[en] Full text: Metamorphism in the Arunta Inlier is demonstrably polymetamorphic, and occurred during three main periods. The first period involved emplacement of granitic rocks and multiple episodes of high-grade metamorphism and occurred during the Palaeo- to Mesoproterozoic (∼1780 Ma to -1570 Ma: Strangways Orogeny, Chewings Orogeny). Metamorphism of this type is mostly of low-pressure/high-temperature facies (∼ 2.5 to 5 kbar). The second period of metamorphism occurred during the ∼300-400 Ma Alice Springs Orogeny, when thick-skinned, south-directed intraplate deformation thrust Arunta Inlier basement over the northern margin of the Amadeus Basin. In the Arunta Inlier basement this orogeny resulted in medium-pressure, greenschist to mid-amphibolite-facies metamorphism that re-worked Proterozoic assemblages, primarily in discrete shear zones.The third period of major metamorphism in the Arunta Inlier has only recently been identified on the basis of SHRIMP and Sm-Nd dating. It is also Palaeozoic in age and developed prior to the Alice Springs Orogeny in the interval ∼480-460 Ma (early to mid Ordovician). In the eastern Arunta Inlier (Harts Range Complex, Harts Range) pervasive medium- to high-pressure granulite-facies metamorphism (∼8-10 kbar, 800 deg C) occurred at this time in the Irindina Supracrustal Assemblage (Miller et al., 1997; Mawby et al., 1998; Hand et al., 1999). Peak metamorphism was associated with extensive fluid-absent partial melting of both metabasic and metapelitic lithologies, resulting in the formation of coarse-grained garnet-bearing assemblages. Peak metamorphism was followed by approximately 4 kbar of near-isothermal decompression to 6 kbar and 650-700 deg C, associated with the formation of a regional sub-horizontal foliation that is in places mylonitic. SHRIMP data suggests that the terrain was above the granite solidus (∼650 deg C) for 20-25 Ma implying that decompression was slow. The regional extent of the Ordovician metamorphism is currently poorly constrained. However, Scrimegeour et al. (1999) have suggested that mylonitic reworking of the Kanadra Granulite further NE may also be Ordovician in age. The granulite-facies metamorphism and high-T decompression was coeval with the development of the late Cambrian to early Ordovician marine Larapinta Group, which accumulated in a slowly subsiding sedimentary basin that appears to have had its depocenter along the axis of the now exhumed Arunta Inlier. The Brady Gneiss, which structurally overlies the Irindina Supracrustal Assemblage in the Harts Range Complex, underwent peak metamorphism at approximately 7 kbar and 700 deg C and followed a retrograde P-T path qualitatively similar to the Irindina Supracrustal Assemblage. It is suggested that metamorphism of the Irindina Supracrustal Assemblage and the Brady Gneiss should be referred to as the 'Larapinta Event' to highlight the synchroncity between the timing of high-grade metamorphism, and deposition of the Larapinta Group in the Amadeus Basin to the south of the Harts Range (authors)

[en] The Hill End Trough of central-western New South Wales was an elongate deep marine basin that existed in the Lachlan Fold Belt from the early Late Silurian to late Early Devonian. It is represented by a regionally extensive. unfossiliferous sequence of interbedded turbidites and hemipelagites of substantially silicic Volcanic derivation, which passes laterally into contemporaneous shallow-water sedimentary rocks. The Turondale and Merrions Formations of the Lower Devonian Crudine Group are two prominent volcanogenic formations in the predominantly sedimentary trough sequence. They contain a range of primary and resedimented volcanic facies suitable for U-Pb dating. These include widespread subaqueous silicic lavas and/or lava cryptodomes. and thick sequences of crystal-rich volcaniclastic sandstone emplaced by a succession of muss-flows that were generated by interaction between contemporaneous subaerial pyroclastic flows and the sea. Ion microprobe dating of the two volcanogenic formations by means of the commonly used SL 13 zircon standard yields ages ranging between 411.3 ± 5.1 and 404.8 ± 4.8 Ma. Normalising the data against a different zircon standard (QGNG) yields preferred slightly older mean ages that range between 413.4 ± 6.6 and 407.1 ± 6.9 Ma. These ages broadly approximate the Early Devonian age that has been historically associated with the Crudine Group. However, the biostratigraphically inferred late Lochkovian - early Emsian (mid-Early Devonian) age for the Merrions Formation is inconsistent with the current Australian Phunerozoic Timescale, which assigns an age of 410 Ma to the Silurian-Devonian boundary, and ages of 404.5 Ma and 395.5 Ma to the base and top of the Pragian, respectively. There is, however, good agreement if the new ages are compared with the most recently published revision of the Devonian time-scale. This suggests that the Early Devonian stage boundaries of the Australian Phanerozoic Timescale need to be revised downward. The new ages for the Merrions Formation could also provide a time point on this time-scale for the Pragian to early Emsian, for which no data are presently available. Copyright (1999) Geological Society of Australia

