Some features of mineral waters in Russia

 The Russian Federation has many aquifers and these possess a wide range of chemical compositions. In Russia about 300 mineral water sources have been developed as spas and health resorts. More than 150 of them produce bottled mineral water. A brief historical revue is given. The study of mineral waters in Russia began as far back as the reign of Peter the Great (1682–1725). It has been prolonged by works of many Russian scientists. The details of the chemical composition of the different types of Russian mineral waters and some geological aquifer peculiarities are described. The most widely used classification of mineral waters in Russia is presented. The present condition of these waters and the government standards laid down for their use are described. Examples of different mineral waters are given. Received: 14 April 1998 / Accepted: 8 December 1998     

Hydrogeology of limited aquifer in a granitic terrain

 Detailed hydrogeological studies in a granitic micro-watershed have been carried out to determine the extent, behavior, and characteristics of the aquifer. The study includes analysis of lithologs, drill time log, pumping tests, and slug tests. Realistic field conditions have been taken into account for characterizing the aquifer system. Slug tests were carried out to estimate aquifer parameters at the wells which could not sustain pumping. Received: 20 November 1997 · Accepted: 23 February 1998     

State of the art of modelling two-phase flow in fractured rock

 Two-phase flow in fractured rock is an important phenomenon for a range of practical problems, not the least of which is non-aqueous phase liquid (NAPL) contamination of groundwater. Although multiphase systems have long been studied in the petroleum field, in the hydrogeological field progress has only just reaches the point where models are being developed. Scale effect is one of the main issues of concern. Although models presented in this paper have the potential to provide useful predictions, they can only be used to investigate a variety of possible scenarios with parameters being specified in the form of distribution of values. The calibration and validation of all but the simplest of these models poses a formidable task, with great demands on hydrogeologists and geophysicists to provide adequate data. Received: 20 May 1996 · Accepted: 19 August 1996     

The relationship between the water table and the surface flow of a losing stream, lower Medano Creek, Great Sand Dunes National Monument, Colorado

 Proposed groundwater withdrawals in the San Luis Valley of Colorado may lower the water table in Great Sand Dunes National Monument. In response, the National Park Service initiated a study that has produced a generalized conceptual model of the hydrologic system in order to assess whether a lowering of the water table might decrease the surface flow of lower Medano Creek. Based upon information obtained during the drilling of several boreholes, there appear to be five important hydrostratigraphic units underlying lower Medano Creek within the upper 30 m of the ground surface: 1. a perched aquifer overlying an aquitard located between about 5 and 6 m below the ground surface; 2. the aquitard itself; 3. an unconfined aquifer located between the upper and lower aquitards; 4. an aquitard located between about 27 and 29 m below the ground surface; and 5. a confined underlying the lower aquitard. Because the areal extent of the aquitards cannot be determined from the borehole data, a detailed conceptual model of the hydrogeologic system underlying lower Medano Creek cannot be developed. However, a generalized conceptual model can be envisioned that consists of a complex system of interlayered aquifers and leaky aquitards, with each aquifer having a unique hydraulic head. Water levels in the perched aquifer rise rapidly to their annual maximum levels in response to the arrival of the flow terminus of Medano Creek during the spring runoff event, and the location of the flow terminus is directly dependent upon the discharge of the creek. Water levels in the deeper, non-perched aquifers do not appear to fluctuate significantly in response to the arrival of the flow terminus, demonstrating that it is unlikely that the proposed groundwater withdrawals will decrease the surface flow of lower Medano Creek. Received: 27 December 1995 · Accepted: 20 February 1996     

A comparison of electrical and electromagnetic methods for the detection of hydraulic pathways in a fractured rock aquifer,Clare Valley,South Australia

