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1.
Environmental pollution in the Kongjujeil mine creek was determined on the basis of physicochemical and mineralogical properties for various kinds of waters, soils, precipitates and sediments collected in August and December 1998. The hydrochemistry of water is characterized by an enrichment in concentrations of Ca 2+, Si, alkali ions, NO 3 - and Cl - in ground and surface water, where relatively the mine waters are significantly enriched in Ca 2++Mg 2+, Al, heavy metals and SO 4 2- concentrations. The mine waters have lower pH (3.24) and higher EC (613 µS/cm) compared with those of ground and surface water. The ranges of dD and d 18O values (SMOW) in the water are -50.2 to -61.6‰ and -7.0 to -8.6‰. Using a computer code, the saturation indices of albite, calcite and dolomite in the mine water show that it is undersaturated, and has progressively evolved toward the equilibrium state. Ground and surface water are nearly saturated. The gibbsite, kaolinite and smectite are supersaturated in the surface and groundwater. Geochemical modeling shows that mostly toxic metals exist largely in the form of metal sulfates and free metals in mine water. These metals in the surrounding fresh water could be formed of carbonate or hydroxide complex ions. Minerals within the soil and sediment near the mining area were partly variable consisting of quartz, mica, alkali feldspar, plagioclase, chlorite, vermiculite, berthierine and clay minerals. The separated heavy minerals, soil and sediment are composed of some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, malachite, goethite and various hydroxide minerals. Some potentially toxic elements (As, Cd, Cu, Pb, Sb and Zn) are found in extremely high concentrations in the surface soils in the vicinity of the mine. The enrichment index of heavy metals in sediment and surface soil of the mine drainage was very severe, while it was not so great in the cultivated soil.  相似文献   

2.
Metals released from oxidation and weathering of sulphide minerals in mine tailings are to a high degree retained at deeper levels within the tailings themselves. To be able to predict what could happen in the future with these secondarily retained metals, it is important to understand the retention mechanisms. In this study an attempt to use laser ablation high-resolution ICP-MS (LA-ICP-SMS) to quantify enrichment of trace elements on pyrite surfaces in mine tailings was performed. Pyrite grains were collected from a profile through the pyrite-rich tailings at the Kristineberg mine in northern Sweden. At each spot hit by the laser, the surface layer was analyzed in the first shot, and a second shot on the same spot gave the chemical composition of the pyrite immediately below. The crater diameter for a laser shot was known, and by estimating the crater depth and total pyrite surface, the total enrichment on pyrite grains was calculated. Results are presented for As, Cd, Co, Cu, Ni and Zn. The results clearly show that there was an enrichment of As, Cd, Cu and Zn on the pyrite surfaces below the oxidation front in the tailings, but not of Co and Ni. Arsenic was also enriched on the pyrite grains that survived in the oxidized zone. Copper has been enriched on pyrite surfaces in unoxidized tailings in the largest amount, followed by Zn and As. However, only 1.4 to 3.1% of the Cd and Zn released by sulphide oxidation in the oxidized zone have been enriched on the pyrite surfaces in the unoxidized tailings, but for As and Cu corresponding figures are about 64 and 43%, respectively. There were many uncertainties in these calculations, and the results shall not be taken too literally but allowed the conclusion that enrichment on pyrite surfaces is an important process for retention of As and Cu below the oxidation front in pyrite rich tailings. Laser ablation is not a surface analysis technique, but more of a thin layer method, and gives no information on the type of processes resulting in enrichment on the pyrite surfaces. Although only pyrite grains that appeared to be fresh and without surface coatings were used in this study, the possibility that a thin layer of Fe-hydroxides occurred must be considered. Both adsorption to the pyrite directly or to Fe-oxyhydroxides may explain the enrichment of As, Cd, Cu and Zn on the pyrite surfaces, and, in the case of Cu, also the replacement of Fe(II) by Cu(II) in pyrite.  相似文献   

