| 1. |
- Axelsson, Mikael D., et al.
(author)
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Determination of major and trace elements in sphalerite using laser ablation double focusing sector field ICP-MS
- 2001
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In: Journal of Geochemical Exploration. - 0375-6742 .- 1879-1689. ; 72:2, s. 81-89
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Journal article (peer-reviewed)abstract
- The analytical performance of laser ablation (LA) for the determination of Co, Fe, Cd, Ag, Mn, Cu and S in sphalerite was evaluated using double focusing sector field inductively coupled plasma mass spectrometry (ICP-SFMS). Samples were collected from Zinkgruvan, situated in the south central Sweden. The use of Zn for internal standardisation, together with correction for FeS impurities in sphalerite, allows straightforward quantification without using external methods for the determination of the actual Zn content. LA-ICP-SFMS results were compared with data obtained by conventional pneumatic nebulisation introduction of sample solutions following acid digestion. Good agreement between the two methods was obtained for homogeneously distributed elements. For the majority of the elements under consideration, LA-ICP-SFMS precision was better than 10% RSD.
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| 2. |
- Banwart, S. A., et al.
(author)
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Hydrochemical modelling for preliminary assessment of minewater pollution
- 2001
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In: Journal of Geochemical Exploration. - 0375-6742 .- 1879-1689. ; 74:03-jan, s. 73-97
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Journal article (peer-reviewed)abstract
- A conceptual model for preliminary assessment of minewater pollution within the risk-based corrective action (RBCA) framework for environmental management is developed. The model aims to assist classification of a site regarding the potential threat to the environment and help assess whether the assumptions used in this classification are appropriate. The model estimates contamination source strength, longevity and possible future changes in discharge quality and can be applied with sparse data sets. The model relates solute export in the discharge to source minerals which includes sulphide phases that produce acidity and metals contamination and carbonate and aluminosilicate phases which provide natural attenuation to neutralise acidity and immobilise metals. We present and apply limited data from three sites representing a mine rock waste deposit located above the water table, a flooded abandoned coal mine with deep workings and a mine tailings deposit. Results from the rock waste deposit indicate that calcite no longer provides significant attenuation of the present acidity load and that acid generation and associated loads of Cu2+ may persist for a period of up to two centuries. The abandoned coal mine has a discharge that is presently alkaline, with calcite depletion expected to occur before pyrite is consumed, possibly yielding a future drop in pH. The lifetime for these minerals is similar at this site, and on the order of several centuries, thus rendering the estimate of future water quality evolution very uncertain. The mill tailings deposit is expected to produce acidic discharge on a time scale of one century. However, conclusive quantification of calcite weathering was not possible, leaving open the possibility that the weathering of Mg-silicate minerals provides important attenuation of the present acidity load.
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| 3. |
- Gleisner, M., et al.
(author)
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Sulfide mineral oxidation in freshly processed tailings : batch experiments
- 2002
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In: Journal of Geochemical Exploration. - 0375-6742 .- 1879-1689. ; 76:3, s. 139-153
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Journal article (peer-reviewed)abstract
- This work focuses on sulfide mineral oxidation rates under oxic conditions in freshly processed pyrite-rich tailings from the ore concentrator in Boliden, northern Sweden. Freshly processed tailings are chemically treated in the plant to kill bacteria and to obtain increased metal yields, resulting in a high pH level of 10-12 in the process water. Different oxidation experiments (abiotic oxidation in untreated tailings, acid abiotic oxidation and acid microbial oxidation), containing the Boliden tailings, were performed at room temperature with dissolved oxygen (0.21 atm O-2) for 3 months. The different pyrite oxidation rates given from the study were 2.4 x 10(-10) mol m(-2) s(-1) for the microbial, 5.9 x 10(-11) mol m(-2) s(-1) for the acidic abiotic and 3.6 x 10(-11) mol m(-2) s(-1) for the untreated experiments. Because of the potential precipitation of gypsum in the batch solutions, these oxidation rates are considered minimum values. The release rates for copper and zinc from chalcopyrite and sphalerite in the acid experiments were also investigated. These rates were normalized to the metal concentration in the tailings, and then compared to the release rate for iron from pyrite. These normalized results indicated that metal release decreased in the order Cu>Zn>Fe, demonstrating that pyrite is more resistant to oxidation than sphalerite and chalcopyrite. Pyrite was also more resistant to acidic dissolution than to microbial dissolution, while a significant fraction of sphalerite and chalcopyrite dissolved in the acid abiotic solutions.