Within fractured rock, the irregular and often unpredictable distribution and geometry of hydraulically conductive fractures produces large spatial variations in bore yield and groundwater quality. As fractures act as conduits for flow of both groundwater and electrical charge, methods which can efficiently detect the distribution of electrical pathways can be used to infer characteristics of significant hydrological parameters. This study compares the capabilities and limitations of electrical data obtained from direct current (DC) and electromagnetic (EM) surface azimuthal measurements, and from DC borehole-to-surface and cross-borehole measurements, for the interpretation of major hydrological structures in Clare Valley, South Australia. Electrical and EM surface methods are limited by poor depth sensitivity and the presence of conductive overburden, but provide useful tools for determining directional variations in resistivity at sites lacking bedrock exposure and boreholes. Application of borehole-to-surface methods yielded a better-resolved interpretation of sub-vertical fracture strike and was useful in identifying lateral variations in bedrock heterogeneity. Improved flexibility and sensitivity to measurements at depth permitted cross-borehole electrical tomography data to be used in reconstructing the spatial distribution of sub-horizontal, laterally extensive, electrically conductive zones. While the technique is restricted to small-scale sites with multiple boreholes, inferences can be made on fluid connections over a much larger regional scale. It is important to note, however, that while electrical methods provide valuable information about in-situ hydraulic pathways, they do not provide a complete hydraulic characterisation. Such a task requires integration of surface and borehole geophysics, geologic mapping, sampling and pumping tests of wells with packed-off intervals.

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Resumen La geometría, y con frecuencia impredecible, distribución irregular de fracturas hidráulicamente conductivas dentro de roca fracturada genera variaciones espaciales grandes en producción de pozos y calidad de agua subterránea. Debido a que las fracturas actúan como conductos de flujo de agua y carga eléctrica, los métodos que detectan eficientemente la distribución de trayectorias eléctricas pueden utilizarse para inferir las características de parámetros hidrológicos significativos. Este estudio compara las capacidades y limitaciones de datos eléctricos obtenidos de mediciones azimutales superficiales electromagnéticas (EM) y de corriente directa (DC), y de mediciones de DC realizadas en la superficie y pozos así como mediciones realizadas entre pozos para la interpretación de estructuras hidrológicas principales en el Valle Clare, sur de Australia. Los métodos superficiales eléctricos y EM están limitados por sensitividad de profundidad pobre y la presencia de cubierta conductiva, pero aportan herramientas útiles para determinar variaciones direccionales de resistividad en sitios que carecen de pozos y afloramientos rocosos. La aplicación de métodos superficiales y de pozos aportan una mejor interpretación del rumbo de fracturas sub-verticales y fue útil en identificar variaciones laterales en la heterogeneidad del macizo rocoso. El mejoramiento de flexibilidad y sensitividad en las mediciones profundas permitió que los datos de tomografía eléctrica de los pozos fuera utilizado en la reconstrucción de la distribución espacial de zonas eléctricas conductivas, sub-horizontales y lateralmente extensas. Aunque la técnica está restringida a sitios de pequeña escala con múltiples pozos, puede realizarse inferencias sobre relaciones entre fluidos en una escala regional mucho más grande. Sin embargo, es importante notar que aunque los métodos eléctricos aportan información valiosa acerca de las trayectorias hidráulicas in-situ, aún no proporcionan una caracterización hidráulica completa. Esta tarea requiere integrar geofísica superficial y de pozos, mapeo geológico, muestreo y pruebas de bombeo en pozos con intervalos sin empaque.