3.
Mine drainage from the weathering of sulfide minerals and magnetite   总被引：1，自引：0，他引：1  
Pyrite and pyrrhotite are the principal minerals that generate acid drainage in mine wastes. Low-pH conditions derived from Fe-sulfide oxidation result in the mobilization of contaminant metals (such as Zn, Cd, Ni and Cr) and metalloids (such as As) which are of environmental concern. This paper uses data from detailed mineralogical and geochemical studies conducted at two Canadian tailings impoundments to examine the mineralogical changes that pyrite, pyrrhotite, sphalerite and magnetite undergo during and after sulfide oxidation, and the subsequent release and attenuation of associated trace elements. The stability of sphalerite in tailings impoundments generally is greater than that of pyrrhotite, but less than pyrite. Dissolved Ni and Co derived from Fe sulfides, and to a lesser extent, dissolved Zn and Cd from sphalerite, are commonly attenuated by early-formed Fe oxyhydroxides. As oxidation progresses, a recycling occurs due to continued leaching from low-pH pore waters and because the crystallinity of Fe oxyhydroxides gradually increases which decreases their sorptive capacity. Unlike many other elements, such as Cu, Pb and Cr, which form secondary minerals or remain incorporated into mature Fe oxyhydroxides, Zn and Ni become mobile. Magnetite, which is a potential source of Cr, is relatively stable except under extremely low-pH conditions. A conceptual model for the sequence of events that typically occurs in an oxidizing tailings impoundment is developed outlining the progressive oxidation of a unit of mine waste containing a mixed assemblage of pyrrhotite and pyrite.  相似文献   

4.
Soil, mine tailing, and waste dump profiles above three mesothermal gold deposits in the Bohemian Massif with different anthropogenic histories have been studied. Their mineralogical, major element, and arsenic (As) contents and the contents of secondary arsenic minerals were analyzed. The As-bearing minerals were concentrated and determined using X-ray diffraction (XRD) analysis, the Debye-Scherrer powder method, scanning electron microscopy (SEM), and energy-dispersive microanalysis (EDAX). The amorphous hydrous ferric oxides (HFO), As-bearing goethite, K-Ba- or Ca-Fe- and Fe- arsenates pharmacosiderite, arseniosiderite, and scorodite, and sulfate-arsenate pitticite were determined as products of arsenopyrite or arsenian pyrite oxidation. The As behaviour in the profiles studied differs in dependence on the surface morphology, chemical and mineralogical composition of the soil, mine wastes or tailings, oxidation conditions, pH, presence of (or distance from) primary As mineralization in the bedrock, and duration of the weathering effect. Although the primary As mineralization and the bedrock chemical composition are roughly similar, there are distinct differences in the As behaviour amongst the Mokrsko, Roudný and Kaperské Hory deposits.  相似文献   

5.
Various geological materials on the ground surface can be natural or artificial sources of pollutions. The spatial distribution of tailings is required to investigate the geological material pollutions. The objectives of this study were to determine the main factors influencing tailing zonations using a factor analysis, to determine the zonation of tailings with a cluster analysis, and to simulate zonations with three-dimensional coupled Markov chain (3D-CMC) modeling. The database was composed of 12 excavated exploratory holes in the Guryong mine tailings, for which there were analytical data covering the physical, chemical, and mineralogical aspects. The principal component analysis indicated that the tailing composition was mainly affected by three factors out of 21 variables: pH, cation exchange capacity, and mineral composition. Based on these main factors, the tailings were classified into five groups using a cluster analysis. Group I was approximately 50 cm deep from surface and had secondary gypsum (CaSO4·2H2O) and jarosite (KFe3(SO4)2(OH)6). Group II had low pH values caused by strong pyrite oxidation and the greatest amounts of the secondary minerals. In group III and IV, the quantity of the secondary minerals decreased. Group V was characterized by primary calcite (CaCO3) composition. These results were applied to the CMC modeling, and the quantitative 3D distribution of tailing was verified. For the cost-saving prediction of subsurface heterogeneity, 3D-CMC modeling was executed using the selected eight holes data among twelve holes. The unknown four holes, GS3, GS6, GS8 and GS11, are identified as 89.7, 88.6, 80.7 and 81.1 %, respectively. They are recognized as 85.0 % of the total zonation. The zonation method of tailings executed in this study can be utilized in predicting the 3D distribution of the pollution factor. This may be a useful and economical method to identify the environmentally hazardous materials in underground systems.  相似文献   