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| 4. |
- Holmstrom, H., et al.
(author)
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Layers rich in Fe- and Mn-oxyhydroxides formed at the tailings-pond water interface, a possible trap for trace metals in flooded mine tailings
- 2001
-
In: Journal of Geochemical Exploration. - 0375-6742 .- 1879-1689. ; 74:1-3, s. 189-203
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Journal article (peer-reviewed)abstract
- Geochemical field studies of the flooded sulphide-rich mine tailings at Stekenjokk in northern Sweden have been performed. Minor diffusion of elements from the tailings to the pond water is occurring. The diffusion rate is higher where tailings that were oxidised before the flooding have been deposited. Layers rich in Fe-and Mn-oxyhydroxides have been developed close to the tailings surface, and a layer of natural sediments rich in organic material have developed on the tailings surface since the flooding. The oxyhydroxides adsorb and/or co-precipitate metals and function as a trap for released metals at the tailings-pond water interface, thereby decreasing the diffusion rate from the tailings pore water to the pond water at the sediment-water interface. This study shows that it is possible for a deposit of flooded tailings to reach a state when it almost functions as a natural lake in northerly areas, with Fe-and Mn-oxyhydroxide layers controlling the diffusion of metals into the overlying pond water, within a relatively short time after remediation. © 2001 Elsevier Science B.V. All rights reserved.
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| 5. |
- Land, Magnus, et al.
(author)
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Trace metal occurrence in a mineralised and a non-mineralised Spodosol in northern Sweden
- 2002
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In: Journal of Geochemical Exploration. - 0375-6742 .- 1879-1689. ; 75:1-3, s. 71-91
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Journal article (peer-reviewed)abstract
- In order to determine the metal-bearing phases with special emphasis on Cu, a sequential extraction has been carried out on seven soil samples from a sulphide-bearing spodosol profile in Liikavaara Ostra, close to the Aitik Copper Mine in northern Sweden. A reference spodosol profile with very low abundances of sulphides located far from anthropogenic emissions was also studied. Five fractions were selected for the extraction: (I) CH (sub 3) COONa-extractable (exchangeable/adsorbed/carbonate); (II) Na (sub 4) P (sub 2) O (sub 7) -extractable (labile organics); (III) 0.25 M NH (sub 2) OH.HCl-extractable (amorphous Fe oxyhydroxides/Mn oxides); (IV) 1 M NH (sub 2) OH.HCl-extractable (crystalline Fe oxides); and (V) KClO (sub 3) /HCl-extractable (organics and sulphides). The distribution of trace elements (Co, Cr, Cu, Ni, Pb and Zn) in the profile in Liikavaara Ostra is different from that in the reference profile. Possible explanations for these differences are (i) the presence of sulphides in the soil, (ii) atmospheric deposition of dust derived from mining activities at the Aitik Copper Mine, and (iii) mineralogical heterogeneities inherited from the deposition of the till. There is no straightforward correlation between the amount of the extracted phases and the metal extractability in the soils. This fact indicates that other factors are important for the retention of trace metals as well. The data presented in this study suggest that Co, Cr and Ni, to a fairly large extent, are associated with the organic matter in the B-horizon in both profiles, while in the C-horizon in Liikavaara Ostra, sulphides are probably the more important carriers of these elements. For Co and Ni, Fe oxyhydroxides seem to be important. Most of the Cr occurred in the residual remaining after the leaching procedure. Copper and Zn seem to be associated with the organic matter to some extent in the B-horizon. The concentration of Cu in the C-horizon in Liikavaara Ostra is high (2310 ppm), but only a very small fraction is likely to be hosted by sulphides. It is concluded that the major part of Cu in the C-horizon and a prominent fraction in the B-horizon in Liikavaara Ostra are associated with some secondary phase that is extractable during extractions III and IV. Possible candidates for this phase are goethite and inclusions of native Cu in weathered biotite
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| 6. |
- Ljungberg, Johan, et al.
