我国金伯利岩含金性试验研究--以辽宁瓦房店50号岩管为例

一般认为原生或伴生金矿床在成因上与中酸性火成岩有关.文章通过我国金伯利岩型金刚石矿床伴生金的试验研究,确定该类型伴生金矿与超基性火成岩有关.金伯利岩中个别样品w(Au)=0.46×10-6,金刚石选矿尾矿及其重选精矿金的质量分数均较高,具有一定的学术研究价值和开发利用前景.     

Models-3空气质量模式对兰州市污染物输送的模拟

较详细地介绍了美国环保总局的第三代空气质量模式系统Models-3的特点,并且针对兰州市冬季采暖期污染严重的特点,选取2002年12月份的个例,将兰州市最新的大气污染源资料加入模式中．对模式进行调试并检验了该模式对兰州污染的模拟性能。从模式对SO2,NO2和O3等几种大气污染物浓度的模拟结果与监测资料对比分析,表明该模式系统较好地模拟出了SO2,NO2的空间分布格局,模拟结果与监测结果比较吻合,而且模式模拟的污染物浓度场比较均匀;模式模拟的O3的日变化规律与资料分析结论基本一致,也符合O3的生成机理。因此该模式系统对于复杂地形条件下的城市污染物输送具有一定的模拟能力。     

A study on the seismic behavior of a retrofitted building based on nonlinear static and dynamic analyses

This study describes the seismic performance of an existing five storey reinforced concrete building which represents the typical properties of low-rise non-ductile buildings in Turkey. The effectiveness of shear walls and the steel bracings in retrofitting the building was examined through nonlinear static and dynamic analyses. By using the nonlinear static analysis, retrofitted buildings seismic performances under lateral seismic load were compared with each other. Moreover, the performance points and response levels of the existing and retrofitting cases were determined by way of the capacity-spectrum method described in ATC-40 (1996). For the nonlinear dynamic analysis the records were selected torepresent wide ranges of duration and frequency content. Considering the change in the stiffness and the energy dissipation capacities, the performance of the existing and retrofitted buildings were evaluated in terms of story drifts and damage states. It was found that each earthquake record exhibited its own peculiarities, dictated by frequency content, duration, sequence of peaks and their amplitude. The seismic performance of retrofitted buildings resulted in lower displacements and higher energy dissipation capacity depending mainly on the properties of the ground motions and the retrofitting strategies. Moreover, severe structural damage (irreparable or collapse) was observed for the existing building. However, buildings with retrofit alternatives exhibited lower damage levels changing from no damage to irreparable damage states.     

An operational modal analysis method in frequency and spatial domain

A frequency and spatial domain decomposition method （FSDD） for operational modal analysis （OMA） is presented in this paper, which is an extension of the complex mode indicator function （CMIF） method for experimental modal analysis （EMA）. The theoretical background of the FSDD method is clarified, Singular value decomposition is adopted to separate the signal space from the noise space. Finally, an enhanced power spectrum density （PSD） is proposed to obtain more accurate modal parameters by curve fitting in the frequency domain. Moreover, a simulation case and an application case are used to validate this method.     

尚未完成的地质年代表--第四纪悬而未决的前程

第四纪是以气候变化、人类出现和现生生物物种占优势为特征的最新地质时期。第四纪的地层多以松散沉积物为主,是人类赖以生存居住的主要场所。鉴于第四纪研究对地质学,地球系统科学和全球变化科学的贡献,近几十年来学术界和公众对其产生极大兴趣和更加重视。为了回应2 0 0 4年春国际地层委员会提出的“国际地层表”( 2 0 0 4 ) ,详细地介绍了国际第四纪联合会为争取第四纪在地质年表中的合理地位所作的努力以及目前争论的结果:今年比利时最终定论。呼吁我国广大的第四纪工作者积极加入到支持国际第四纪联合会保留第四系作为独立地层单元的行列中。同时简略地介绍了第四纪(系)术语的来由,国内外关于第四纪下限研究的历史和现状     

Erratum to: Geochemical and environmental magnetic characteristics of high arsenic aquifer sediments from Datong Basin,northern China

Geochemical and environmental magnetic studies were carried out to identify the effect of iron oxyhydroxides on arsenic mobilization in high arsenic aquifer system. Using high arsenic sediment samples from two boreholes, specifically drilled for this study, chemical composition and magnetic properties including magnetic susceptibility, saturation remnant magnetization, and isothermal remnant magnetization were measured. Results of correlation analysis of element contents show that arsenic and iron are closely associated with each other (r ² = 0.40, α = 0.05, n = 21). In contrast, the correlation of phosphorus with iron (r = 0.11, α = 0.05, n = 21) and arsenic (r ² = 0.18, α = 0.05, n = 21) was poor, which might result from competitive adsorption of phosphorus and arsenic on the surface of Fe-oxyhydroxides. The high correlation coefficients between arsenic contents and magnetic parameters suggest that the ferrimagnetic minerals including maghemite and hematite are the dominant carrier of arsenic in aquifer sediments. The results of sequential extraction experiments also revealed the association of arsenic with reducible iron oxides, such as maghemite and hematite in aquifer sediments. Therefore, under reducing conditions, reductive dissolution and desorption of arsenic from Fe-oxyhydroxides into the aqueous phase should be the dominant geochemical processes for its enrichment in groundwater at Datong. An erratum to this article can be found at     