6.
Arsenic and antimony contamination is found at the Pezinok mining site in the southwest of the Slovak Republic. Investigation of this site included sampling and analysis of water, mineralogical analyses, sequential extraction, in addition to flow and geochemical modeling. The highest dissolved arsenic concentrations correspond to mine tailings (up to 90,000 μg/L) and the arsenic is present predominately as As(V). The primary source of the arsenic is the dissolution of arsenopyrite. Concentration of antimony reaches 7,500 μg/L and its primary source is the dissolution of stibnite. Pore water in mine tailings is well-buffered by the dissolution of carbonates (pH values between 6.6 and 7.0) and arsenopyrite grains are surrounded by reaction rims composed of ferric iron minerals. Based on sequential extraction results, most solid phase arsenic is in the reducible fraction (i.e. ferric oxyhydroxides), sulfidic fraction, and residual fraction. Distribution of antimony in the solid phase is similar, but contents are lower. The principal attenuation mechanism for As(V) is adsorption to ferric oxide and hydroxides, but the adsorption seems to be limited by the competition with Sb(V) produced by the oxidation of stibnite for adsorption sites. Water in mine tailings is at equilibrium with gypsum and calcite, but far from equilibrium with any arsenic and antimony minerals. The concentrations of arsenic and antimony in the surrounding aquifer are much lower, with maximum values of 215 and 426 μg/L, respectively. Arsenic and antimony are transported by ground water flow towards the Blatina Creek, but their loading from ground water to the creek is much lower compared with the input from the mine adits. In the Blatina Creek, arsenic and antimony are attenuated by dilution and by adsorption on ferric iron minerals in stream sediments with resulting respective concentrations of 93 and 45 μg/L at the site boundary south of mine tailing ponds.  相似文献   

7.
 The Sanggok mine used to be one of the largest lead-zinc mines in the Hwanggangri mining district, Republic of Korea. The present study characterizes the heavy metal contamination in the abandoned Sanggok mine creek on the basis of physico-chemical properties of various kinds of water samples (mine, surface and groundwater). Hydrochemistry of the water samples is characterized by the relatively significant enrichment of Ca2+, HCO3 –, NO3 – and Cl– in the surface and groundwaters, whereas the mine water is relatively enriched in Ca2+, Mg2+, heavy metals, and HCO3 – and SO4 2–. The more polluted mine water has a lower pH and higher Eh, conductivity and TDS values. The concentrations of some toxic elements (Al, As, Cd, Cu, Fe, Mn, Pb, Se, Sr, Pb and Zn) are tens to hundreds of times higher in the mine water than in the unpolluted surface and groundwaters. However, most immobile toxic pollutants from the mine drainage were quickly removed from the surface water by the precipitation of Al and Fe oxyhydroxides. Geochemical modeling showed that potentially toxic heavy metals might exist largely in the forms of MSO4 2– and M2+ in the mine water. These metals in the surface and groundwaters could form M2+, CO3 2– and OH– complex ions. Computer simulation indicates that the saturation indices of albite, alunite, anhydrite, chlorite, fluorite, gypsum, halloysite and strontianite in the water samples are undersaturated and have progressively evolved toward the saturation condition. However, barite, calcite, chalcedony, dolomite, gibbsite, illite and quartz were in equilibrium, and only clay minerals were supersaturated. Ground and mine waters seemed to be in equilibrium with kaolinite field, but some surface water were in equilibrium with gibbsite and seceded from the stability field of quartz. This indicates that surface water samples in reaction with carbonate rocks would first equilibrate with carbonate minerals, then gibbsite to kaolinite. Investigations on water quality and environmental improvement of the severely polluted Sanggok creek, as well as remediation methods on the possible future pollution of the groundwater by the acid mine drainage from the abandoned metal mines, are urgently required. Received: 4 February 2000 · Accepted: 9 May 2000  相似文献   