[en] Mamyu rock specimens, were collected from the sor-rondane mountains and Breid Bay area of Drojnning Maud land, eastern Antarctica, during the 2nd Pakistan Antarctic Expedition, 1992-93. Petrography and geochemical studies suggest that the rocks are essentially of igneous origin. The samples dredged from ocean bottom include olivine basalt, amygdaloidal volcanics, dacites and rhyodacites. A majority of these rocks are calc-alkaline and formed by the fraction of olivine, clinopyroxene and plagioclase +- titanomagnetite. Most of these rocks apparently formed in an island arc or continental margin set up. However, volcanics showing ocean floor basalt character are also present. A metamorphosed and deformed basement consisting of amphibolites, calc-silicate rocks and gneisses is intrude by under formed or only slightly deformed granites with a minor arkosic sandstone cover. The granites are chemically distinguished as I-type, originate at deeper crystal level by collisional/subduction related processes during organic environments. (author)

[en] Groundwater recharge processes were investigated in central Nevada by examining the relationships between the stable isotope (δD and δ¹⁸O) compositions of snowfall, snowmelt, alpine spring waters, and regional groundwaters. Snowmelt infiltration is inferred to be the dominant source of groundwater recharge in this region. Bulk snow cores collected throughout central Nevada near the time of maximum accumulation have δD-δ¹⁸O pairs that plot subparallel to the global meteoric water line (GMWL), but are shifted to the right of the line, implying kinetic isotope enrichments. Heavy isotope enrichments occur at the base of snowpacks due to fractionation during snow metamorphism, sometimes resulting in remarkably systematic isotopic variations. Ice crystals in the soil immediately beneath the snowpack can be strongly depleted in heavy isotopes relative to the overlying snow, implying fractionation or exchange with the snowpack. Late season ablation processes tend to homogenize isotopic variations between snowpack layers, and cause the bulk isotopic composition of the snowpack to become enriched in ¹⁸O by 2-3 per mille relative to the composition during peak accumulation. The dynamic evolution of the snowpack and snowmelt isotopic compositions over time makes it difficult to directly ascertain groundwater recharge compositions without careful mass balance measurements. Preliminary evidence suggests that small local springs may be reasonable indicators of the integrated isotopic value of the snowmelt recharge in a particular area. Springs and snowmelt runoff samples collected throughout central Nevada during the peak runoff plot along a least squares regression line with the equation δD = 7.3δ¹⁸O - 7, which is similar to the line obtained for 28 metamorphosed snow cores collected during peak accumulation (δD = 7.5δ¹⁸O - 3). These results suggest that kinetic fractionation processes during snow metamorphism and ablation may largely account for the heavy isotope enrichments that are widely observed in groundwaters from both local and regional flow systems in Nevada. (author)

[en] At Schluesselgrund valley, East Germany an uranium mine dump of about 4 Mil m³ had been built due to an intensive exploitation of uranium ore deposit near Dresden. In order to evaluate and to specify the current and future environmental impact of the disposal site, investigations of environ-mental and radioactive isotopes have been performed as part of a hydrogeological and hydrochemical study at the Schluesselgrund Mine Dump. Beneath the dump we find significantly contaminated water in the first and second aquifer in a narrow strip of faulted rock. The main contaminants comprise of uranium and radium as well as of zinc, nickel and sulphate. The mean residence time of those waters percolating the dump is about 1 to 5 years with contributions of an older component. The ³H and ⁸⁵Kr contents in the groundwater of the first aquifer yield a mean residence time of about 20 years, which obviously is less than the life time of the dump (built in 1967). The second aquifer shows a ground-water mixing system. Within this study, the groundwater of the third aquifer with ³H contents close to or below detection limit did not show any detectable influence of the dump waters. This is supported by high groundwater ages of several thousand years according to the ¹⁴C values. Close to the former mine system, there are local groundwater samples from the third aquifer showing ³H contents of up to 8 TU, which may be caused by groundwater flowing on fractures and on pathways within the former mine system. Part of the dump waters drain into the nearby rivers by interflow processes as indicated by stable isotopes. (author)