Geochemistry and mineralogy of shallow alluvial aquifers in Daudkandi upazila in the Meghna flood plain, Bangladesh

The shallow alluvial aquifers of the delta plains and flood plains of Bangladesh, comprises about 70% of total land area are mostly affected by elevated concentrations of arsenic (As) in groundwater exposing a population of more than 35 million to As toxicity. Geochemical studies of shallow alluvial aquifer in the Meghna flood plain show that the uppermost yellowish grey sediment is low in As (1.03 mg/kg) compared to the lower dark grey to black sediment (5.24 mg/kg) rich in mica and organic matter. Sequential extraction data show that solid phase As bound to poorly crystalline and amorphous metal (Fe, Mn, Al)-oxyhydroxides is dominant in the grey to dark grey sediment and reaches its maximum level (3.05 mg/kg) in the mica rich layers. Amount of As bound to sulphides and organic matter also peaks in the dark grey to black sediment. Vertical distributions of major elements determined by X-ray fluorescence (XRF) show that iron (Fe₂O₃), aluminum (Al₂O₃) and manganese (MnO) follow the general trend of distribution of As in the sediments. Concentrations of As, Mn, Fe, HCO₃ ⁻, SO₄ ²⁻ and NO₃ ⁻ in groundwater reflect the redox status of the aquifer and are consistent with solid phase geochemistry. Mineralogical analysis by X-ray diffraction (XRD) and scanning electron microscopy (SEM) fitted with energy dispersive X-ray spectrometer (EDS) revealed dominance of crystalline iron oxides and hydroxides like magnetite, hematite and goethite in the oxidised yellowish grey sediment. Amorphous Fe-oxyhydroxides identified as grain coating in the mica and organic matter rich sediment suggests weathering of biotite is playing a critical role as the source of Fe(III)-oxyhydroxides which in turn act as sink for As. Presence of authigenic pyrite in the dark grey sediment indicates active reduction in the aquifer.     

Organic tracers in sediments from the coastal zone of Ras Abu el-Darag,Gulf of Suez

Sediment samples from the coastal zone of the Gulf of Suez contain a variety of organic compounds from anthropogenic and natural sources. A total of 12 surface samples of bottom sediments were collected with an Ekman grab sampler along an off-shore transect south of Ras Abu el-Darag. The samples were extracted with a mixture of dichloromethane and methanol (3:1 v/v) after drying and sieving through 250 μm mesh. The extracts were derivatized and analyzed by gas chromatography–mass spectrometry in order to characterize the chemical composition and sources of the organic components. Marine with minor terrestrial biota were the major natural sources of organic tracers and included n-alkanoic acids, sterols and saccharides (5.7–76.7%). Anthropogenic sources, from petroleum related activities, detergent usage for spill cleaning and littering, are indicated by the presence of n-alkanes with carbon preference index ≤1.0, hopanes, steranes, unresolved complex mixture of branched and cyclic hydrocarbons, alkyl nitriles, alkamides and plasticizers. Their total relative concentrations ranged from 23.3 to 97.3% of the total extracts. Petroleum residues from natural seepage may also be part of these hydrocarbons. The levels of anthropogenic inputs decrease from about 94% in coastal zone sediments to about 20% in sediments from the reef front.     

塔北地区构造和演化特征及其对油气成藏的控制

塔北隆起为塔里木盆地最富有油气的构造单元之一,其纵向上可分为中新生界和古生界两大构造层,上下特征有较大的差异性:古生界受到六条基底逆断层及其伴生断裂控制,构造格局可以划分为"四隆两凹"的构造单元:英买力低凸起、轮台低凸起、哈拉哈塘凹陷、轮南低凸起、草湖凹陷以及库尔勒鼻隆,该格局长期继承性发育,并逐层遭受剥蚀形成整个塔北残余古隆起,其上构造圈闭十分发育,同时由于暴露时间长,碳酸盐岩储层非常发育;中新生界整体上表现为南高北低的北倾斜坡形态,受到下伏古生界断层的后期活化影响,发育局部圈闭。塔北当前的构造格局在演化过程中主要形成于海西期,后期变化较小。研究表明,塔北地区构造演化大致经历了三大阶段:晚加里东-早海西期的稳定抬升剥蚀期,塔北在南倾的大斜坡背景上形成了北东-南西走向的轮南大型背斜,英买力低凸起初具雏形;晚海西-印支期的挤压抬升期,塔北隆起在原背景之上继承发展;燕山-喜山期为调整定型期,形成现今塔北地区构造格局。整体古生界构造格局形成早,稳定时间长,是库车油气和满加尔油气的长期指向区,控制了塔北地区油气分布,而多期的构造演化则控制了塔北地区油气藏不同时期的破坏和形成,也造就了目前塔北地区同时存在沥青、稠油、轻质油和天然气。     

青海东昆仑东段金矿区地层含矿性分析

近年来勘查成果表明,青海东昆仑东段是一个以金为主的成矿聚集区,各矿区含矿层位不尽相同。通过对不同的含矿地层和岩体地球化学微量元素分析,认为地层并不能提供金矿成矿物质的来源。区域变质作用造成了金的活化迁移,后期的岩浆热液作用对金的富集具有重要的作用。