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排序方式: 共有542条查询结果,搜索用时 468 毫秒
221.
Dispersed alkaline substrates (DAS) have been successfully used in passive treatment of highly contaminated acid mine drainage (AMD) to limit coating and clogging issues. However, further optimization of DAS systems is still needed, especially for their long-term efficiency during the treatment of ferriferous AMD. In the present study, three types of DAS comprised of natural alkaline materials (wood ash, calcite, dolomite), in different proportions (20%v/v, 50%v/v, 80%v/v), and a substrate with high surface area (wood chips) were tested in 9 batch reactors. The testing was carried out, in duplicate, for a period of 91 days, to evaluate the comparative performance of the mixtures for iron pre-treatment in ferriferous AMD (2500 mg/L Fe, at pH 4). Results showed increasing of pH (between 4.15 and 7.12), regardless of the proportion of alkaline materials in the DAS mixtures. Among the tested mixtures, wood ash type DAS were more effective for Fe removal (99.9%) than calcite or dolomite type DAS (up to 66%). All tested DAS had limited efficiency for sulfate removal and an additional treatment unit, such as a sulfate-reducing biochemical reactor, is needed. Moreover, due to the similar performances of the calcite and dolomite DAS, they could be potentially substituted and rather be used in a polishing treatment unit. Based on these findings, the most promising mixture was the 50% wood ash type DAS (WA50-DAS). 相似文献
222.
Carlos Alberto Spier Sonia Maria Barros de Oliveira Carlos Alberto Rosière José Domingos Ardisson 《Mineralium Deposita》2008,43(2):229-254
Several major iron deposits occur in the Quadrilátero Ferrífero (QF), southeastern region of Brazil, where metamorphosed and heterogeneously deformed banded iron formation (BIF) of the Cauê Formation, regionally called itabirite, was transformed into high- (Fe >64%) and low-grade (30%?2O3, with a higher amount of detrimental impurities, especially MnO, in the soft ore. Both hard and soft ores are depleted in trace elements. The high-grade ores at the Águas Claras Mine have at least a dual origin, involving hypogene and supergene processes. The occurrence of the hard, massive high-grade ore within “fresh” dolomitic itabirite is evidence of its hypogene origin. Despite the contention about the origin of the dolomitic itabirite (if this rock is a carbonate-rich facies of the Cauê Formation or a hematite–carbonate precursor of the soft high-grade ore), mineralogical and geochemical features of the soft high-grade ore indicate that it was formed by leaching of dolomite from the dolomitic itabirite by meteoric water. The comparison of the Águas Claras, Capão Xavier and Tamanduá orebodies shows that the original composition of the itabiritic protore plays a major role in the genesis of high- and low-grade soft ores in the QF. Under the same weathering and structural conditions, the dolomitic itabirite is the more favorable to form high-grade deposits than siliceous itabirite. Field relations at the Águas Claras and Capão Xavier deposits suggest that it is not possible to form huge soft high-grade supergene deposits from siliceous itabirite, unless another control, such as impermeable barriers, had played an important role. The occurrence in the Tamanduá Mine of a large, soft, high-grade orebody formed from siliceous itabirite and closely associated with hypogene hard ore suggests that large, soft, high-grade orebodies of the Quadrilátero Ferrífero, which occur within siliceous itabirite, have a hypogene contribution in their formation. 相似文献
223.
The Chemical Speciation of Fe(III) in Freshwaters 总被引:1,自引:0,他引:1
Dialysis and chemical speciation modelling have been used to calculate activities of Fe3+ for a range of UK surface waters of varying chemistry (pH 4.3–8.0; dissolved organic carbon 1.7–40.3 mg l−1) at 283 K. The resulting activities were regressed against pH to give the empirical model: . Predicted Fe3+ activities are consistent with a solid–solution equilibrium with hydrous ferric oxide, consistent with some previous studies
on Fe(III) solubility in the laboratory. However, as has also sometimes been observed in the laboratory, the slope of the
solubility equation is lower than the theoretical value of 3. The empirical model was used to predict concentrations of Fe
in dialysates and ultrafiltrates of globally distributed surface and soil/groundwaters. The predictions were improved greatly
by the incorporation of a temperature correction for , consistent with the temperature dependence of previously reported hydrous ferric oxide solubility. The empirical model,
incorporating temperature effects, may be used to make generic predictions of the ratio of free and complexed Fe(III) to dissolved
organic matter in freshwaters. Comparison of such ratios with observed Fe:dissolved organic matter ratios allows an assessment
to be made of the amounts of Fe present as Fe(II) or colloidal Fe(III), where no separate measurements have been made.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
224.
