Geochemical dispersion of lead and zinc around a gossan in a carbonate environment at Heure (Belgium)

Samples of a brecciated sulphide vein (marcasite, sphalerite and scarce galena, in a calcite gangue), and its gossan, were collectet from bore holes. The gossan consists dominantly of goethite alternating with lepidocrocite and hydrohematite in a type of boxwork structure. Lead and manganese oxides are present. The gossan contains about 0.6% zinc and 0.2% lead. Sequential selective extractions and electron microprobe analyses were carried out. Soils with anomalous values in lead and zinc lying adjacent to the gossan contain fragments of ferruginous material which possess dimensions ranging from hundreds of microns to several centimeters. The textures, mineralogy and trace element contents of the fragments resemble those of limonites from the gossan. Mineralogical and selective analyses on the gossan and the soil materials show mineralogical and geochemical analogies. Lead and zinc anomalies can be explained partly by the occurrence of limonitic microfragments in the anomalous soils. The origin of these fragments is related to the disaggregation of the gossan. Already evoked by others authors for mainly non-carbonate environments, the results weight to the hypothesis that the dispersion of lead and zinc is partly mechanical.     

Selective chemical extraction of Cu from selected mineral and soil samples: enhancement of Cu geochemical anomalies in Southern Portugal

The study described herein concerns the application of selective chemical extractions on metal-bearing minerals and soils to geochemical exploration. Specifically, the study aims at the detection of anomalous soils in the vicinity of two mineralized zones in Southern Portugal.A kinetic study of the selectivity of partial chemical extractions applied to Cu minerals has been carried out in order to establish a systematic procedure (reagents, extraction plateau, etc.) which could be recommended for soils of the two study zones. It is shown that: (1) NH₄ acetate dissolves malachite, azurite and cuprite completely and chrysocolla, conicalcite and atacamite only partially; (2) hydroxylamine hydrochloride dissolves chrysocolla and conicalcite only partially; (3) H₂O₂ dissolves chalcopyrite only partially; (4) NH₄ oxalate (U.V.) dissolves conicalcite and atacamite only partially; (5) mixed-acid attack dissolves residual chalcopyrite, chrysocolla, atacamite and conicalcite.A total of 740 soil samples were collected from the Salgadinho and Tinoca areas. The Cu mineralization in the Salgadinho area is situated in an Upper-Devonian Volcanic-Siliceous Complex. The weathering products of the mineralization are mainly amorphous iron oxides, goethite and hematite. The Cu mineralization in Tinoca area is located in the Arronches-Campo Maior belt, where stratiform Cu mineralization is found. The weathering products of the mineralization are mainly malachite, amorphous iron oxides, goethite and hematite.In order to identify the Cu-bearing phases and the extraction plateau, the −80 mesh fraction of two soil samples was submitted to an extraction procedure using the following reagents in sequence: NH₄ acetate, hydroxylamine hydrochloride, NH₄ oxalate (dark), NH₄ oxalate (U.V.) and finally strong acids.In soils from the Salgadinho and Tinoca areas, the use of NH₄ oxalate (U.V.) in single dissolution which would incorporate those phases dissolved by NH₄ acetate and NH₄ oxalate (dark), gives the broadest anomalous surface and higher contrast for Cu than acid digestion. The analysis of NH₄ oxalate (U.V.) extractions, instead of acid digestion, can thus be recommended for both areas.     

Prediction of phytoavailability of trace metals to plants: Comparison between chemical extractions and soil-grown radish

One of the major routes of human exposure to toxic metals is the consumption of vegetables grown on contaminated soils. Radishes were grown in three different soils (kitchen garden, agricultural and industrial soils), presenting various contamination levels. A sequential extraction procedure was compared with EDTA and HCl simple extractions methods in order to predict the metals phytoavailabilty to radish. The analysis of the results shows that the simple HCl and sequential chemical extractions bring complementary results, since HCl is correlated in the phytoavailability of Cd, Mn and Zn, whereas the sequential extraction is correlated in the phytoavailability of Cr, Fe, Mn, Ni. EDTA simple extraction brings here less interesting results than the two other tested extractions.     

