Showing papers in "Applied Earth Science in 2004"
TL;DR: Antimony and arsenic are potentially toxic in the environment when dissolved in water at low levels (<0·01 mg/l) as mentioned in this paper, and they are commonly mobilised into the environment from mesothermal mineral deposits.
Abstract: Antimony and arsenic are commonly mobilised into the environment from mesothermal mineral deposits. Both these metalloids are potentially toxic in the environment when dissolved in water at low levels (<0·01 mg/l). Mobility of antimony, in comparison to that of arsenic, is documented at mine sites in four different mesothermal systems in low grade Palaeozoic-Mesozoic metamorphic terranes of New Zealand (Globe Hill, Reefton; Macraes, Otago; and Endeavour Inlet, Marlborough) and Australia (Hillgrove, New South Wales). Dissolved antimony can reach ~50 mg/kg in mine waters where evaporative concentration occurs in oxidised near-neutral pH mine waters in contact with stibnite. Such waters are chemically saturated with respect to antimony oxides, and antimony oxide precipitation occurs locally. Most mine waters have lower dissolved Sb concentrations, especially where high rainfall causes dilution. However, high rainfall areas have widespread diffuse mobilisation of both Sb and As to give elevated backgr...
65 citations
TL;DR: A stream sediment geochemical survey was undertaken in the extreme north-west of Zambia with three primary objectives: (i) to provide a baseline environmental database for an area uncontaminated by heavy industry, mining and intensive farming; (ii) to detect metal anomalies that may indicate potentially economic mineral deposits; and (iii) providing a tightly controlled geochemical database that can be used as a standard for future mineral exploration programmes throughout central Africa as discussed by the authors.
Abstract: A stream sediment geochemical survey was undertaken in the extreme north-west of Zambia with three primary objectives: (i) to provide a baseline environmental database for an area uncontaminated by heavy industry, mining and intensive farming; (ii) to detect metal anomalies that may indicate potentially economic mineral deposits; and (iii) to provide a tightly controlled geochemical database that can be used as a standard for future mineral exploration programmes throughout central Africa. Three major geological domains underlie the studied area. These are crystalline Neoarchaean to Palaeoproterozoic basement, an overlying sequence of Neoproterozoic Katanga strata within the western part of the Lufilian Arc (a Pan African orogenic belt that hosts major copper‐cobalt deposits in the Central African Copperbelt of northern Zambia and the Democratic Republic of Congo [DRC]), and extensive Caenozoic Kalahari Group sediments. Stream sediments collected from each of the three geological domains have distinctive geochemical signatures. Relatively high values for a range of elements including uranium, thorium and yttrium were found in stream sediments within the pre-Katanga basement domain. Enhanced values of a larger number of elements are present in the stream sediments underlain by Katanga strata including significant, previously unknown, copper anomalies that warrant detailed follow-up work. The high metal values in sediments derived from Katanga strata contrasts sharply with sediment samples collected from drainage channels in areas of thick Kalahari sand, which mostly have very low values of all analysed elements. Our results suggest that it will be difficult to detect contamination of streams in the Copperbelt areas of Zambia and the Democratic Republic of Congo due to their naturally high metal concentrations. By contrast, it will be relatively easy to monitor pollution of areas underlain by Kalahari sands as these have naturally very low values of all elements.
26 citations
TL;DR: In this paper, the environmental behavior of metals from tailings in a branch of the Taxco river was investigated, and the results showed that metals are released from the tailings as a result of sulphide oxidation and rain-water erosion.
Abstract: Mining in Mexico has produced important economic benefits since pre-Hispanic times. On the other hand, tailings and rock wastes constitute potential pollution sources in many zones of the country. Taxco, about 150 km south-west of Mexico City, is one of the historical mining zones of Mexico. The environmental behaviour of metals from tailings in a branch of the Taxco river was investigated. Several communities use the Taxco river water along its flow. Samples were taken from tailings, river-waters and sediments. Field determinations included conductivity, pH, Eh, temperature and alkalinity of the water. Mineralogical and chemical analyses were performed in tailings and sediments. Water analyses included main ions, and metals in acidified filtered and unfiltered samples. Quartz, jarosite, pyrite, chalcopyrite, Fe oxihydroxides, gypsum, clay and silica minerals were identified in the tailings. All samples had an acid pH (2·50‐4·16) and high concentrations of Pb (up to 2750 mg/kg), Zn (up to 690 mg/kg) and As (up to 3530 mg/kg). Mineralogical and chemical characteristics of tailings indicated occurrence of sulphide oxidation. Higher metal concentrations were found in unfiltered, acidified water samples than in filtered water samples in the year 2000: Fe (up to 21·2 mg/l), Zn (up to 13·4 mg/l) Pb (up to 0·115 mg/l) and As (up to 0·035 mg/l). Zn, Fe and Pb reached much higher concentrations in the dry season than in the rainy season. The Taxco river water does not comply with Mexican drinking water standards. High concentrations of Pb (up to 5280 mg/kg) and Zn (up to 33,500 mg/kg) were measured in sediments. Pb and Zn in sediments accumulated downflow in the dry season. A more uniform distribution was found in the rainy season. Results showed that metals are released from tailings as a result of sulphide oxidation and rain-water erosion. Metals are then transported by the river-water mainly in particulate form and, after settling, increase the concentration of metals in the sediments.