(author)
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The geochemical dynamics of oxidizing mine tailings at Laver, northern Sweden
- 2001
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In: Journal of Geochemical Exploration. - 0375-6742 .- 1879-1689. ; 74:1-3, s. 57-72
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Journal article (peer-reviewed)abstract
- former Cu mine Laver in northern Sweden was selected for a study of the geochemical processes in mine tailings. The Laver mine was in operation between 1936 and 1946, producing approximately 1.2 Mt of tailings. This study of the tailings at Laver includes time series of groundwater and surface water chemistry, chemical and mineralogical studies of the tailings sand and geophysical investigations. The results allow a good understanding of the dynamic geochemical processes taking place within the tailings. Oxidation of sulphide minerals in the tailings has led to the development of a distinct chemical zonation. Metals released from oxidation and weathering of sulphide minerals are retained within the tailings impoundment. This retention mechanism is today very efficient and only 5-10% of the released masses of metals reaches the surface water system. Zn, Cd, Co and Ni are probably secondarily bound to the tailings with adsorption in a large mass of non-weathered tailings. Cu, on the other hand, is enriched in a distinct zone just below the front of oxidation. This distinct Cu-enrichment suggests precipitation of a secondary mineral phase, probably covellite. The downward movement of the front of oxidation advances at a rate of 2.8 cm/a, and displaces the secondary zone with Cu-enrichment at the same rate. When the oxidation front reaches the groundwater table, the oxidation of sulphide minerals will almost completely stop. The Cu-enrichment will, in this case, probably partly go into solution and be transported away by the groundwater movement. The seepage of acid water from the oxidation front will consume pH-buffering capacity of the tailings and the groundwater will eventually become more acidic. Such a low pH-environment in the tailings will force the adsorbed Zn, Cd, Co and Ni to go into solution and be transported away. A front of water with low pH and high concentrations of metals has been detected and is moving towards the outlets of the tailing impoundment. Due to the low hydraulic gradient and conductivity, the front of acid metal-rich water will be delayed in time by 10-30 years before it reaches the recipient.
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| 7. |
- Lundgren, T.
(author)
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The dynamics of oxygen transport into soil covered mining waste deposits in Sweden
- 2001
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In: Journal of Geochemical Exploration. - 0375-6742 .- 1879-1689. ; 74:1-3, s. 163-173
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Journal article (peer-reviewed)abstract
- One important objective in covering sulphide mining waste deposits with soil layers is to reduce the transport of oxygen to the waste. Irregular, unexpected and significant peaks were recorded in oxygen concentrations in a covered waste rock dump. They initiated a series of internal gas pressure recordings that were carried out in three covered sulphide waste deposits - one tailings impoundment and two waste rock deposits. All are situated in Sweden. Significant pressure variations were found in the covered waste. Sudden changes in ambient air pressure resulted in corresponding variations in the dumps. During periods with stable air pressures, even gravitational pressure variations (tidal effects) were experienced. The amplitude is about half the corresponding external variation. Approximate calculations show that the pressure variations are too low to explain the experienced peaks in oxygen concentration. The pressure recordings have verified that the covers as a whole act as tight barriers and that oxidation of sulphides due to advective transport of oxygen is probably of little importance, at least if the imperfections in the covers are reasonably small. © 2001 Elsevier Science B.V. All rights reserved.