Takeru Moriyama Mruganka K. Panigrahi Dinesh Pandit Yasushi Watanabe 《Resource Geology》2008,58(4):402-413
The major, trace and rare earth element (REE) composition of Late Archean manganese, ferromanganese and iron ores from the Iron Ore Group (IOG) in Orissa, east India, was examined. Manganese deposits, occurring above the iron formations of the IOG, display massive, rhythmically laminated or botryoidal textures. The ores are composed primarily of iron and manganese, and are low in other major and trace elements such as SiO2, Al2O3, P2O5 and Zr. The total REE concentration is as high as 975 ppm in manganese ores, whereas concentrations as high as 345 ppm and 211 ppm are found in ferromanganese and iron ores, respectively. Heavy REE (HREE) enrichments, negative Ce anomalies and positive Eu anomalies were observed in post‐Archean average shale (PAAS)‐normalized REE patterns of the IOG manganese and ferromanganese ores. The stratiform or stratabound shapes of ore bodies within the shale horizon, and REE geochemistry, suggest that the manganese and ferromanganese ores of the IOG were formed by iron and/or manganese precipitation from a submarine, hydrothermal solution under oxic conditions that occurred as a result of mixing with oxic seawater. While HREE concentrations in the Late Archean manganese and ferromanganese ores in the IOG are slightly less than those of the Phanerozoic ferromanganese ores in Japan, HREE resources in the IOG manganese deposits appear to be two orders of magnitude higher because of the large size of the deposits. Although a reliable, economic concentration technique for HREE from manganese and ferromanganese ores has not yet been developed, those ores could be an important future source of HREE. 相似文献
225.
邯邢式铁矿是河北省重要的铁矿成因类型,已经探明资源储量达到8.7亿吨。以往在该地区经过了由高磁异常验证-复杂异常查证-低缓异常查证的过程,实践证明磁法找矿为邯邢式铁矿找矿的基本方法。随着找矿难度的逐步加大,对地质控矿条件的分析越来越重要。目前,该地区浅部铁矿资源基本探明,正在该地区开展邯邢式铁矿的深部找矿工作。回顾原来的找矿方法,对今后开展工作是十分有益的。本文以邯邢式铁矿的岩矿石物性(磁化率、密度、电阻率等)特点为主要依据,在前人实验的基础上,提出重磁电综合物探方法是今后邯邢式铁矿的找矿方法的发展方向,加强物探数据的综合处理和地质成矿条件相结合是该地区进行深部找矿的前提和基础。 相似文献
226.
A. L. Pickard 《Australian Journal of Earth Sciences》2013,60(3):491-507
Tuffaceous mudrocks are common in the banded iron‐formations (BIF) of the Brockman Iron Formation. These tuffaceous mudrocks are either stilpnomelane‐rich or siliceous. Their compositions reflect bimodal volcanic activity in the vicinity of the Hamersley BIF depositional site. They also contain complex zircon populations that record resedimentation, syndepositional volcanism and post‐depositional isotopic disturbance. The best estimates of depositional age are obtained from siliceous tuffaceous mudrocks in the Joffre Member that contain 2459 ± 3 Ma and 2454 ± 3 Ma zircon populations most likely derived from felsic volcanism coeval with BIF deposition. These dates constrain the sedimentation rates for the ~370 m‐thick Joffre Member BIF to >15 m per million years. Siliceous tuffaceous mudrocks are not present in the underlying ~120 m‐thick Dales Gorge Member and it is uncertain whether previously reported ages of ca 2479–2470 Ma for this unit reflect detrital/xenocrystic or syndepositional zircon populations in resedimented stilpnomelane‐rich tuffaceous mudrocks. The increased abundance of tuffaceous mudrocks in the Joffre Member suggests that a pulse of enhanced igneous and hydrothermal activity accompanied deposition of the bulk of the Brockman Iron Formation BIF after ca 2460 Ma. This preceded and culminated in the emplacement of the 2449 ± 3 Ma large igneous province represented by BIF and igneous rocks of the Weeli Wolli Formation and Woongarra Rhyolite. 相似文献
227.