22 citations
TL;DR: The Mount Pleasant Sn-W-Mo deposits occur within the margin of an eroded caldera underlain by a Devono-mississippian intrusive-subvolcanic-eruptive complex of granitic, porphyritic and felsic pyroclastic rocks as discussed by the authors.
Abstract: The Mount Pleasant Sn–W–Mo deposits occur within the margin of an eroded caldera underlain by a Devono–Mississippian intrusive-subvolcanic-eruptive complex of granitic, porphyritic and felsic pyroclastic rocks. The separate North and Fire Tower mineralised zones are centred in volcanic necks defined by hydrothermal breccias within this complex. The oldest of three successive granites in both Zones hosts W–Mo mineralisation, whereas the two younger granites in the North Zone contain various Sn deposits. One of these, the endogranitic tin zone, is an irregular but generally tabular body hosted within a distinctive, highly evolved phase of the third, and youngest granite.The endogranitic tin zone was formed by successive stages of sericitisation, chloritisation/topazification-silicification, brecciation, dense chloritisation-topazification and late replacement. It contains quartz, chlorite, topaz, fluorite, cassiterite, arsenopyrite, base metal sulphides, pyrite, stannite, wolframite, native bismuth,...
19 citations
TL;DR: In this article, a systematic sampling of the river Odiel was performed several times during the year with the analysis of water flux and metal concentration data from the Odiel for the last 20 years.
Abstract: The river Odiel drains the central part of the Iberian Pyrite Belt, one of the oldest and most important sulphide mining districts of the world. Mining activities in the Odiel watershed started in the third millennium BC, and have continued until now with minor interruptions. As a consequence of this long mining history, large amounts of sulphides and sulphide-rich residues have been exposed in the surface. The oxidation of these sulphides has produced acidic effluents very rich in sulphate, metals and metalloids that end in the river Odiel. As a result, the water in the lower part of the river has a pH lower than 3.5. The amount of water transported by the river Odiel has important oscillations during the year. In order to understand the transport of pollutants in this river, we have combined a systematic sampling of the river several times during the year with the analysis of water flux and metal concentration data from the river Odiel for the last 20 years. With this long-term database, the cal...
17 citations
TL;DR: The Global Zinc Project as mentioned in this paper was developed by Pasminco Australia Ltd to provide a world view of zinc mineralisation and a methodology to prioritise geological provinces for exploration and the discovery of potentially economic ore deposits.
Abstract: The Global Zinc Project was developed by Pasminco Australia Ltd to provide a world view of zinc mineralisation and a methodology to prioritise geological provinces for exploration and the discovery of potentially economic ore deposits. The project grew in response to increasing risk from falling global discovery rates, maturing of exploration terranes in traditional areas, and the uncertainties of quantifying the risks for mineral investment in newly emergent countries. Components of the project involved the digital integration of a global mineral occurrences database, delineation of zinc provinces, ore deposit models, reverse economic studies, plate tectonic reconstructions and country risk analysis. The data were analysed in two separate modules. The Prospectivity Rating Module provides a quantitative comparison between the observed geology of a province and the mappable features of ore deposit models. It ranks the prospectivity of a province for the potential occurrence of one or more orebodies...
15 citations
TL;DR: In this paper, the authors examined several drawbacks and limitations of indicator kriging applied to continuous variables, in the scope of the lognormal random function model, focusing on precision problems, inconsistencies of the results when one sample is added or removed, and biases generated by the post-processing steps (tail extrapolation and change of support).