Lead-arsenic soil geochemical study as an exploration guide over the Killik volcanogenic massive sulfide deposit, Northeastern Turkey

A mountainous terrain, the eastern Pontide tectonic belt, located in northeastern Turkey, contains more than 60 known volcanogenic massive sulfide (VMS) deposits that differ in reserves (0.1–30 million tonnes) and grades. Soil geochemistry is conventionally used in exploration programs to discover concealed VMS deposits in the region. In the present study, Pb and As element pair were used as pathfinder elements to investigate the relationship of their anomalies to a completely delineated ore deposit (Killik VMS deposit) in an orientation survey that served as a natural physical model. Two hundred forty soil samples were analyzed in the present study. The two elements, which represent the opposite ends of the mobility range, revealed high contrast and overlapped each other at the location of the ore deposit due to enhancement of the anomalies by hydromorphic dispersion, which is an indication that soil samples would produce reliable results. The successful delineation of the deposit is remarkable considering the rough topography and the climatic limitations. Previously the extremely moist and temperate climate was thought to cause excessive leaching of the trace element pathfinders from the ore deposits to produce extensive anomalies usually extending away from the mineralization thus, leading to erroneous results and/or extensive anomalous areas. But the present research has shown that the method can be used effectively if the sampling and data evaluation is carefully conducted.     

Selective extraction techniques in exploration for volcanogenic sulphide deposits, Eastern Black Sea region, Turkey

Selective extraction techniques employing 0.05 M EDTA, 1 M hydroxylamine hydrochloride (Hxl) in acetic acid and 0.157 M ammonium oxalate in oxalic acid were used to assess the mode of occurrence of the trace elements in the various geochemical sample media and to increase the anomaly contrast over the concealed massive ore bodies in the the Eastern Black Sea region of Turkey.In hematitized pumice tuffs, an exhalate horizon overlying the Madenköy massive sulphide ore body, the trace elements such as As, Cu, Zn, Pb and Mo are partly associated with sulphides and partly occur in clays, and Fe- and Mn-oxides.The extraction data on stream sediments suggest that a hot nitric acid attack is the best digestion procedure for detecting mechanical dispersion trains in regional geochemical programmes. Comparison of the extractabilities of metals in soils from mineralized areas with those from the background Sirtköy soils by the different extraction procedures demonstrates that EDTA, and to lesser extent Hxl are the best extraction procedures for increasing the anomaly/background ratio. These two extraction procedures were found to also enhance Zn and Pb anomalies over the cover rocks of the Madenköy massive ore body relative to the largely exposed stockwork-impregnation zones.Among the EDTA, Hxl and ammonium oxalate extractions, only the last procedure extracted considerable amounts of As from the soil samples. Vapor-phase analysis suggests that mercury occurs mainly in sulphide form which is leachable only by ammonium oxalate solution that also leaches adsorbed mercury. The EDTA and the Hxl solutions only extracted adsorbed mercury. These three extractants have no effect on either mercuric oxide or mercuric sulphate. Arsenic, a very useful pathfinder in this region, can only be partly extracted from the pumice tuff and soil samples by ammonium oxalate solution.     

物探技术在布敦乌拉隐伏矿产勘查中的应用效果

内蒙古西乌珠穆沁旗布敦乌拉矿区多为第四系覆盖。在该矿区多金属勘查中,依据土壤地球化学圈定的矿化异常布置激电中梯测量,圈定1处激发极化率异常区,长度约890m,宽度约520m,位于已知断层F 1与推断断层F 2之间。采用可控源音频大地电磁测深剖面对该激电异常进行探测,解释视充电率多峰异常与反演电阻率高低跳跃对应区域为矿致异常区。通过钻探验证,发现银多金属矿床资源储量523.93万t,取得了良好的地质找矿效果。     