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Résumé Au sein des roches fracturées, lirrégularité et limprédictible distribution et géométrie des fractures par lesquelles sécoulent leau souterraine produit de larges variations spatiales entre les débits des forages et les paramètres de la qualité de leau. Comme les fractures conduisent et leau et les charges électriques, les méthodes qui peuvent de manière efficiente détecter la distribution des courants électriques peuvent être utilisées pour analyser les caractéristiques des principaux paramètres hydrologiques. Cette étude compare les capacités et les limites des données produites par Courant Direct (DC en Anglais) et par mesure Electromagnétique azimutale de surface (EM en Anglais), et par DC entre surface et forage et entre plusieurs forages, pour linterprétation de la structure hydrologique de la Vallée de Clare, Australie du Sud. Les méthodes électriques et électromagnétiques sont limitées par la faible sensitivité à la profondeur et la présence dune couverture conductrice, mais procure des outils utiles pour déterminer les variations directionnelles en terme de résistivité là où la roche nest pas affleurante et dans les puits. Lapplication de la méthode dinvestigation «forage à surface» apporte une meilleure interprétation des fractures sub-verticales et des hétérogénéités latérales. Les tomographies électriques entre forage bénéficient de la flexibilité et de la sensibilité des mesures en profondeur, et permettent de délimiter lextension latérale des hétérogénéités sub-horizontales de zones conductrices. Alors que la technique est restreinte à de petits sites comprenant de nombreux forages, il est possible de reconstituer les connections hydrauliques à des échelles régionales. Il est important de noter que les méthodes fournissent des informations intéressantes mais pas des caractérisations hydrauliques complètes. Pour cela les données pourraient être complétées par des études plus poussées intégrant les différentes prospections géophysique, les données des cartes géologiques, des échantillonnages et des essais de pompage à différents intervalles de profondeur.

     

Influence of groundwater on the degradation of irrigated soils in a semi-arid region, the inner delta of the Niger River, Mali

The problem of soil degradation through alkalinization/salinization in an irrigated area with a semi-arid climate was examined in the inner delta of the Niger River, Mali, by the study of groundwater hydraulics and hydrochemistry in an area recharged by irrigation water. On the basis of data analysis on various scales, it is concluded that the current extent of the surface saline soils is due to a combination of three factors: (1) the existence of ancient saline soils (solonchaks) resulting from the creation of a broad sabkha west of the former course of the Niger River, now called the Fala of Molodo. These saline crusts were gradually deposited during the eastward tilting of the tectonic block that supports the Niger River; (2) the irrigation processes during the recent reflooding of the Fala of Molodo (river diversion in 1950). These used very poorly mineralized surface water but reintroduced into the alluvial groundwater system – generally of a low permeability (K=10–6?m?s–1) – salts derived from the ancient solonchaks; and (3) the redeposition of the dissolved salts on the surface due to the intense evapotranspiration linked to the present Sahelian climate. In this context, only efficient artificial draining of subsurface alluvial groundwater can eliminate most of the highly mineralized flow and thus reduce the current saline deposits.     

Olocenic alluvial aquifer of the River Cornia coastal plain (southern Tuscany, Italy): database design for groundwater management

 Hydrogeological research is in progress, utilizing GIS methods, with the principal aim of modelling the Olocenic alluvial aquifer of the River Cornia coastal plain (southern Tuscany, Italy), which has been exploited for drinking water, irrigation, and industrial uses. A consequence of exploitation has been the appearance of wide seawater intrusion. The alluvial aquifer has recently been subjected to new well fields for the supply of drinking water, with an increase of total average discharge of about 4×10⁶ m³/year. This paper presents results obtained from updating and integrating basic knowledge and structuring the database. The hydrogeological study allowed the recognition of the extension of areas that are characterized by a hydraulic head under the sea level, the progressive salinization of the aquifer, and the increase of water deficit in the aquifer which is produced by a progressive extraction of water superior to the natural recharge. In addition, benefits and disadvantages resulting from the location of new well fields in a hydrogeologically favourable zone, and the boundary conditions for much of the area studied have been defined. The GIS was used as support for making and updating the tabular and spatial database with the aim of integrating the local and regional hydrogeological knowledge. This study will permit the realization of a numerical simulation of the groundwater flow of the aquifer aimed at correcting the management of water resources, by means of the GIS-modelling integration. Received: 23 June 1998 · Accepted: 16 November 1998     

Hydrogeology and geochemistry in the Curuksu (Denizli) hydrothermal field, western Turkey