Abstract: This paper examines several drawbacks and limitations of indicator kriging applied to continuous variables, in the scope of the lognormal random function model. In particular, it focuses on precision problems, inconsistencies of the results when one sample is added or removed, and biases generated by the post-processing steps (tail extrapolation and change of support) and by the use of a non-bias condition in the kriging system. The selectivity of the local distributions is shown to be systematically overestimated when performing a change of support based on the global variance reduction factor, and underestimated when using an ordinary kriging instead of a simple kriging. This situation may lead to strong biases in the evaluation of the resources and reserves in ore deposits. To solve the change-of-support problem, a local variance reduction factor is given for the lognormal case; the proposed approach may be generalised to other models so as to improve the estimates.
12 citations
TL;DR: In this paper, a 1D transport and reaction model based on a hydraulic 3-D model of the study area is developed and tested in an aquifer which already is contaminated by acid mine drainage.
Abstract: Most of the former East-German open cast lignite mines were shut down. To mine the lignite, the ground water table had been lowered up to 100 m. Today, the ground water flow regimen is changing due to the refilling of the depression cones and subsurface acid mine drainage is endangering surface waters and drinking water supply facilities outside the mining areas. Because of the large discharge area, only in situ technology can be used to reduce acid mine drainage. It has been developed on a laboratory scale and is currently being tested in an aquifer which already is contaminated by acid mine drainage. Sulphate reduction and the formation of sulphide minerals are being enhanced by adding bioreactive liquids in the aquifer. To apply the remediation technology to other areas which will soon be endangered, their future ground water quality is being assessed by predictive modelling. A 1-D transport and reaction model based on a hydraulic 3-D model of the study area is being developed. The dump materia...
11 citations
TL;DR: In this paper, the dramatic variations in stream-sediment chemistry that occur over some large areas of superficially homogeneous geology are discussed. But their interpretation may be based on assumptions of relative compositional uniformity within broad categories of bedrock lithology.
Abstract: Stream-sediment geochemistry is commonly used to provide a regionally averaged, background composition against which may be judged the anomalies caused by unusual geology, mineralisation or pollution. Its interpretation may be based on assumptions of relative compositional uniformity within broad categories of bedrock lithology. This approach is undermined by the dramatic variations in stream-sediment chemistry that occur over some large areas of superficially homogeneous geology. In these cases, regional geochemistry may pickout subtle compositional variations in bedrock that are not otherwise apparent. Thick greywacke sequences present a particular problem of geological interpretation by virtue of their general uniformity, with a good example provided by the Southern Uplands terrane. There, some stratigraphical variations in greywacke composition, reflecting changes in sedimentary provenance, are known from petrographic and analytical work but are not visible macroscopically. However, contoured ...
10 citations
TL;DR: In this paper, the authors characterise the evolution trends and geochemical features of the Khangilay pluton and the Orlovka and Spokoinoe deposits and study the genesis of the three granite massifs by examining fluidrock and crust-mantle interaction in the evolution of granitoid magmatism.
Abstract: Element concentrations and Pb isotope data are reported for the Khangilay, Orlovka and Spokoinoe granite massifs and their host rocks in the Orlovka–Spokoinoe mining district, Eastern Transbaikalia, Russia. The aim of the paper is to characterise the evolution trends and geochemical features of the Khangilay pluton and the Orlovka and Spokoinoe deposits and to study the genesis of the three granite massifs by examining fluid–rock and crust–mantle interaction in the evolution of granitoid magmatism. Zr/Hf, Y/Ho and Rb/Sr demonstrate that all three granite bodies show a continuous fractionation history from parental biotite–muscovite granites of Khangilay to highly evolved ore-bearing amazonite granites of Orlovka. Khangilay and its derivates Spokoinoe and Orlovka represent different evolution stages. REE patterns of the amazonite granites of Orlovka show a stronger Eu anomaly and more apparent REE tetrad effects in comparison with the less evolved granites of Khangilay. Pb isotope analyses indicate...
10 citations
TL;DR: A legacy from mid-19th century mining near Newtownards is lead-rich tailings and derived soils containing typically 10% Pb as discussed by the authors, where lead occurs dominantly as very fine-grained cerussite (PbCO3) and calcite and dolomite.
Abstract: A legacy from mid-19th Century mining near Newtownards is lead-rich tailings and derived soils containing typically 10% Pb. Lead occurs dominantly as very fine-grained cerussite (PbCO3) and the tailings are also rich in calcite and dolomite. Rainwash and overland flow has transferred tailings material from the original impoundments into a meadow, forming a depositional 'plume' characterised by contrasting soil colour, vegetation species and vigour of growth. Cerussite is dispersed farther than calcite and dolomite. In areas of the plume proximal to the tailings source, the Pb content (dry weight) of dock and plantain is up to 6540μg/g in roots and 1140μg/g Pb in leaves. Plume soils and plants are also enriched in Fe, Mn, Cu, Zn, Cd and Sb. Bracken foliage contains up to 1500μg/g Pb in non-tailings soil and 2800μg/g Pb in tailings-contaminated soil. For most elements analysed, there is a low contrast between bracken plants growing on tailings-contaminated and normal soil. This reflects the low bio...