8.
《Applied Geochemistry》1998,13(6):687-705
The results of an integrated geochemical and mineralogical study conducted at the Agnico-Eagle gold-mine tailings impoundment, Joutel, Québec, are correlated with bacterial populations determined from an enumeration of 3 groups of Thiobacilli. The tailings were determined to contain approximately 5 wt.% sulphide–S, predominantly as pyrite, and up to 30 wt.% carbonate minerals, chiefly as dolomite–ankerite and siderite. The objective of the study was to evaluate the potential for the development of acidic drainage and dissolved-metal migration in carbonate-rich tailings impoundments, and to compare the results of the geochemical and microbiological characterization of the tailings. Sulphide-oxidation reactions have proceeded to a depth of 20–100 cm below the tailings surface. Pyrrhotite consistently shows more alteration than pyrite and arsenopyrite. Pyrrhotite is altered mainly through the replacement by goethite. The most abundant Thiobacilli are neutrophilic bacteria of the Thiobacillus thioparus type. The maximum most probable number values for these bacteria occur 20–40 cm below the tailings surface, a depth that coincides with the disappearance of oxide coatings. This observation, coupled with the sharp decline in gas-phase O2 concentration, suggests that rapid bacterially-mediated S–oxidation is occurring at this depth. The pore-water pH throughout the tailings varies between 6.5 and 8.5; no low-pH waters were observed in the impoundment. These neutral pH conditions are attributed to the effect of acid-consuming carbonate-mineral dissolution reactions, which are also indicated by increased concentrations of Mg and Ca and alkalinity in the shallow zone of the tailings. As a result of these acid-neutralization reactions, dissolved metal concentrations are low.  相似文献   

9.
The gold mining process at Kolar gold field (KGF) mines has generated about 32 million tons of tailings. Gold was extracted from the mined ores using cyanidation technique that involved dissolution of gold in the ore by water soluble alkali metal cyanides (example, sodium cyanide or potassium cyanide). Of the several dumps that received the mine tailings only the Kennedy’s Line dump was active prior to closure of the KGF mines in the year 2000. The Kennedy’s Line dump received sulfide bearing tailings in slurry form that comprised of spent ore and process water bearing soluble alkali metal cyanide. Depending on the pH of the tailing slurry, the free cyanides may exist as aqueous hydrogen cyanide that can escape to the atmosphere as hydrogen cyanide gas or occur as soluble cyanide (CN−) ions that can be leached by infiltrating water to the sub-surface environment. Additionally, the presence of pyrite minerals in the Kennedy’s Line dump makes them susceptible to acid drainage. This study examines the potential of gold tailings of Kennedy’s Line dump to release cyanide ions (CN−) and acid drainage to the sub-surface environment by performing physico-chemical and leaching tests with tailing samples collected from various depths of the dump, sub-surface soil samples beneath the dump and groundwater samples from vicinity of Kennedy’s Line dump. The chemical mechanisms responsible for the ambient cyanide and pH levels of the tailing dump, sub-surface soil samples and groundwater are also inferred from the laboratory results.  相似文献   