 Curuksu is a low temperature hydrothermal system located within the upper sector of the B. Menderes Graben. The hydrologic structure of the Curuksu hydrothermal system is largely controlled by major graben faults where it is characterized by the presence of two thermal reservoirs. One is formed by Paleozoic quartzite, schist and marble units, and the second consists of Pliocene limestone-travertine units. The thermal conditions in the Curuksu region indicate that the regional tectonics and resulting local stress field control low temperatures activity. Temperatures of 30 springs emerging in the study area range between 15 and 55  °C. These springs are classified as cold fresh, warm mineral and thermal waters. Pamukkale, Karahayıt and Honaz springs are steam condensate waters, whereas Curuksu springs are commonly steam-heated waters with respect to the major anion concentrations. The reservoir temperatures have been estimated from chemical compositions by utilizing simultaneously, geothermometers and mixing models. According to these thermometric methods, the most probable subsurface temperature is in the range of 62–90  °C. However, the mixing models suggest a temperature level of 80  °C for the parent water. The system has low total dissolved solid (TDS) of ∼1000–1500 mg/l, which indicate that these waters undergo conductive cooling within the reservoir. Received: 9 September 1999 · Accepted: 14 February 2000     

Fracture pattern and electrical resistivity studies for groundwater exploration

 The occurrence, movement and control of groundwater, particularly in hard-rock areas, are governed by different factors such as topography, lithology, structures like fractures, faults and nature of weathering. An attempt is made in the present study to investigate the extent of the influence of structures such as fractures and thereby delineate the nature of subsurface lithology with the help of an electrical resistivity method. For this study, the Upper Gunjanaeru River basin, Cuddapah district Andhra Pradesh was chosen to determine groundwater potentials. In order to understand the significance of the fracture pattern, geological, hydrogeomorphological and lineament maps were prepared based on the field data and also from the LANDSAT TM imagery. Further, electrical resistivity surveys were conducted to determine the subsurface lithology and also to confirm the studies of LANDSAT imagery. The isoresistivity contour map has been prepared based on the 45 VES conducted to determine the resistivity variations in the study area. The isoresistivity contours obtained were found to conform to the structural trends obtained by geological studies and also confirm the relationship between the structure and secondary porosity present in the rocks. The lineaments in the area have two preferred directions. One set is a NE-SW direction (N 30°–70° E; S 30°–70° W) and another is a NW-SE direction (N 0°–30° W; S 0°–30° E and N 60°–80° W; S 60°–80° E). The water-table contour map shows that the direction of groundwater flow is south to north. Received: 3 March 1997 · Accepted: 17 June 1997     

Development and testing of a contamination potential mapping system for a portion of the General Separations Area, Savannah River Site, South Carolina

 A methodology was developed to evaluate and map the contamination potential or aquifer sensitivity of the upper groundwater flow system of a portion of the General Separations Area (GSA) at the Department of Energy's Savannah River Site (SRS) in South Carolina. A Geographic Information System (GIS) was used to integrate diverse subsurface geologic data, soils data, and hydrology utilizing a stack-unit mapping approach to construct mapping layers. This is the first time that such an approach has been used to delineate the hydrogeology of a coastal plain environment. Unit surface elevation maps were constructed for the tops of six Tertiary units derived from over 200 boring logs. Thickness or isopach maps were created for five hydrogeologic units by differencing top and basal surface elevations. The geologic stack-unit map was created by stacking the five isopach maps and adding codes for each stack-unit polygon. Stacked-units were rated according to their hydrogeologic properties and ranked using a logarithmic approach (utility theory) to establish a contamination potential index. Colors were assigned to help display relative importance of stacked-units in preventing or promoting transport of contaminants. The sensitivity assessment included the effects of surface soils on contaminants which are particularly important for evaluating potential effects from surface spills. Hydrogeologic/hydrologic factors did not exhibit sufficient spatial variation to warrant incorporation into contamination potential assessment. Development of this contamination potential mapping system provides a useful tool for site planners, environmental scientists, and regulatory agencies. Received: 1 April 1997 · Accepted: 4 November 1997     

Assessment of morphometric parameters of Greek Rhone-type deltas. Hydrogeologic and environmental aspects