TL;DR: In this article, the concentrations of rare earth elements (REEs) in an acidic fresh groundwater of a coastal plain sand aquifer in south-eastern Nigeria were analyzed and compared with reported concentrations in the literature for other areas.
Abstract: This study documents the concentrations of rare earth elements (REEs) in an acidic fresh groundwater of a coastal plain sand aquifer in south-eastern Nigeria. The aim was mainly to determine the concentrations, patterns, and probable source of REEs and to compare the REE data with reported concentrations in the literature for other areas. The results show that the concentrations of the sum of the REEs are generally less than the values in the literature for some natural fresh groundwaters, saline groundwaters and contaminated waters. The groundwaters are enriched in the middle REEs (MREEs) compared to the light REEs (LREEs) and heavy REEs (HREEs). The enrichment is attributed to secondary Al-rich mineral phases associated with the aquifer and dissolution by acidic water of Fe rich inorganic particulates and/or Fe-rich surface coating on particulates. The source of the REE signatures is related to the rocks of the adjoining areas based on similar Ce anomaly pattern in the groundwater and the source...
TL;DR: The Global Mineral Occurrences Database (GMOD) as discussed by the authors is a database built by Pasminco Australia Ltd to cover zinc mineral occurrences over the entire globe and contains over 14 000 records of which 1700 contain resources information.
Abstract: This paper presents an analysis of the Global Mineral Occurrences Database (GMOD), a zinc deposits database built by Pasminco Australia Ltd to cover zinc mineral occurrences over the entire globe. The database contains over 14 000 records of which 1700 contain resources information. A resource is taken as the total in-ground resource, including past production and current resources. An economic resource classification has been applied to all deposits with resources which divides them into four categories, high grade zinc deposits, low grade zinc deposits, deposits where Cu–Au is economically more significant than Zn–Pb–Ag and minimum grade zinc deposits. Analysis of the data shows that the total world endowment of zinc metal, defined in resources, is over 881 Mt. North America has the greatest endowment of zinc metal and the most deposits. Africa has the least. Canada, the US, China and Australia are the best endowed countries with Australia having larger and higher grade deposits. The Palaeoprote...
TL;DR: In this article, the potential for stratiform massive sulphide mineralisation in two parts of south-west England, the Central Area between Bodmin Moor and Dartmoor, and North Devon, was assessed.
Abstract: This study provides an assessment of the potential for stratiform massive sulphide mineralisation in two parts of south-west England, the Central Area between Bodmin Moor and Dartmoor, and North Devon. The Central Area was selected on the basis of its tectonic, stratigraphical and lithological similarities with the Iberian Pyrite Belt (IPB) where numerous volcanogenic massive sulphide (VMS) deposits occur. North Devon is considered prospective on account of its similarities to the Harz Massif in Germany that hosts the major polymetallic sedimentary exhalative (Sedex) deposit at Rammelsberg. More than 60 stratiform mineral occurrences are known in the two areas and previous exploration, including extensive drainage geochemical surveys, geophysical surveying and drilling, has revealed stratiform mineralisation at some localities, including at Egloskerry, near Bodmin Moor, where up to 10% Pb over 4·5 m was recorded. In North Devon, stratiform mineralisation has been recorded from a borehole at Honeym...
TL;DR: The base-metal sector of the high-sulphidation epithermal deposit of Kirki (St Philippe) was occasionally mined during the period 1973-1998, without strict environmental management as discussed by the authors.
Abstract: The base-metal sector of the high-sulphidation epithermal deposit of Kirki (St Philippe) was occasionally mined during the period 1973–1998, without strict environmental management. The mineralisation shows a significant content of polluting elements. Mineralogical investigations indicate a very low degree of sulphide alteration. Sphalerite and galena concentrates were produced by conventional flotation techniques. Mine excavation wastes and flotation tailings were dumped and exposed to weathering. Waters draining downstream of the mine waste dump are near neutral. Acid mine waters forming a pit lake are highly polluted. Evapoconcentration of the pit lake waters leads to the generation of a toxic mineral precipitate on the open pit floor, comprising soluble secondary salts. The paper concludes with a consideration of the remedial measures required.