10.
Establishing a shallow water cover over tailings deposited in a designated storage facility is one option to limit oxygen diffusion and retard oxidation of sulfides which have the potential to form acid mine drainage (AMD). The Old Tailings Dam (OTD) located at the Savage River mine, western Tasmania contains 38 million tonnes of pyritic tailings deposited from 1967 to 1982, and is actively generating AMD. The OTD was constructed on a natural gradient, resulting in sub-aerial exposure of the southern area, with the northern area under a natural water cover. This physical contrast allowed for the examination of tailings mineralogy and geochemistry as a function of water cover depth across the OTD. Tailings samples (n = 144, depth: ≤ 1.5 m) were collected and subjected to a range of geochemical and mineralogical evaluations. Tailings from the southern and northern extents of the OTD showed similar AMD potential based on geochemical (NAG pH range: 2.1 to 4.2) and bulk mineralogical parameters, particularly at depth. However, sulfide alteration index (SAI) assessments highlighted the microscale contrast in oxidation. In the sub-aerial zone pyrite grains are moderately oxidized to a depth of 0.3 m (maximum SAI of 6/10), under both gravel fill and oxidized covers, with secondary minerals (e.g., ferrihydrite and goethite) developed along rims and fractures. Beneath this, mildly oxidized pyrite is seen in fresh tailings (SAI = 2.9/10 to 5.8/10). In the sub-aqueous zone, the degree of pyrite oxidation demonstrates a direct relationship with cover depth, with unoxidized, potentially reactive tailings identified from 2.5 m, directly beneath an organic-rich sediment layer (SAI = 0 to 1/10). These findings are broadly similar to other tailings storage facilities e.g., Fox Lake, Sherritt-Gordon ZnCu mine, Canada and Stekenjokk mine, Sweden where water covers up to 2 m have successfully reduced AMD. Whilst geotechnical properties of the OTD restrict the extension of the water cover, pyrite is enriched in cobalt (up to 2.6 wt%) indicating reprocessing of tailings as an alternative management option. Through adoption of an integrated mineralogical and geochemical characterization approach for tailings assessment robust management strategies after mine closure can be developed.  相似文献   

11.
Mining residues from the Sb mine of Bournac in the upper Orb River valley (Southern France), constitute an important source of As and Sb pollution. Arsenic concentrations are as high as 78 μg/L and Sb reaches 32 μg/L in the small creek draining the tailings impoundment. Although both metalloids occur mainly in oxidized form in the creek water, their behaviour differs significantly. Iron oxides are the main carrier phases for both elements in the suspended particulate matter. In oxic conditions the two elements are mainly present in water in oxidised form As(V) and Sb(V) and both field studies and laboratory experiments indicate a higher affinity of As(V) than Sb(V) for the solid phase. In the pool, which receives the water from Bournac Creek, the reductive dissolution of Fe-oxides is linked to the oxidation of small pyrite grains transported from the tailings dump. In oxic conditions Sb is released to solution more efficiently than As. Conversely, in anoxic conditions, mobilisation of As is greater than that of Sb. This is attributed to the reduction of As, which favours its mobility. Whatever the conditions, the activity of bacteria naturally present in the sediments enhances the remobilization of Sb in oxidizing conditions and that of As in reducing conditions.  相似文献   

12.
The wall rocks of Sidi Driss mineralization contain continental molassic deposits: lacustrine limestones, ferruginous fragments, Ed Diss unit and Numidian unit fragments, rhyodacitic fragments, pyroclasts, and gneissic fragments. The ore is composed of pyrite, marcasite, sphalerite, galena, barite, celestite, siderite, calcite, and iron oxide-hydroxides. The abandoned wastes in Sidi Driss-Tamra district contain marcasite, galena, goethite, jarosite, anglesite, anhydrite, bassanite, and gypsum. It is very important to assess the hazards and risks that this material type poses to public health and the environment. However, evaluation of a part of toxic elements always poses problems since the associated matrix, the close relationships between some minerals, the grain sizes and their forms (oolites, compact collomorphes aggregate), the oxidation degree of metals, the chemical composition, and trace elements make it difficult to extract mobile metals from complex Sidi Driss tailings and minerals found in these acidic wastes. Nevertheless, there is no universal method that can systematically evaluate metal bioavailability. And the use of proposed sequential extraction procedures for sediments with simple mineralogical composition did not yield any reproducible results for this type of acid mine drainage sediments. Consequently, the methods of controlling and mitigating the risks of hazardous materials should be considered. Many extraction procedures have been applied to better evaluate the mobility of hazardous materials (metals), the characterization of their degree of toxicity, and their chemical behavior in these complex mine tailings. Reproducible results were obtained with lab-scale washing of sediments using distilled water, CaCl2 and Na2-EDTA solutions, and BCR sequential extraction. The results showed that the BCR extraction approach was the most efficient procedure for these types of wastes. The extraction with distilled water is recommended for identification of the total quantity of mobile Cr and Fe.  相似文献   