 The morphometric characteristics and some features concerning the local conditions of three Rhone-type Greek deltas are considered, summarized and correlated. They both express the deltaic internal lithologic structure and the configuration of the coast lines and subaqueous profiles. Despite the existing differences, concerning the lithologic structure, the coastline shape and the subaqueous profile, the Rhone type deltas maintain their principal characters and their basic configuration of the deltaic prominence. The above-mentioned differences are mainly due to local conditions which, as epigenetic factors, affect the distribution of transported material and complete the classification and deposit action of marine mechanisms, mainly the wave action and sea currents. The totality of these factors determined the continental and subaqueous structure of the deltas, which is related to the environmental and hydrogeological aspects presented in this paper. Received: 19 May 1998 · Accepted: 15 September 1998     

Weathered bedrock as a source of sand and gravel aggregate in north-eastern New South Wales, Australia

 The most commonly recognized sources of sand and gravel aggregate are the deposits of coastal, fluvial and glacial sedimentary processes. It is not commonly recognized that weathered bedrock is also an important source of sand and gravel aggregate. In the case of weathered sedimentary bedrock the product may be indistinguishable from modern sedimentary materials and deposits may be misidentified. Batson's quarry is a major sand and gravel aggregate resource for the rapidly developing region of north-eastern New South Wales. The deposit has previously been assumed to be a young sedimentary deposit, but detailed field examination and comparison with surrounding rock types indicates that it has formed from weathered Mesozoic sandstone bedrock. The extraction of weathered bedrock aggregate deposits has distinctive environmental implications because, unlike sedimentary aggregates, they are not restricted by the geometry of sedimentary environments and do not necessarily interfere with surface drainage systems. This study shows that the recognition of the geological origin of a resource is essential in order to determine its potential geographical extent, and thereby maximize its utilization and minimize land use conflict. Received: 3 January 1996 / Accepted: 1 November 1996     

Belogubite,a New Mineral of the Chalcanthite Group from the Gaiskoe Deposit,South Urals,Russia

Geology of Ore Deposits - Belogubite CuZn(SO4)2 ⋅ 10H2O, a new mineral of the chalcanthite group, is found in the Gai (Gaiskoe) massive sulfide deposit, South Urals, Russia. This mineral...     

Diffusion and mobility of electrically conducting defects in olivine

 Electrical conductivity of lherzolite (65% olivine), measured as a function of time after changes in the oxygen fugacity (f _o2) of the surrounding CO₂/CO atmosphere, is used to infer the diffusivity of the point defects responsible for conduction in olivine. A total of 63 equilibration runs at temperatures of 900, 1000, 1100, and 1200 ^∘C were fit using nonlinear parameter estimation to recover time constants (directly related to diffusivity) and conductivity steps. An observed f _o2 dependence in the time constants associated with re-equilibration implies two defect species of fixed diffusivity but with f _o2-dependent concentrations. Although the rate-limiting step may not necessarily be associated with a conducting defect, when time constants are converted to diffusivities, the magnitudes and activation energies agree extremely well with the model for magnesium vacancies (the slower species) and small polarons (holes localized on Fe³⁺) derived by Constable and Roberts (1997). This earlier study used an independent method of simultaneous modeling of thermopower and electrical conductivity as a function of f _o2 and temperature, on data from a different type of sample (a dunite). We observe that at high f _o2 where polarons dominate over magnesium vacancies in the defect population, re-equilibration is dominated by magnesium vacancy diffusion, and vice versa (at low f _o2 magnesium vacancies dominate and re-equilibration proceeds at the faster rate associated with polaron mobility). We interpret this to suggest association between the cation vacancies and polarons, as has been suggested by Tsai and Dieckmann (1997), making the concentration of the minority defect the rate-limiting step in the oxidation/reduction reactions. Received: 18 October 2000 / Accepted: 7 May 2002     

Mineralogical study of base metal tailings with various sulfide contents, oxidized in laboratory columns and field lysimeters