坦桑尼亚某金矿的磁力、激电异常特征 总被引:3,自引:0,他引:3
坦桑尼亚某金矿是与条带状含铁建造(BIF)有关的隐伏金矿床。为了查明该金矿脉的分布情况,开展了地面高精度磁力勘查。△T异常特征以负异常为主,负异常峰值大于正异常,正异常为伴生异常,总体上反映了BIF在平面上的延伸方向和构造方向特征;激电测深断面异常以视电阻率等值线“下凹”、视极化率等值线“上凸”为表现形式,二者分别反映了断面内的构造位置和BIF形态特征。本区磁力和激电异常对BIF体的隐伏特征反映的均很明显,依据二者的测量成果,进行钻孔定位,指导钻探施工,钻遇了目的层,收到了很好的效果。 相似文献
228.
229.
Silicate-bearing iron meteorites differ from other iron meteorites in containing variable amounts of silicates, ranging from minor to stony-iron proportions (∼50%). These irons provide important constraints on the evolution of planetesimals and asteroids, especially with regard to the nature of metal–silicate separation and mixing. I present a review and synthesis of available data, including a compilation and interpretation of host metal trace-element compositions, oxygen-isotope compositions, textures, mineralogy, phase chemistries, and bulk compositions of silicate portions, ages of silicate and metal portions, and thermal histories. Case studies for the petrogeneses of igneous silicate lithologies from different groups are provided. Silicate-bearing irons were formed on multiple parent bodies under different conditions. The IAB/IIICD irons have silicates that are mainly chondritic in composition, but include some igneous lithologies, and were derived from a volatile-rich asteroid that underwent small amounts of silicate partial melting but larger amounts of metallic melting. A large proportion of IIE irons contain fractionated alkali-silica-rich inclusions formed as partial melts of chondrite, although other IIE irons have silicates of chondritic composition. The IIEs were derived from an H-chondrite-like asteroid that experienced more significant melting than the IAB asteroid. The two stony-iron IVAs were derived from an extensively melted and apparently chemically processed L or LL-like asteroid that also produced a metallic core. Ungrouped silicate-bearing irons were derived from seven additional asteroids. Hf–W age data imply that metal–silicate separation occurred within 0–10 Ma of CAI formation for these irons, suggesting internal heating by 26Al. Chronometers were partly re-set at later times, mainly earlier for the IABs and later for the IIEs, including one late (3.60 ± 0.15 Ga) strong impact that affected the “young silicate” IIEs Watson (unfractionated silicate, and probable impact melt), Netschaëvo (unfractionated, and metamorphosed), and Kodaikanal (fractionated). Kodaikanal probably did not undergo differentiation in this late impact, but the similar ages of the “young silicate” IIEs imply that relatively undifferentiated and differentiated materials co-existed on the same asteroid. The thermal histories and petrogeneses of fractionated IIE irons and IVA stony irons are best accommodated by a model of disruption and reassembly of partly molten asteroids. 相似文献
230.
Fernando Pérez-Lambán José Luis Peña-Monné Javier Fanlo-Loras Jesús V. Picazo-Millán David Badia-Villas Virginia Rubio-Fernández Rosario García-Giménez María M. Sampietro-Vattuone 《Quaternary Research》2014
Slope deposits in semiarid regions are known to be very sensitive environments, especially those that occurred during the minor fluctuations of the late Holocene. In this paper we analyse Holocene colluvium genesis, composition, and paleoenvironmental meaning through the study of slope deposits in NE Spain. Two cumulative slope stages are described during this period. In the study area, both slope accumulations are superimposed and this has enabled an excellent preservation of the aggregative sequence and the paleosols corresponding to stabilisation stages. 14C and TL dating, as well as archaeological remains, provide considerable chronological precision for this sequence. The origin of the accumulation of the lower unit is placed around 4295–4083 cal yr BP/2346–2134 cal yr BC (late Chalcolithic) and it developed until the Iron Age in a cooler and wetter climate (Cold Iron Age). Under favourable conditions, a soil A-horizon was formed on top of this unit. A new slope accumulation was formed during the Little Ice Age. Within the slope two morphogenetic periods ending with A-horizons are distinguished and related with two main cold–wet climatic events. The study of these slopes provides a great amount of data for the paleoenvironmental and geoarchaeological reconstruction of the late Holocene in NE Spain. 相似文献