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1.
CSAMT 法在辽西康杖子区深部探矿中的应用 总被引：5，自引：0，他引：5
可控源音频大地电磁法(CSAMT)具有探测深度大、横向分辨率高、抗干扰能力强的特点,在深部找矿勘探中有着重要的指导意义。肖家营子铜钼矿床是辽西地区一个大型矽卡岩型金属矿床,大部分矿体是隐伏矿体,矿区外围的康杖子区与本区有相似的成矿地质环境,成矿地质条件优越.矿体与围岩电性差异明显,通过应用CSAMT,矿体具有低电阻特点,根据成果推断解释,对深部有利成矿部位进行了钻探验证,取得了理想的探矿效果,在矿区外围取得第二深度空间找矿重大突破。 相似文献
2.
硫代砷是富硫化物地下水中砷的重要形态,对环境和人类健康有潜在威胁。目前硫代砷研究程度尚低,本次主要针对国内外地下水（地热水）中硫代砷的存在形态,水文—生物—环境地球化学过程,样品保存,定量检测方法等方面进行研究。结论如下:pH, 氧化还原电位,硫化物含量和微生物作用等是影响地下水中硫代砷稳定存在和形态分布的重要因素。含铁矿物能与水中的硫代砷形成配位键对其进行吸附,吸附性普遍弱于（亚）砷酸盐,因此,地下水中硫代砷可能表现出更强的迁移性。用于硫代砷检测的自然水样在采集中可采取过滤,速冻,厌氧和低温短期保存的操作流程,以减缓该形态的转化甚至消失。色谱联用ICP-MS系统可用于自然水样中硫代砷的分离定量检测,紫外—可见分光光度法和X射线吸收光谱法在不同场景下也可对硫代砷进行定量和表征分析。地热水和浅层地下水中均可能存在硫代砷,由于水样中硫代砷的不稳定性,室内检测和分析难以准确反映现场过程,因此,野外样品保存技术和现场检测方法的更新可能在未来有更大研究空间,值得进一步探索。 相似文献
3.
Trends in landslide occurrence in Nepal 总被引：2，自引：0，他引：2
David N. Petley Gareth J. Hearn Andrew Hart Nicholas J. Rosser Stuart A. Dunning Katie Oven Wishart A. Mitchell 《Natural Hazards》2007,43(1):23-44
Nepal is a mountainous, less developed kingdom that straddles the boundary between the Indian and Himalayan tectonic plates.
In Nepal, landslides represent a major constraint on development, causing high levels of economic loss and substantial numbers
of fatalities each year. There is a general consensus that the impacts of landslides in countries such as Nepal are increasing
with time, but until now there has been little or no quantitative data to support this view, or to explain the causes of the
increases. In this paper, a database of landslide fatalities in Nepal has been compiled and analysed for the period 1978–2005.
The database suggests that there is a high level of variability in the occurrence of landslides from year to year, but that
the overall trend is upward. Analyses of the trends in the data suggest that there is a cyclicity in the occurrence of landslide
fatalities that strongly mirrors the cyclicity observed in the SW (summer) monsoon in South Asia. Perhaps surprisingly the
relationship is inverse, but this is explained through an inverse relationship between monsoon strength and the amount of
precipitation in the Hill District areas of Nepal. It is also clear that in recent years the number of fatalities has increased
dramatically over and above the effects of the monsoon cycle. Three explanations are explored for this: land-use change, the
effects of the ongoing civil war in Nepal, and road building. It is concluded that a major component of the generally upward
trend in landslide impact probably results from the rural road-building programme, and its attendant changes to physical and
natural systems. 相似文献
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5.