PGE exploration in the Wadi Amarah complex,southwestern Arabian Shield

A stream sediment survey targeting PGE and their pathfinders was carried out at a gabbro/pyroxenite complex in Wadi Amarah in the SW Arabian Shield. Twenty-nine stream sediment samples were collected from wadi channels and analyzed for PGE and base metals. None of the samples contained detectable PGE except for WAS-3 and WAS-27 which returned values above 70 ppb of combined Pt and Pd; these two locations are also anomalous for Au. A follow-up survey was conducted to further investigate the anomalies at these locations. A total of 48 soil and rock samples were collected from the two anomalous localities. Unlike the initial survey, most samples contained detectable PGE and Au albeit not as high as the original anomalies. Factor analysis of the results from the initial survey returned five main factors, with the first four reflecting the effects of mineral detritus as well as adsorption onto Fe–Mn oxyhydroxides; however, the last factor is loaded only for Cu and Ni and is therefore considered an ore factor indicating the presence of Cu–Ni sulphides. Another five factors were obtained from the follow-up survey, and as was the case in the initial survey, the first four factors are detrital/adsorption-related, while factor 5 has high loadings for only Pd and Pt and is therefore interpreted as a PGE ore factor. These findings reveal different modes of dispersion of PGE and base metals in the secondary environment and, more importantly, demonstrate the effectiveness of factor analysis in detecting even faint anomalies from disseminated mineralization.     

Application of the BCR sequential extraction scheme to dredged pond sediments contaminated by Pb–Zn mining: A combined geochemical and mineralogical approach

The modified BCR sequential extraction procedure [Rauret, G., López-Sanchez, J., Sauquillo, A., Rubio, R., Davidson, C., Ure, A., Quevauviller, Ph., 1999. Improvement of the BCR three step sequential extraction procedure prior to certification of new soil and sediment reference materials. J. Environ. Monit. 1, 57–60.] was applied to 4 sediments from a mine tailing pond in La Calamine (East-Belgium). The results showed a very different behaviour of different samples towards the same extraction scheme. In samples with an elevated acid neutralizing capacity, a significant increase in the pH of the extracts was measured after the first two extraction steps. Other artefacts, such as readsorption of metals and precipitation could be deduced by comparing X-ray diffraction patterns after different extraction steps. For example, anglesite was effectively dissolved during the acid extraction step (step 1) but relatively low Pb concentrations were measured in the CH₃COOH extract because of the readsorption of Pb. Mineralogical analysis of the sediments after each extraction step also indicated the incomplete oxidation of sulphides by H₂O₂. Besides a mineralogical analysis, the monitoring of the pH of the extracts and the analysis of major elements (Fe, Ca, Al, Mn) can be helpful for the interpretation of the results of the sequential extraction.The combination of sequential extractions with mineralogical sample investigation provided information on the reactivity and solubility of minerals in the samples. This improved the interpretation, at least within the detection limits of the mineralogical analysis applied. Besides the improved interpretation of the results of the sequential extractions for sediments in which minerals are identified, the information concerning the reactivity of minerals is an important tool to evaluate the risk associated with contaminated sediments.     

会昌岩背锡矿田地球化学特征及隐伏矿床预测异常指标探讨

在岩背锡矿田,运用土壤地球化学异常寻找锡矿床,取得了显著效果,尤其是岩背锡矿床的发现和扩大,以及上湾隐伏锡矿床预测,为应用土壤地球化学异常找矿积累了经验。本文在阐述矿田土壤地球化学异常分布的基础上,着重对与矿床有关的土壤地球化学异常特征,以及隐伏锡矿床预测的异常指标进行了探讨。     

Contamination of water and soil by the Erdenet copper–molybdenum mine in Mongolia