13.
Different plant communities have established spontaneously on Sanmen Pb/Zn mine tailing. The site was inspected and four different plant communities were identified according to their species composition. To understand the effects of different communities on mine tailing physico-chemical properties, a community survey was carried out in Sanmen Pb/Zn mine tailing, and the physico-chemical properties and heavy metal (Cu, Pb, Cd and Zn) distribution of mine tailings were determined. Results showed that there were four types of communities (I, II, III and IV) in Sanmen Pb/Zn mine tailing. From community I to IV, the number of plant species and community characteristics (aboveground biomass, underground biomass, coverage and height) consistently increased. Moreover, the nutrient pool and physico-chemical properties of mine tailing consistently reestablished from community I to IV, while the total heavy metal content consistently decreased. The contents of residual fractions, Fe–Mn oxide fractions for Pb, Zn, Cu and Cd and exchangeable fractions for Pb and Zn also consistently decreased. However, the contents of organically bound fraction had no obvious change from community I to IV. Moreover, the contents of Cu organically bound fraction reversely increased. Results demonstrate that communities I, II, III and IV should be a progressive community succession. Moreover, along with the progressive community succession, phytostabilization and phytoextraction of mine tailings are more and more effective.  相似文献   

14.
Historical gold mining operations in Nova Scotia, Canada, resulted in numerous deposits of publicly accessible, arsenic (As)-rich mine waste that has weathered in situ for 75–150 years, resulting in a wide range of As-bearing secondary minerals. The geochemical heterogeneity of this mine waste creates a challenge for identifying a single remediation approach that will limit As mobility. A 30-cm-thick, low-organic content soil cover was evaluated in a laboratory leaching experiment where, to simulate natural conditions, the equivalent of 2 years of synthetic rainwater was leached through each column and two dry seasons were incorporated into the leaching protocol. Each column was a stratigraphic representation of the four major tailings types found at the historical Montague and Goldenville gold mine districts: hardpan tailings, oxic tailings, wetland tailings, and high Ca tailings. Hardpan tailings released acidic, As-rich waters (max 12 mg/L) under the soil cover but this acidity was buffered by surrounding oxic tailings. Leachate from the oxic tailings was circumneutral, with average As concentrations between 4.4 and 9.7 mg/L throughout the experiment. The presence of carbonates in the high Ca tailings resulted in near-neutral to weakly alkaline leachate pH values and average As concentrations between 2.1 and 6.1 mg/L. Oxidation of sulfides in the wetland tailings led to acidic leachate over time and a decrease in As concentrations to values that were generally less than 1 mg/L. This study shows that the use of a low-organic content soil cover does not create reducing conditions that would destabilize oxidized, As-bearing secondary phases in these tailings. However, oxygen penetration through the cover during dry seasons would continue to release As to tailings pore waters via sulfide oxidation reactions.  相似文献   