2010年,美国铀矿总共施工7 209个钻孔,总进尺1 493 520 m;生产铀1 628.55 t;铀矿业总支出费用为2.773亿美元,其中铀矿地勘费支出为3 450万美元,占铀矿业总费用的12.44%。铀矿地勘钻探费用为4 460万美元,占铀矿业总费用的16.08%。 相似文献
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Radon is a radioactive gas emanating naturally from uranium rich granites and shales. It may be emitted from the ground surface into the atmosphere as a gas, or it may be dissolved into stream water and transported over distance. The levels of radon gas in soils at ground surface depend on a number of factors relating to the source of the gas and to its transmission. Igneous rocks contain the highest mean concentrations of radium and uranium. The depth of cover is relevant also. Surveys over the years by the National Radiological Protection Board (NRPB) and others have indicated that the highest concentrations in the United Kingdom occur in Cornwall, Devon and northeast Scotland. However, recent reports have indicated that high concentrations of the gas may be detected in small pockets in counties outside of those considered at high risk. This survey relates to a series of measurements taken in and around Darlington, County Durham. The results showed the presence of small areas with strong concentrations of radon in soil gas, but only minor levels of dissolved gas in stream waters. 相似文献
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河口港湾沉积物中的(137)Cs剖面及其沉积学意义 总被引：15，自引：2，他引：15
本文通过对采自海南岛洋浦港?福建厦门外港?浙江象山港三个河口港湾的六个沉积柱样的137Cs分析,分别用137Cs剖面的最大峰值层及137Cs剖面的起始值层位估算了该六个站位的现代沉积速率,结果表明:在河口港湾沉积环境条件下,用137Cs剖面来估算沉积物的平均沉积速率是可行的,由137Cs最大值法,这六个站位的平均沉积速率分别为1.14cm/a?1.56cm/a?0.82cm/a?0.75cm/a?1.26cm/a?1.66cm/a,由137Cs最大值法得出的平均沉积速率其精确度与可信度要好于137Cs起始值得出的平均沉积速率?与210Pb法所得的结果符合的很好?137Cs起始值层位与预期值偏离的大小可以为我们提供有关该站位沉积环境?扰动作用强弱的信息?在应用137Cs剖面估算沉积速率时,还要注意沉积结构变化的影响? 相似文献
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南秦岭金矿成矿的几点认识于学元，郑作平（中国科学院广州地球化学研究所，广州５１０６４０）关键词金矿床，成矿带，南秦岭秦岭地质构造极其复杂，是一个巨大的缔向构造带，也是我国重要的有色金属矿产基地。近几年来，随着对秦岭地区地质研究强度的加强，在贵重金属找... 相似文献
12.
Using average nutritive values of food actually consumed by individuals, this paper identifies regional concentration of hunger (food poverty) and its changes over time in rural India. There is clearly a heavy concentration of hunger in the coastal states of India, with few exceptions, which has persisted over time. Hunger has declined in about half the states of India but has increased in the remaining half. Unfortunately, it seems to have increased in the states that are relatively prosperous and are surplus producers of food. Hence, increased production of food, though important, does not necessarily reduce hunger. A redeeming conclusion of the study is that there has been a general improvement in the quality of food intake, particularly in the states where food poverty has declined. 相似文献
13.
《International Geology Review》2012,54(9):1388-1395
A consistent, relatively rapid decrease in FeS molecular content of sphalerites at decreasing depth is recognizable in upper parts of this structurally controlled Pb-Zn ore deposit, as an expression of tectonic calm and continuity of the productive stages of the mineralization. Elsewhere, in the depths, abrupt changes in quantity of isomorphous iron in sphalerites, within a relatively short depth-span, signify intensive movements during deposition of the ore. Wherever the structures are bent and healed by early quartz sufficiently to retard circulation of the solutions and to promote their cooling, variations in the FeS content of sphalerite at different depths may be related to thermal “knickpoints” of the ascending solutions. Nonetheless, FeS molecular content of sphalerites is no clue to the temperature of their crystallization. There is no relationship between the depth at which sphalerite was formed and the isomorphous Cd or Mn in crystal structures of the mineral. — V.P. Sokoloff. 相似文献
14.
This article discusses the involvement of older women and men in voluntary work in rural communities in the Netherlands. Gender,
ageing and civil society form the core concepts in the article. Politicians and policy makers in the Netherlands are worried
about the perceived decline of civil society and about the consequences of this decline for specific categories of older women
in terms of well-being and social exclusion. The paper presents the results of two surveys of involvement of older women and
men in civic organisations, voluntary work and local actions. The surveys indicate high levels of involvement of both women
and men. No gender differences are found in activity level. However, the data demonstrate the gendered nature of civil society.