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| 8. |
- Weihed, Pär, 1959-
(author)
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Lithogeochemistry, metal and alteration zoning in the Proterozoic Tallberg porphyry-type deposit, northern Sweden
- 1991
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In: Journal of Geochemical Exploration. - : Elsevier BV. - 0375-6742 .- 1879-1689. ; 42:2-3, s. 301-325
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Journal article (peer-reviewed)abstract
- The Tallberg porphyry-type deposit is situated in the Early Proterozoic, syntectonic Jörn Granitoid Complex (JGC). The occurrence shows similarities with Phanerozoic porphyry type deposits: (a) low grade (0.27% Cu) and large tonnage, 44 × 106 metric tonnes, (b) stockwork as well as disseminated sulphides, (c) hydrothermal propylitic and phyllic alterations, (d) sulphides spatially associated to tectonic lineaments, and (e) genetically related to granitoid porphyry stocks. Lithogeochemical investigations indicate a metal zonation with (Mo+Cu+S) → (Zn+Pb±Au) → (As) from centre outwards. The host granitoid shows similarities with modern I-type granitoids, and the high primary content of Cu and Fe is possibly a discriminant factor for exploration for similar porphyry-type occurrences in Early Proterozoic volcanic arc terrains. Late shear zones adjacent to postmineral dykes have high Au contents (2-3 g/t), which are interpreted as gold mobilized from the porphyry-type deposit.
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| 9. |
- Alvarellos, Federico, et al.
(author)
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Geochemical and mineralogical characterization of acid sulfate soils in Luleå, northern Sweden
- 2024
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In: Journal of Geochemical Exploration. - : Elsevier B.V.. - 0375-6742 .- 1879-1689. ; 265
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Journal article (peer-reviewed)abstract
- Acid sulfate soils (AS-soils) are a common feature along coastlines in many countries that can have significant environmental and economic impacts. AS-soils oxidation may cause soil and water acidification, the release and mobilization of metals and the formation of new precipitated phases. In northern Sweden, some soils are already oxidized and constitute an environmental concern. This study aimed to analyze the geochemistry and mineralogy of AS-soils profiles by identifying element depletion and accumulation zones, the parent material, minerals that contribute to acidity and their oxidation products as well as anomalous element content values that could be related to anthropogenic sources. Two soil profiles were drilled close to the Lule River in Södra Sunderbyn, Luleå. The profiles were characterized by an oxidized zone (OZ) with a declining trend in element content, a transition zone (TZ) where elements tended to accumulate and a reduced zone (RZ) where elements had their maximum content. The pH was a key determinant of the element distribution. Cadmium, Co, Ni and Zn were found to be typical elements released into the environment during AS-soils oxidation. After sample incubation, pH measurements showed a pronounced decrease in layers with higher S and total organic carbon (TOC) content. Both profiles developed a larger thickness of potential acid-risk sediments according to S, TOC and pH measurements during incubation. Iron sulfides were identified as the main acidity generators, represented by an abundance of framboidal pyrites with a Mn-rich rim formed under anoxic-euxinic conditions. Iron sulfates and iron oxyhydroxides (FeOOH, FeOH3) were identified as the most common products of oxidation processes.
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| 10. |
- Antelo, Juan, et al.
(author)
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Stability of naturally occurring AMD–schwertmannite in the presence of arsenic and reducing agents
- 2021
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In: Journal of Geochemical Exploration. - : Elsevier. - 0375-6742 .- 1879-1689. ; 220
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Journal article (peer-reviewed)abstract
- Secondary iron oxides formed in acid mine drainage, such as schwertmannite, are scavengers for metal(loid)s in mining environments. Increasing the understanding of the geochemical transformations of these minerals, as well as knowing how metal(loid)s affect these transformations, is crucial to ultimately predict the fate of these trace elements in acidic mine drainage and to minimize the potential environmental risk. In this study, transformation experiments have been conducted with a schwertmannite-rich sediment collected from a mining area and with synthesized schwertmannite as a reference material. The transformation of schwertmannite into goethite was studied as a function of the presence of arsenic, pH value, and redox conditions. Arsenic delayed the mineral transformation from pseudo-stable amorphous phases to more stable crystalline forms, especially at higher arsenic loadings and more acidic pH. Experiments in the presence of Fe(II) and ascorbic acid have proven that both components promote the mineral transformation or reductive dissolution of schwertmannite under anoxic conditions. The presence of arsenic reduced the catalytic effect of Fe(II), stabilizing the schwertmannite particles. On the other hand, arsenic had no effect on the reductive dissolution at these conditions when ascorbic acid was used as a reducing agent. © 2020 Elsevier B.V.
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