[en] The isotopic compositions of oxygen and hydrogen of the shallow groundwater in the Gurinai Grasslands west of the Badajilin Desert in China are unusual: Both the δ¹⁸O and δ²H values fit an apparent local meteoric water line with an unusually low deuterium excess of <-20 per mille. Four possible causes have been considered: (a) an admixture of fossil lake water, (b) an admixture of water from the Black River, (c) unusual isotopic compositions of the regional precipitation, and (d) processes which secondarily modify the isotope signature. Cases (a) and (b) have been excluded on the basis of our former isotope results. In two other case studies in Chile and Canada similar unusual isotope compositions were found for shallow groundwater in the Valle del Rio Copiapo in the arid part of central Chile and for water in lakes located along the northern tree line of Canada, respectively. The extremely low deuterium excess can be explained with the physical processes occurring in the unsaturated zone which modify the isotopic compositions of the pore water in arid regions. The slope of the evaporation lines in the δ¹⁸O/δ²H plot decrease from 4 to 5 for open water systems down to about 2.0 in the unsaturated zone with increasing thickness of the dry cover sediment. In the Gurinai Grasslands and at the foot of the megadunes in the Badajilin Desert the dry cover sediments are 0.5 to 3.5 m thick, both the water level and the isotope enrichment due to evaporation are constant over the year. There is a linear interrelationship between δ¹⁸O values and the depth of the water table, Assuming varying slopes of the evaporation lines, a similar grain size composition of the cover sediments throughout the study area, steady-state conditions of the isotope profiles in the un-saturated zone before succeeding recharge events and groundwater recharge lower than the amount of pore water in the unsaturated zone the described phenomenon is explainable. It is also reflected from the observed isotopic results of the described case studies in Chile and Canada. It may be applicable to estimate regional evaporation rates and recharge rates for groundwater balance studies. (author)

[en] Method of environmental isotopes is used on problems related to the origin of water systems. The local precipitations and Prespa lakes water were examined as a potential sources of recharge to Dry Mountain groundwater. The mean elevation of infiltration area (groundwater recharge area) were expected to be higher than Prespa lake elevation. The altitude effect of the isotopic composition of the meteoric water is used for the identification of waters coming from different potential groundwater recharge sources of Dry Mountain

[en] Surface waters are primary receiver for wastes discharged in liquid form. Continuous expansion of industrial activities and urban agglomerations results in still increasing amount of pollutants discharged into rivers, lakes and coastal sea areas. This results in harmful effects on environment equilibrium in natural water reservoirs affected with discharged pollutants leading in extreme cases, to complete disappearance of biological life in water regions highly loaded with pollutants. On the other hand, the surface waters constitute one of most important water sources for municipal and industrial use. High degree of their pollution, beside of technical difficulties associated with treatment of water in order to make it suitable for both household and process purposes, creates numerous hazards of secondary nature through various kinds of potable water, fish and industrial water contamination. The proper understanding the effluent transport process mechanism and influence of hydrological and morphological conditions on it will approach us to more precise assessment of ecological hazards. All previous experience have based on the solutions of dispersion equation for straight cannel approximation. Such solution do not take into account the river bed morphology which suspected to play a significant role for pollution transport in unregulated rivers. There are a few publications in which the authors introduce the factors depending on river morphology to the model equation, such approach complicate very much the analytical solutions of model equations even for single dimension. One of more promising approaches seems to be the dead volume model. The dead volumes are generated by river bed irregularities. Validation of such approach can be checked in natural conditions. That was the main topic of our work in 1998. We carried out a series of field experiments at the river being carefully selected from the view point of experimental conditions. The 5 km section of Wkra River have been selected after hydrological analysis. Wkra River is a small unregulated right tributary of Vistula River (average depth 1.5 m and width 30 m). The five measuring cross section was localized practically in every 1 km of river course

[en] The investigation of the origin and dynamics of groundwater in the vicinity of dams and reservoirs is a major concern of the responsible authorities in case of important leakage problems. In most cases, local groundwater and water related tot he leakage emerge downstream of the dam with a complex mixing pattern. The proper characterization of the flow rate and flow patterns of water derived from the reservoir requires the use of several hydrological techniques, including environmental isotopes and artificial tracers. Among the common isotope tools, oxygen-18 deuterium and tritium are routinely used. The different origin of surface waters stored in the reservoir, and local groundwaters, usually derived from local recharge, result in distinct isotope signatures, allowing a proper characterization of each water type. However, practical work in investigating this type of problems under different geographic and climatic conditions has shown that in many cases, hydrochemistry and these isotopes do not provide a convincing and complete evidence about the origin and mixing patterns of the two types of waters. The proximity of the recharge areas and the short transit time of local groundwater do not result in significant differences in the chemical and/or isotope contents. ¹³C/¹²C ratios in the Total Dissolved Inorganic Carbon (TDIC) has been successfully used to investigate some aspects of leakage problems in several dams located in temperate and tropical climates

[en] Duitama city (100.000 inhabitants) lies in a plateau of the Colombian Andean Range. Fifty per cent of water supply is abstracted from the main aquifer and accounts for more than 80% during dry seasons. As far as piezometric level is declining progressively, it is suspected that ground water abstration is greater than natural replenishment and any increment in production wells and ground water abstraction may damage ground water sources for sustainable development and management. The main aquifer of the area is a Quaternary alluvial deposit consisting of sand, gravels and conglomerates, with a thickness up to 180 m, and overlain clay deposits, with have a thickness from 20 to 60 m, in most part of the aquifer. On the west and middle part of the plain, the Quaternary lies on Cretaceous sandstone, claystone and limestone formations: towards east, on Palaeozoic claystone and sandstone formations. A hydrogeological study was carried out by means of conventional and isotopes techniques, in order to identify ground water origin and particularly to investigate present infiltration and recharge