Women are more engaged in informal voluntary work and informal local actions, while men are more active in formal organisations
and functions. This gender segmentation is not absolute, however. Many older women and men transgress the traditional feminine–masculine
boundaries. The surveys highlight the involvement of women and men in rural communities, but indicate lower activity levels
in urban areas. 相似文献
15.
Conflicts arise increasingly in Tanzania which involve claims in land located in conservation areas. These conflicts arise,
in many cases, between members of the local communities and the state authorities in charge of the conservation areas. They
concern customary land rights both of pastoral and of agricultural communities, a topic which also touches upon their identities.
The article investigates the legal dimension of these disputes by discussing the law governing conservation areas in the wider
context of land tenure legislation. Within this context, the legal framework of conservation areas is discussed from both
historical and contemporary perspectives. Nature conservation must respect the needs of the local population affected. It
is therefore argued that concepts of community-based conservation should be developed further to work towards the goal of
integrating nature conservation and the sustainable use of natural resources.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
This paper outlines the recent advances in geochemical exploration in China.The Regional Geochemistry—National Reconnaissance (RGNR) Project first proposed in 1978, continues to be the focus of geochemical exploration activities in China. Several rapid quantitative multi-element analysis systems using conventional equipment available in most Chinese geological laboratories, have been developed. Eight Geochemical Standard Reference Samples of Drainage Sediments were prepared. Large-scale orientation or pilot surveys are being carried out by nearly 2/3 of the provincial geological bureaus in China. Methods of regional and follow up surveys for high and cold mountainous terrain have been worked out.Special attention has been given to the improvement and application of mercury vapour detection techniques. A new sampler was used to enhance anomalous values. A new Zeeman effect mercury detector was constructed and tested in routine analysis of mercury. Experiments of the application of soil gas mercury survey in petroleum and uranium prospecting are briefly described.Some examples of recent geochemical success in China are given. 相似文献
17.
Compositional zonation in garnets in peridotite xenoliths 总被引：1，自引：0，他引：1
Garnets in 42 peridotite xenoliths, most from southern Africa, have been analyzed by electron probe to seek correlations between compositional zonation and rock history. Xenoliths have been placed into the following 6 groups, based primarily upon zonation in garnet: I (12 rocks)-zonation dominated by enrichment of Ti and other incompatible elements in garnet rims; II (10 rocks)-garnet nearly homogeneous; III (8 rocks)-rims depleted in Cr, with little or no related zonation of Ti; IV (3 rocks)-slight Ti zonation sympathetic to that of Cr; V (3 rocks)-garnet rims depleted or enriched in Cr, and chromite included in garnet; VI (6 rocks)-garnets with other characteristics. Element partitioning between olivine, pyroxene, and garnet rims generally is consistent with the assumption of equilibrium before eruption. Although one analyzed rock contains olivine and pyroxene that may have non-equilibrated oxygen isotopes, no corresponding departures from chemical equilibrium were noted. Causes of zoning include melt infiltration and changes in temperature and pressure. Zonation was caused or heavily influenced by melt infiltration in garnets of Group I. In Groups III, IV, and V, most compositional gradients in garnets are attributed to changes in temperature, pressure, or both, and gradients of Cr are characteristic. There are no simple relationships among wt% Cr2O3 in garnet, calculated temperature, and the presence of compositional gradients. Rather, garnets nearly homogeneous in Cr are present in rocks with calculated equilibration temperatures that span the range 800–1500 °C. Although the most prominent Cr gradients are found in relatively Cr-rich garnets of rocks for which calculated temperatures are below 1050 °C, gradients are well-defined in a Group IV rock with T1300 °C. The variety of Cr gradients in garnets erupted from a range of temperatures indicates that the zonations record diverse histories. Petrologic histories have been investigated by simulated cooling of model rock compositions in the system CaO–MgO–Al2O3–SiO2–Cr2O3. Proportions and compositions of pyroxene and garnet were calculated as functions of P and T. The most common pattern of zonation in Groups III and IV, a decrease of less than 1 wt% Cr2O3 core-to-rim, can be simulated by cooling of less than 200 °C or pressure decreases of less than 1 GPa. The preservation of growth zonation in garnets with calculated temperatures near 1300 °C implies that these garnets grew within a geologically short time before eruption, probably in response to fast cooling after crystallization of a small intrusion nearby. Progress in interpreting garnet zonations in part will depend upon determinations of diffusion rates for Cr. Zonation formed by diffusion within garnet cannot always be distinguished from that formed by growth, but Ca–Cr correlations unlike those typical of peridotite suite garnets may document diffusion. 相似文献
18.