 Oxidation of a flotation-derived, low-sulfide tailings containing approximately 0.4 wt.% S was compared with simultaneously oxidized tailings containing 1.0 wt.% S and 2.5 wt.% S to assess their acid generating characteristics. Each tailings type was exposed to oxidation for three years in laboratory columns and in lysimeter pits in the field. In these tailings the sulfide mineral of principal concern with respect to acid generation is pyrrhotite (Fe _1-x S). In past studies the alteration of pyrrhotite has been characterized by initial replacement with marcasite (FeS₂) and ferric iron sulfates, which are followed by development of ferric oxyhydroxides such as goethite and lepidocrocite. Macroscopic characterization of the tailings shows varying and progressive degrees of oxidation correlative with the three different sulfur contents. As expected, the tailings with the lowest sulfur content are the least oxidized, and those with the highest sulfur content have reacted the most. The column tests, which represent accelerated reaction conditions relative to those for the lysimeter pits, show much higher degrees of oxidation, and a markedly more distinct boundary between the oxidized and unoxidized zones; as well, differences among the three tailings types are more pronounced. Received: 31 October 1997 · Accepted: 27 May 1997     

Assessment of natural attenuation of aromatic hydrocarbons in groundwater near a former manufactured-gas plant, South Carolina, USA

 Shallow, anaerobic groundwater near a former manufactured-gas plant (MGP) in Charleston, South Carolina, USA, contains mono- and polycyclic aromatic hydrocarbons (MAHs and PAHs, respectively). Between 1994 and 1997, a combination of field, laboratory, and numerical-flow and transport-model investigations were made to assess natural attenuation processes affecting MAH and PAH distributions. This assessment included determination of adsorption coefficients (K _ad ) and first-order biodegradation rate constants (K _bio ) using aquifer material from the MGP site and adjacent properties. Naphthalene adsorption (K _ad =1.35×10^–7 m³/mg) to aquifer sediments was higher than toluene adsorption (K _ad =9.34×10^–10 m³/mg), suggesting preferential toluene transport relative to naphthalene. However, toluene and benzene distributions measured in January 1994 were smaller than the naphthalene distribution. This scenario can be explained, in part, by the differences between biodegradation rates of the compounds. Aerobic first-order rate constants of ¹⁴C-toluene, ¹⁴C-benzene, and ¹⁴C-naphthalene degradation were similar (–0.84, –0.03, and 0.88 day^–1, respectively), but anaerobic rate constants were higher for toluene and benzene (–0.002 and –0.00014 day^–1, respectively) than for naphthalene (–0.000046 day^–1). Both areal and cross-sectional numerical simulations were used to test the hypothesis suggested by these rate differences that MAH compounds will be contained relative to PAHs. Predictive simulations indicated that the distributions of toluene and benzene reach steady-state conditions before groundwater flow lines discharge to an adjacent surface-water body, but do discharge low concentrations of naphthalene. Numerical predictions were "audited" by measuring concentrations of naphthalene, toluene, and benzene at the site in early 1997. Measured naphthalene and toluene concentrations were substantially reduced and the areal extent of contamination smaller than was both observed in January 1994 and predicted for 1997. Measured 1997 benzene concentrations and distribution were shown to be relatively unchanged from those measured in 1994, and similar to predictions for 1997. Received: 26 June 1997 · Accepted: 25 August 1997     

Potential application of oxygen-18 and deuterium in mining effluent and acid rock drainage studies

 Oxygen-18 (¹⁸O) and deuterium (D, or ²H) are routinely used in hydrologic, climatologic and geothermal studies. In hydrology, stable isotopes provide information on the type and topology (altitude and latitude) of the recharge waters and the historical effects on water, related to such physical processes as evaporation (in ponds), melting (of snow or ice), condensation, evapotranspiration and mixing. In geothermal studies, stable isotopes provide key information related to recharge and the various temperature-dependent water/rock isotope exchange reactions. The latter is assessed through the oxygen shift in the ¹⁸O/D correlation. At acid rock drainage (ARD) sites, water/rock interactions are primarily controlled by pH and oxidation potential. Using the isotopic characteristics of the rocks and the recharge waters as a basis, the relative oxygen shift of the ARD effluent can provide information on: (1) the residence time, (2) the rate of water/rock reactions, and (3) the actual pH at the rock/water interface. This paper offers a methodology for conducting oxygen and hydrogen isotope studies related to ARD and other mineral effluent problems. The methodology is based on: (1) comprehensive sampling of regional waters, ARD effluent and major contributing minerals and rocks, (2) isotopic and elemental analysis, and (3) data interpretation on the basis of a zero-dimensional (mass balance), multi-component mixing model. Received: 15 January 1999 · Accepted: 3 May 1999     