As one of the largest copper–molybdenum (Cu–Mo) mines in the world, the Erdenet Mine in Mongolia has been active since 1978 and is expected to continue operations for at least another 30 years. In this study, the potential impacts of mining activities on the soil and water environments have been evaluated. Water samples showed high concentrations of sulfate, calcium, magnesium, Mo, and arsenic, and high pH values in the order of high to low as follows: tailing water > Khangal River > groundwater. Statistical analysis and the δ²H and δ¹⁸O values of water samples indicate that the tailing water directly affects the stream water and indirectly affects groundwater through recharge processes. Soil and stream sediments are highly contaminated with Cu and Mo, which are major elements of ore minerals. Based on the contamination factor (CF), the pollution load index (PLI), and the degree of contamination (C_d), soil appears to be less contaminated than stream sediments. The soil particle size is similar to that of tailing materials, but stream sediments have much coarser particles, implying that the materials have different origins. Contamination levels in stream sediments display a tendency to decrease with distance from the mine, but no such changes are found in soil. Consequently, soil contamination by metals is attributable to wind-blown dusts from the tailing materials, and stream sediment contamination is caused by discharges from uncontained subgrade ore stock materials. Considering the evident impact on the soil and water environment, and the human health risk from the Erdenet Mine, measures to mitigate its environmental impact should be taken immediately including source control, the establishment of a systematic and continuous monitoring system, and a comprehensive risk assessment.     

Study of Ni sorption onto Tio mine waste rock surfaces

Sorption phenomena are known to play significant roles in metal mobility in mine drainage waters. The present study focuses on sorption phenomena controlling Ni concentrations in contaminated neutral drainage issued from the waste rock piles of the Tio mine, a hematite–ilmenite deposit near Havre-Saint-Pierre, Québec, Canada exploited by Rio Tinto Iron and Titanium. Batch sorption tests were conducted on waste rock samples of different composition and degree of alteration, as well as on the main mineral phases purified from the waste rocks. Sorbed phases were submitted to sequential extractions, XPS and DRIFT studies for further interpretation of sorption phenomena. The results from the present study confirm that sorption phenomena play a significant role in the Tio mine waste rocks, and that the main sorbent phases are the residual ilmenite ore in waste rocks, as well as plagioclase, the main gangue mineral. Sequential extractions suggest that most sorption sites are associated with reducible fractions, and XPS results indicate that Ni is sorbed as the hydroxide Ni(OH)₂. The results from the present study provide useful information on sorption phenomena involved in the Tio mine waste rocks and enable further interpretation of Ni geochemistry in contaminated neutral drainage.     

Comparison between non-residual Al,Co, Cu,Fe, Mn,Ni, Pb and Zn released by a three-step sequential extraction procedure and a dilute hydrochloric acid leach for soil and road deposited sediment

Surprisingly little is known about the relationship between the labile phases removed by sequential extraction procedures and those liberated by single leaches that minimally impact the alumino-silicate matrix of solids. This investigation examines the relationship between the summed concentrations of Al, Co, Cu, Fe, Mn, Ni, Pb and Zn released by an optimized 3-step standardized sequential extraction procedure and those released by a single 0.5 M HCl leach. Thirty-nine representative soil and road deposited sediment samples were examined from an urban watershed, in Honolulu, Hawaii, which has been shown to have a high degree of traffic-associated pollution. Properties of samples analyzed varied widely and exhibited a range in cation exchange capacities from 7 to 59 cmol_c/kg, pH values from 3.5 to 7.9, and organic C contents from 1 to 29%. Results indicate that the dilute HCl leach was slightly more aggressive than the sequential procedure as it removed significantly more Al, Cu, Fe, Mn and Ni; though no significant differences were observed between Co, Pb and Zn concentrations liberated by the two approaches. Both approaches showed limited dissolution of the crystal lattice with ⩽9% of the total Al liberated. Regardless of approach, element mobility was the same with the order being: Pb>Mn>Zn>Co≈Cu>Ni>Fe ∼ Al. Regression analysis indicated highly significant (P<0.0001) logarithmic relationships between the two digestion procedures, with coefficients of determination (r²) ⩾92% for all elements except Fe (54%) and Ni (64%). Further support for the strong relationships between elements liberated by both digestions was gained from geochemical contrasts between anomalous and background levels and concentration enrichment ratios. This was particularly true for Pb and Zn, the most anthropogenically enhanced trace metals in the watershed. All data indicated that a dilute HCl leach was a valuable, rapid, and cost-effective analytical tool in contamination assessment.     