浙闽泥质区是全新世高海平面以来沉积物的汇。受东亚季风影响,浙闽沿岸流和台湾暖流具有季节性变化,长江口"夏储冬输"的沉积物输运模式对东海内陆架泥质区的形成有关键作用。浙闽泥质区的潜在物源主要有长江、浙闽河流以及台湾西部山地河流,以长江物质为主。黏土矿物、稀土元素、Sr-Nd同位素、环境磁学等方法是物源研究的重要手段。长江物质以伊利石为主,蒙脱石含量较少,高岭石和绿泥石含量中等;而台湾物质以伊利石和绿泥石为主,没有蒙脱石。磁黄铁矿是台湾河流沉积物特有的磁性矿物,可作为大陆河流与台湾河流物源识别的指标。泥质区位于东亚季风区,受低纬热带过程和高纬大气环流的影响,气候变化具有波动性。沉积物敏感粒级反演的东亚冬季风（EAWM）只记录了泥质区形成以来的气候变化,不能代表整个全新世。受台湾暖流和浙闽沿岸流的双重影响,敏感粒级作为EAWM演化的指标需进一步深入研究。 相似文献
19.
Dr. Zoltan De Cserna 《International Journal of Earth Sciences》1960,50(1):595-605
The evolution of the border region of part or all of a craton, on the basis of geological data gathered from Mexico, may best be described in terms of geotectonic cycles. These consist, in chronological order, of (1) an orthogeosynclinal phase (eu- and miogeosynclines) with or without initial magmatic activity, (2) an anatexitic phase consisting of batholith emplacement with attendant regional metamorphism in the eugeosyncline and deposition of a clastic or flysch wedge over the miogeosyncline, (3) an orogenic phase consisting principally of the folding and thrusting of the sediments of the miogeosyncline together with the clastic or flysch wedge against the foreland, and (4) a taphrogenic or block-faulting phase accompanied by (a) accumulation of post-orogenic debris or molasse, (b) subsequent magmatic activity consisting largely of igneous extrusions with fewer intrusions, and (c) final magmatic activity consisting of igneous extrusions. A region that has gone through the above phases of a geotectonic cycle may be termed a structural belt. In the post-Precambrian geologic history of Mexico, three geotectonic cycles are recognized: one occurred along the Pacific border of Mexico between Cambrian and middle Jurassic (?) time (Jaliscoan geotectonic cycle), the second occurred along the present Gulf of Mexico border of the country at the same time (Huastecan geotectonic cycle), and the third occurred over the entire country from the United States border to the Guatemalan border between Late Jurassic and Pliocene time (Mexican geotectonic cycle). The early Mesozoic clastic rocks in northwestern Mexico may signify a fourth geotectonic cycle in that region. In the three recognized geotectonic cycles, however, the geologic record shows only two orogenic phases, one of which occurred in late Paleozoic time in an arcuate belt along the eastern side of Mexico (Coahuilan orogeny), and the other in early Tertiary time in a belt traversing central Mexico from the United States border to the Guatemalan border (Hidalgoan orogeny). 相似文献
20.
Gold abundance in granitic rocks of different geological periods in southern China has been estimated. A review of the quantitative data available indicates that unaltered granitic rocks have a rather restricted range in gold content, rarely exceeding 4 ppb and generally ranging from 1.4 to 3.3 ppb. The mean gold content tends to decrease from basic to acidic granitoids. This tendency suggests that gold isnot concentrated in the residual silicate meltduring the formation of granitic rocks. It is necessary to establish the background values of gold for various rock types although it seems that gold abundance data for the granitic rocks of southern China can necessarily provide any geochemical clues or guides to areas favorable or unfavorable for gold mineralization. 相似文献