15.
Mineral extraction and processing, especially metal mining, produces crushed and milled waste; such material, exposed to weathering, poses the potential threat of environmental contamination. In this study, mill tailings from inactive Pb-Zn mines in New Mexico, southwest USA, have been examined for their potential environmental impacts by means of detailed mineralogical and geochemical characterization. The principal ore minerals remaining in the tailings material are sphalerite, chalcopyrite, and very minor galena, smithsonite, and cerrusite, accompanied by the gangue minerals pyrite, pyrrhotite, magnetite, hematite, garnet, pyroxene, quartz, and calcite. White precipitate occurring on tailings surfaces is composed of gypsum and hydrated magnesium sulfates. Pyrite is mostly unaltered or shows only micron-scale rims of oxidation (goethite/hematite) in some surface samples. This iron oxide rim on pyrite is the only indication of weathering-derived minerals found by microscopy. There are variations in element concentrations with depth that reflect primary variations through time as the tailings ponds were filled. Cadmium and Zn concentrations increase with depth and Ag and Pb are low for the uppermost core samples, while Cu, Ni, and Co concentrations are generally high for the uppermost core samples. These elemental distributions indicate that little or no leaching has taken place since emplacement of the tailings because no accumulation or enrichment of these metals is observed in Hanover tailings, even in reducing portions of tailings piles. Element concentrations of surface samples surrounding the tailings reflect underlying mineralized zones rather than tailings-derived soil contamination. We observed no successive decreasing metal concentrations in prevalent wind directions away from the tailings. Stream sediment samples from Hanover Creek have somewhat elevated Zn, Cd, and Pb concentrations in areas that receive sediments from erosion of the tailings. However, input from tributaries downstream of the ponds appears to be principal source of heavy metals in Hanover Creek. The results of this study indicate that there is low risk for groundwater heavy-metal contamination from Hanover tailings. Tailings material do not show significant geochemical oxidation/alteration or metal leaching with depth. Our studies indicate that neutralizing minerals present in the tailings are sufficient to keep the tailings material chemically stable. Geochemically, however, tailings materials are being eroded and may pose a threat to Hanover Creek via siltation.  相似文献   

16.
Carbonate concretions, lenses and bands in the Pleistocene, Palaeogene and Upper Triassic coalfields of Japan consist of various carbonate minerals with varied chemical compositions. Authigenic carbonates in freshwater sediments are siderite > calcite > ankerite > dolomite >> ferroan magnesite; in brackish water to marine sediments in the coal measures, calcite > dolomite > ankerite > siderite >> ferroan magnesite; and in the overlying marine deposits, calcite > dolomite >> siderite. Most carbonates were formed progressively during burial within a range of depths between the sediment-water interface and approximately 3 km. The mineral species and the chemical composition of the carbonates are controlled primarily by the initial sedimentary facies of the host sediments and secondarily by the diagenetic evolution of pore water during burial. Based on the regular sequence and burial depth of precipitation of authigenic carbonates in a specific sedimentary facies, three diagenetic stages of carbonates are proposed. Carbonates formed during Stage I (< 500 m) strongly reflect the initial sedimentary facies, e.g. low Ca-Mg siderite in freshwater sediments which are initially rich in iron derived from lateritic soil on the nearby landmass, and Mg calcite and dolomite in brackish-marine sediments whose pore waters abound in Ca2+ and Mg2+ originating in seawater and calcareous shells. Carbonates formed during Stage II (500–2000 m) include high Ca-Mg siderite, ankerite, Fe dolomite and Fe–Mg calcite in freshwater sediments. The assemblage of Stage II carbonates in brackish-marine sediments in the coal measures is similar to that in freshwater sediments. This suggests similar diagenetic environments owing to an effective migration and mixing of pore water due to the compaction of host sediments. Carbonates formed during Stage III (> 2000 m) are Fe calcite and extremely high Ca-Mg siderite; the latter is exclusively in marine mudstones. The supply of Ca is partly from the alteration of silicates in the sediments at elevated burial temperatures. After uplift, calcite with low Mg content precipitates from percolating groundwater and fills extensional cracks.  相似文献   

17.
This study presents the mineralogical and geochemical characteristics of tailing dumps at the Krasnorechenskaya concentration mill (Primorskii krai, Russia). Primary ore minerals and newly forming mineral assemblages were also investigated. According to the obtained data, the possible reserves of the major elements accumulated in these tailings were estimated. It was shown that the tailing dumps at the Krasnorechenskaya concentration mill are potentially promising for secondary recovery. The tailing sediment has natural geochemical stratification and the specific correlations of elements are typical for each selected layer.  相似文献   