地质样品中Pb同位素分析的高效酸淋洗流程

针对地质样品的Pb同位素分析提出了一种简化淋洗法, 以去除样品碎样过程引起的污染.相对前人的淋洗法而言, 简化淋洗法不仅能够得到地质样品中准确的Pb同位素组成, 而且降低了全流程本底并提高了样品处理效率.利用多接收等离子体质谱分析了5个美国地质调查局(USGS) 国际标准参考物质(AGV-1、AGV-2、BHVO-2、BCR-2和G-2) 中的Pb同位素组成, 结合前人的研究, 结果表明第一、二代USGS参考物质在制样过程中均受到不同程度的污染.第一代标准在碎样过程受到的污染比碎样环境造成的普通铅污染严重, 而第二代则相反.淋洗后各种参考物质分别具有相近且均一的Pb同位素组成, 表明对岩石粉末样进行溶样前的淋洗有助于获得样品真实的Pb同位素组成.      

Removal of heavy metals from a contaminated soil using organic chelating acids

Changes in heavy metal speciation and uptake by maize in a soil before and after washing with chelating organic acids, citric acid, tartaric acid and ethylenediaminetetraacetic acid were assessed. A sandy loam was collected from the vicinity of the Benue industrial layout, Makurdi, Nigeria and spiked with a quinternary mixture of nickel, copper, zinc, cadmium and lead nitrates to achieve higher levels of contamination. Batch soil washing experiments performed on 1.0 g portions of the spiked soil using 0.05 M chelating agents at a solid:liquid ratio of 1:25 showed that washing efficiencies varied in the order: ethylenediaminetetraacetic acid> citric acid> tartaric acid with metal extraction yields typically following the sequence, copper> nickel> zinc> cadmium> lead. Sequential extractions proposed by the European Communities Bureau of Reference method used to assess the redistribution of heavy metal forms in the soil showed that apparent metal mobilities were reduced upon soil washing. Citric acid removed most of the metals hitherto associated with the exchangeable and reducible fractions; tartaric acid, the exchangeable metal pools; and ethylenediaminetetraacetic acid, the non-residual metal pools. Heavy metal assay of harvested biomass of maize grown on unwashed and washed soil samples indicated that metal transfer coefficients, decreased in the order of treatment: ethylenediaminetetraacetic acid <citric acid <tartaric acid <unwashed soil. Ethylenediaminetetraacetic acid and citric acid appeared to offer greater potentials as chelating agents to use in remediating the high permeability soil. Tartaric acid, however, is recommended in events of moderate contamination.     

长江中下游地区不同尺度铜地球化学异常的意义与大型矿床预测

以长江中下游1∶20万铜区域地球化学数据为基础,研究了铜元素地球化学异常特征,认为不同尺度的地球化学异常图具有不同的研究意义:(1)1∶20万地球化学异常可以圈定矿床异常,用于大型矿床预测。研究区内13个大型矿床中有12个落在具有三层套合结构的地球化学异常中,已知矿床储量与异常面金属量、异常面积之间的相关系数分别为0.94、0.95,显示区域地球化学异常规模与储量之间的较好相关性。(2)1∶50万地球化学异常可以圈定矿区异常,用于在成矿带中预测有利成矿区。(3)1∶100万地球化学异常可以圈定大型矿集区或成矿带,用于矿集区预测。如果把研究区内面积大于1 000km2且含有3个以上已知矿床的异常作为矿集区的话,则长江中下游存在3个大型矿集区:马鞍山—南京矿集区、九江—瑞昌—大冶矿集区和德兴—黄山—安庆—铜陵矿集区(实际上包含德兴和铜陵2个矿集区)。大型矿床多产于多层套合的地球化学异常中,大型矿集区所形成的异常具有至少3层套合结构,浓集中心与大型矿床存在对应关系,这些规律的发现为在不同成矿域预测新的大型矿集区提供了重要地球化学标志。     

