.6m,为一典型的大型浅水湖泊。太湖流域地势平坦,河网密布,河湖水力关系复杂。其主要补给径流来自西南部的天目山区及西部的宜溧河流域。每年夏天,大部分入湖洪水通过位于东太湖的太浦河及东北部的望虞河分别排入黄浦江与长江,由于出入湖河道的特殊位置,使得太湖南部的换水周期较短而北部较长。近几十年来,太湖由于污染而逐步呈现富营养化特征,污染物主要来自北部的无锡市和常州市,通过河道排入太湖北部的五里湖与梅梁湾,因此上述两地的水质较南部差。在东太湖,水产养殖对水环境的影响很大,亦呈现出富营养化特征,并殃及该地区的供水,加之该地区为太湖主要的泄洪通道,因此泥沙淤积严重,而且水生植物生长旺盛,呈现出明显的沼泽化趋势;在太湖四周地区,由于湖泊围垦和水利工程建设,其污染净化能力将降低,从而加速水环境恶化的趋势。太湖所面临这些问题,有待于强化湖泊科学管理来解决。  相似文献   

Iron-Titanium Oxide Geothermometry and Petrogenesis of Lava Flows and Dykes from Mandla Lobe of the Eastern Deccan Volcanic Province, India     

Mansoor Ahmad  J.P. Shrivastava   《Gondwana Research》2004,7(2):563

Compositional studies on different forms of magnetite, ulvospinel, ilmenite and hematite mineral phases occurring in 37 lava flows and 6 dykes of the Mandla lobe are presented in this paper. Ilmenite (0001) in equilibrium with titanomanetite show high values of temperature of equilibration, ranging from 1172–974°C, for high alumina quartz normative tholeiitic lava flows of Chemical Type - A; 1129–1229°C for low alumina quartz normative tholeiitic lava flows of Chemical Type - B; 1283–1124°C for tholeiitic lava flows of Chemical Type - F and 1243°C and 99O°C for two diopside olivine normative tholeiite flows of Chemical Type D. High olivine normative flows of Chemical Type - G and H show 1095°C and 1092°C respectively. Whereas, high hypersthene normative tholeiite flow of Chemical me C shows temperature of 1187°C. Data plots disposition over iron-titanium oxide equilibration temperature vs – logfo₂, diagram for Mandla lava flows and other parts of the Deccan (Igatpuri, Mahabaleshwer, Nagpur and Sagar areas) revealed that tholeiitic (evolved) basalt of the eastern Deccan volcanic province formed at high temperatures whereas, picritic (primitive) lavas of Igatpuri and tholeiitic basalt of Mahabaleshwar areas were formed at low temperatures. Mahabaleshwer basalts follow FMQ (fayalite-magnetite-quartz) buffer curve but, plots of the Mandla basalts lie above this curve indicating higher temperatures of crystallisation of ilmenite-titanomagnetite than that of the lava flows from other parts of Deccan 'Raps. The eastern Deccan Traps are most evolved types of lava as characterised by its low Mg-number and Ni content whereas, Igatpuri lava flows are picritic (primitive), having high Mg-number and Ni contents. Temperature vs FeO + Fe₂O₃ / FeO + Fe₂O₃ + MgO ratio data plots for Mandla and other Deccan lava flows and liquidus data for Hawaiian tholeiites, indicated that Igatpuri basalts lie parallel to the liquidus line of Hawaiian tholeiite but at lower temperatures. Large data plots of Mandla lava flows lie along the liquidus line of the Hawaiian lava. The highly vesicular nature of compound lava flows having large amount of volatile is responsible for low temperature values whereas, lava flows represented by high temperatures show high modal values of glass and opaque minerals.  相似文献   

A furrow runs through it: An example of sustainable traditional irrigation in Western Cape Province,South Africa     

H. A. P. Smit  J. A. Jacobs 《GeoJournal》2004,61(2):191-196

Water and water related matters are important issues in water scarce countries like the Republic of South Africa. This is especially true for the agricultural sector that relies heavily on the availability of water for irrigation to ensure a secure food supply. In South Africa, present day irrigation projects rely on government subsidies and are usually large undertakings beyond the reach of individuals or small communities. The sustainability of such large irrigation projects is still a matter of debate. A 100 years ago a different set of rules applied. Irrigation could only be achieved by hand-dug furrows that supplied water in relatively small quantities to small farming communities. This paper investigated such a small community, the Leeukloof farming community in the Western Cape Province of the Republic of South Africa. For the past 93 years this community has maintained a furrow that supplies water not only to farms bordering the Perdeberg River, which supplies the furrow with water, but also to farms not bordering the river. The authors try to reconstruct the changes in agricultural practices brought about by the furrow, methods of water extraction during each phase, as well as the development and role of the furrow system. The perception by the community of the necessity of this method of water extraction from the river system is also investigated. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The environmental planning and management approach towards the development and management of the Osun natural spring project,Ibadan, Nigeria     

S. O. Asamu 《GeoJournal》2004,61(2):183-189

There is a general shortage of potable water in Nigeria, partly through the lack of natural provision and partly because of rapid urban growth that has largely been unplanned. The paper describes the recent redevelopment of a public water facility in a run-down area of Ibadan which is part of the Sustainable Ibadan Project. Despite funding from national and international bodies, the development is strongly based at community level. The local inhabitants feel they have control over their own water supply through their representatives on the various planning and managing committees. This aims to reduce vandalism and to increase pride and involvement in the community. The project is a pilot for other projects around Ibadan, some of which have begun and others are being planned. This paper describes the administrative structures and management principles that have been employed. It forcefully advocates community-based planning and management which respects both the environment and the water-users, and involves a major “bottom-up” element. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Geodynamic Information in Peridotite Petrology   总被引：12，自引：1，他引：12  

HERZBERG  CLAUDE 《Journal of Petrology》2004,45(12):2507-2530

Systematic differences are observed in the petrology and majorelement geochemistry of natural peridotite samples from thesea floor near oceanic ridges and subduction zones, the mantlesection of ophiolites, massif peridotites, and xenoliths ofcratonic mantle in kimberlite. Some of these differences reflectvariable temperature and pressure conditions of melt extraction,and these have been calibrated by a parameterization of experimentaldata on fertile mantle peridotite. Abyssal peridotites are examplesof cold residues produced at oceanic ridges. High-MgO peridotitesfrom the Ronda massif are examples of hot residues producedin a plume. Most peridotites from subduction zones and ophiolitesare too enriched in SiO₂ and too depleted in Al₂O₃ to be residues,and were produced by melt–rock reaction of a precursorprotolith. Peridotite xenoliths from the Japan, Cascades andChile–Patagonian back-arcs are possible examples of arcprecursors, and they have the characteristics of hot residues.Opx-rich cratonic mantle is similar to subduction zone peridotites,but there are important differences in FeO_T. Opx-poor xenolithsof cratonic mantle were hot residues of primary magmas with16–20% MgO, and they may have formed in either ancientplumes or hot ridges. Cratonic mantle was not produced as aresidue of Archean komatiites. KEY WORDS: peridotite; residues; fractional melting; abyssal; cratonic mantle; subduction zone; ophiolite; potential temperature; plumes; hot ridges  相似文献