TL;DR: The Nalunaq gold deposit as mentioned in this paper is a mesothermal vein-type gold deposit, hosted in amphibolitefacies metamorphosed mafic rocks in the Nanortalik district in South Greenland.
Abstract: The Nalunaq deposit is a shear-zone hosted gold deposit, characterised by high grades (up to 5240 g/t Au over 0˙8 m). The host rocks are Palaeoproterozoic metamorphosed mafic rocks in the Nanortalik district in South Greenland. As a generic type, the Nalunaq gold mineralisation is a mesothermal vein-type gold deposit, hosted in amphibolitefacies metamorphosed mafic rocks. The gold is associated with sheeted quartz veins, hosted in a large-scale shear structure, which appears to relate to regional thrusts. They vary in width between 0˙05 m and 1˙8 m and form a relatively continuous structure. However, possibly due to extensive post-mineralisation deformation, there is no simple relationship between gold grade and thickness of the quartz veins. Eight samples were examined from amphibolites (host rock), quartz veins and amphibolites cut by quartz veins. The mineralisation is a low-S system, and consists mainly of pyrrhotite, lollingite, pyrite, arsenopyrite, chalcopyrite, gold and electrum, scarce Bi...
TL;DR: In this paper, the authors assess the negative impact on soil caused by several mining episodes that occurred at Marrancos mine, an old gold/silver mine, and present a method of stochastic simulation as an alternative technique to predict pollutant concentrations of heavy metals, or metalloids, at unsampled locations.
Abstract: The purpose of this study was to assess the negative impact on soil caused by several mining episodes that occurred at Marrancos mine, an old gold/silver mine. The main aims were to: (i) assess the quality of the soil and the delineation of areas potentially contaminated by arsenic; (ii) assess the uncertainty attached to the assignment; and (iii) present a method of stochastic simulation (probability field simulation) as an alternative technique to predict pollutant concentrations of heavy metals, or metalloids, at unsampled locations. Indicator kriging was used to model the uncertainty attached to the concentration values at the unsampled sites and p-field simulation produced probability maps that allowed assessment of the probability that the arsenic concentrations did not exceed a regulatory threshold. The probability maps were then used to identify hazardous areas. About 90 realisations were generated for the variable, meaning 90 equiprobable scenarios for the spatial distribution of arsenic...
TL;DR: In this article, a two-dimensional vertical model was built up using Processing Modflow to quantify the contribution of water oscillations to acidification processes in the flooded lignite mine LOHSA II, and the modelled transient water fluxes were used to estimate the discharge of acid builders from the water saturated part of the heap into the lake.
Abstract: During and after the process of artificial recharge by flooding of former pit mines, oscillations of the water level, caused by seasonal effects or management strategies, are often inevitable. In the study area LOHSA in the new eastern federal states of Germany, the annual water oscillations due to management strategies are predicted to range between 5–8 m. This leads to oxygen input by freshwater and air, which causes pyrite oxidation in the surrounding sediments and leads to additional acidification of both groundwater and the flooded lakes. To quantify the contribution of water oscillations to the acidification processes in the flooded lignite mine LOHSA II, a two-dimensional vertical model was built up using Processing Modflow. The strong lateral migration of the shoreline due to the low morphologic gradient was simulated by the reservoir package. The modelled transient water fluxes were used to estimate the discharge of acid builders from the water-saturated part of the heap into the lake. Th...
TL;DR: Asturias has numerous derelict Hg mine sites as a legacy of a past intensive mining activity, and the most important of these are located in the Caudal River catchment as mentioned in this paper.
Abstract: Asturias has numerous derelict Hg mine sites as a legacy of a past intensive mining activity, and the most important of these are located in the Caudal River catchment. These mines have been abandoned without remediation, and the legacy of these mine works remains currently in the form of mine wastes stocked in piles on the surface. In the exploited ore deposits, As is quite abundant in the form of sulphides (As-rich pyrite), sulpho-arsenides (arsenopyrite, realgar and orpiment), and supergenic minerals (scorodite). Significant quantities of mine and metallurgical wastes stocked at surface in spoil heaps of different age and size, and old galleries and transversals acting as pseudokarstic aquifers, are potential pollution pathways for the spreading of As to the environment. As a consequence of the weathering of As-rich minerals, As contents are high in mine effluents and spoil heap leachates. In the spoil heaps, waste materials are subjected to the action of a humid environment; in consequence, th...