18.
The origin of high dissolved manganese concentrations in slightly acidic mine runoff from a surface mine operated by the Cumberland Coal Company in eastern Tennessee was investigated. Mineralogical and chemical analyses were performed on 31 samples of sandstone, shale, coal, and mudstone from the mine to identify the sources and stratigraphic distribution of high extractable manganese contents in the spoil materials. The samples were analyzed for their bulk mineral content by X-ray diffraction, net acid-base potential, and reaction to 2 or 4 chemical extraction procedures. A limited number of samples were analyzed for petrographic characteristics, clay mineral composition by X-ray diffraction, and mineral compositions by electron microprobe. Analysis of the data and consideration of the geochemical conditions at the mine were used to identify probable sources for the high extractable manganese contents.The results indicate 2 prominent, independent sources of extractable manganese. The first source is exchangeable manganese on clay minerals (mainly illite + muscovite and chlorite) and is concentrated in shale and mudstone rock types. The second and more significant source is manganese in siderite concretions and cement, mainly in shale and mudstone. Comparison to other coal-bearing strata indicates that manganese-rich siderite is common in fresh- to brackish-water subaqueous sediments that overlie coal. This is especially the case for coals formed in wet, tropical environments.Ratios of manganese to calcium and magnesium in mine runoff suggest that manganese from siderite is the major cause of the high dissolved manganese contents. A conceptual model is developed to explain the high manganese contents of the mine runoff. Oxidation of pyrite creates mildly acidic waters that are subsequently partially neutralized by reaction with impure siderite. Solubilized manganese remains dissolved in the slightly acidic runoff water, whereas dissolved iron precipitates as ferric hydroxide or goethite. Consideration of data from other coal mining regions suggests that similar reactions involving impure siderite may be responsible for high manganese concentrations in acidic to slightly acidic mine runoff. Geochemical reaction path modeling of pyrite and impure siderite with rainwater illustrate how resulting water compositions may vary depending on pyrite to siderite ratios in spoil materials. Spoil water compositions from the Cumberland mine are largely consistent with reaction of pyrite and impure siderite in proportions observed in the sediments; however, deviations may be explained by minor mixing with waters that reacted only with impure siderite or clay mineral exchange reactions.  相似文献   

19.
The potentially hazardous contents of mine tailings can pose a serious threat to the environment. Tailings dispersed around the abandoned Monica mine (Bustarviejo) in the Autonomous Region of Madrid (Central Spain) were studied to determine the concentration of several potential toxic elements and their geochemical impact in the surrounding soils. A total of 17 surface soil samples were collected from both mixed sulfide mine tailings sites and unmined soils, within a radius of 1900 m from the mine entrance. The processing of minerals (basically arsenopyrite, matildite and sphalerite) produced tailings with a pH as low as 2.9. Elements such as As, Cu, Zn, Cd, Pb, W, Ag, Fe were found in very high concentrations, contaminating the soil to varying degrees (these elements were sometimes 10- to 20-times higher in the tailings than in the unmined soils). Given its short distance and accessibility from such a large city as Madrid, it is of undeniable environmental and educational interest. Among other factors, there is a need for improvements to tailings management strategies.  相似文献   

20.
运用偏光显微镜、低温灰化+X射线衍射仪、带能谱的扫描电镜对内蒙古大青山煤田阿刀亥矿晚古生代CP2煤层中矿物的赋存状态及其成因进行了研究.研究表明阿刀亥矿CP2煤层中矿物包括硬水铝石、勃姆石、磷钡铝石、高岭石、铵伊利石、方解石、白云石、菱铁矿、锐钛矿、氟磷灰石、石英和黄铁矿.硬水铝石、勃姆石、磷钡铝石、高岭石和铵伊利石一般充填在丝质体、半丝质体、结构镜质体胞腔中或者分布在基质镜质体中.方解石和白云石主要充填在裂隙中.硬水铝石、勃姆石和磷钡铝石是由来源于本溪组铝土矿风化壳的物质在泥炭聚集时沉积形成的.铵伊利石是由于花岗岩侵入体的影响形成的.方解石和白云石可能来源于岩浆热液.  相似文献   

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