Effects of historical mining activities on surface water and groundwater - an example from northwest Arizona

 The focus of this research was to determine the impact of abandoned mines on surface water and groundwater in the historical mining districts of the Cerbat Mountains, Arizona. The surface water in the mining areas was found to be contaminated by various combinations and concentrations of heavy metals. Elevated arsenic, cadmium, and iron concentrations were detected in most surface-water samples, while lead, copper, and zinc contamination differed from region to region, depending on the ore mined. The groundwater was seriously polluted by arsenic, cadmium, lead, zinc, iron, and manganese in the immediate vicinity of mines that processed ore on the site, such as the Tennessee Mine near Chloride. Chloride's groundwater, however, showed no evidence of contamination. Three possible explanations are discussed: immobilization of the heavy metals in the soil by chemical reactions and adsorption, dilution effects due to the rainy season in spring, or the existence of different groundwater systems. Received: 17 September 1996 · Accepted: 14 May 1997     

地电化学测量在河台金矿找矿预测中的应用

为了获得更多的金资源储量,对河台金矿云西矿床进行了吸附电提取法地电化学测量研究。结果显示,已知含矿糜棱岩带上方的金测试值相对围岩有较明显的高异常;未知区上方的地电化学高异常特征与含矿糜棱岩带上方的地电化学异常特征相似;未知区的地电化学高异常带方位与矿区容矿构造方位一致。以上结果说明该方法在本区进行找矿预测可行。同时指出...     

原子荧光光谱法测定土壤和水系沉积物国家标准物质中砷

用王水浸提法和硝酸-高氯酸-氢氟酸混合酸消解法处理样品,原子荧光光度光谱法测定土壤和水系沉积物国家标准物质样品中的砷。方法检出限为0.02 mg/kg。两种前处理方法砷的测定值与标准值相符,均可以满足土壤和水系沉积物样品中砷含量的测定要求。单纯测定样品中砷含量时,王水浸提法更好;如果在测定砷同时还要测定其他元素,则可以选用混合酸消解法。     

甘肃南部石鸡坝地区金地球化学特征及找矿意义

石鸡坝地区的金地球化学特征受地层、构造和沿构造发育的岩脉的控制,其水系沉积物和土壤测量的异常主元素组合为Au、Hg、As、Sb。根据不同小区的地质特征和背景,选用不同的异常下限圈定异常,尤其是Au异常,不但异常规模大,峰值高,而且具很好的浓度分带,浓集中心明显。多处异常浓集部位采用工程揭露验证,发现规模和品位较可观的金矿体,已经形成了阳山(大型)、新关(中型)、后斗湾(小型)、关牛湾(小型)等金矿床。矿体与异常的对应性相当吻合,说明水系沉积物和土壤测量方法在该区的效果和结果可靠。通过对比和分析,提出了对区内其他异常和弱小异常研究和验证的必要性,找到该类金矿的前景很大。     

酸碱污染Q3黄土的一维压缩特征试验研究

随着黄土地区工业化和城镇化的不断发展,工业废水和生活污水中酸、碱以及pH值发生改变的雨水对土壤的污染问题日渐突出,地基土体受污染后在地表建筑物荷载的作用下会发生不同程度的二次沉降次生灾害。为研究酸碱污染对Q3黄土在不同压力区间内压缩指标的变化特征,对经过不同浓度污染后的土样进行标准固结试验。试验结果表明,对比孔隙水为蒸馏水的工况,酸污染土的总变形量增大,且最大压缩变形压力段下降;碱污染土的总变形量减小,且最大压缩变形压力段上升;土样经过酸污染后压缩系数增大,中压缩性变为高压缩性,但碱污染后的压缩系数却有不同程度的降低;酸污染土的压缩系数、压缩模量、体积压缩系数和压缩指数等压缩指标在小于400 kPa的中、低压力区间更敏感,碱污染土在大于400 kPa的高压力区更敏感。在该基础上对侧限条件下的应力?应变关系进行分析,发现在不同污染情况下污染黄土的应力?应变曲线较好的符合Guanry关系。