Listvenite-related gold deposits of the South Urals (Russia): A review

The Urals is a complex fold belt, which underwent long geological evolution. The formation of most gold deposits in the Urals is related to the collision stage. In this paper, we review some relatively small listvenite-related gold deposits, which are confined to the large Main Uralian fault zone and some smaller faults within the Magnitogorsk zone. The Mechnikovskoe, Altyn-Tash, and Ganeevskoe deposits are studied in detail in this contribution. They comprise the ore clusters along with other numerous small gold deposits, and constituted the sources for the gold placers exploited in historical time. The gold is hosted by metasomatites (listvenites, beresites) and quartz veins with economic gold grades (up to 20 g/t Au). Listvenites are developed after serpentinites and composed of quartz, fuchsite, and carbonates (magnesite, dolomite) ± albite. Volcanic and volcanoclastic rocks are altered to beresites, consisting of sericite, carbonates (dolomite, ankerite), quartz and albite. Pyrite and chalcopyrite are major ore minerals associated with gold; pyrrhotite, Ni sulfides, galena, sphalerite, arsenopyrite and Au-Ag tellurides are subordinate and rare. Gold in these deposits is mostly high-fineness (>900‰). The lower fineness (∼800‰) is typical of gold in assemblage with polymetallic sulfides and tellurides. The ores have been formed from the NaCl–CO₂–H₂O ± CH₄ fluids of low (∼2 wt% NaCl-equiv.) to moderate (8–16 wt% NaCl-equiv.) salinity at temperatures of 210–330 °C. The oxygen isotopic composition of quartz (δ¹⁸O) varies from 14.7 to 15.4‰ (Mechnikovskoe deposit), 13.2 to 13.6‰ (Altyn-Tash deposit) and 12.0 to 12.7‰ (Ganeevskoe deposit). The oxygen isotopic composition of albite from altered rocks of the Ganeevskoe deposit is 10.1‰. The calculated δ¹⁸O_H2O values of the fluid in equilibrium with quartz are in a range of 5.7–6.3, 4.2–4.6 and 6.3–6.7‰ respectively, and most likely indicate a magmatic fluid source.     

Environmental geochemistry of the Gulf Creek copper mine area, north-eastern New South Wales, Australia

 Past mining and smelting of sulphide ore (pyrite-chalcopyrite-sphalerite) at the abandoned Gulf Creek mine has resulted in a stream highly contaminated by acid mine drainage (pH: 2.2–3.4), as well as degradation of local soil and vegetation. Physical dispersion of secondary metal-bearing minerals from abandoned ore and waste dumps into Gulf Creek and adsorption and coprecipitation of dissolved metals and metalloids in the stream bed cause elevated Ag, As, Cd, Cu, Fe, Pb and Zn values in stream sediments. The bioavailability of individual heavy metals to freshwater organisms changes downstream, however, selective bioaccumulation processes in algae reject readily bioavailable Zn and concentrate less bioavailable Cu. Polluted soils in the vicinity of the mine and smelter sites are subject to continuing soil erosion and either support no vegetation, or a depauperate flora with certain species showing bioaccumulation of metals and resistance to high metal contents. Rehabilitation of disturbed areas should involve covering and sealing sulphidic mine waste or removal of ore and waste dumps, installation of a physical and chemical plant or construction of a wetland environment (plus anoxic lime drains), and import of topsoil and planting of local, metal-tolerant plant species. Received: 17 March 1998 / Accepted: 6 October 1998