No abstract available

[en] Essential to the use of stable isotopes as natural tracers and geothermometers is the knowledge of equilibrium isotope partitioning between different phases and species, which is usually a function of temperature only. The one exception known to date is oxygen and hydrogen isotope fractionation between liquid water and other phases (steam, gases, minerals), which changes upon the addition of salts to water, i.e., the isotope salt salt effect. Our knowledge of this effect, the difference between activity and composition (a-X) of isotopic water molecules in salt solutions, is very limited and controversial, especially at elevated temperatures. For the last several years, we have been conducting a detailed, systematic experimental study at Oak Ridge National Laboratory to determine the isotope salt effects from room temperature to elevated temperatures (currently to 500 degree C). From this effort, a simple, coherent picture of the isotope salt effect is emerging, that differs markedly from the complex results reported in the literature. In this communication, we present an overview on the isotope salt effect, obtained chiefly from our study. Observed isotope salt effects in salt solutions are significant even at elevated temperatures. The importance and implications of the isotope salt effect for isotopic studies of brine-dominated systems are also discussed in general terms

[en] Several geological evidences support the occurrence of volcanic conduit enlargement during explosive events (e.g. presence of lithic fragments in most pyroclastic deposits), with significant effects on the eruptive dynamics, particularly on the mass discharge rate. Conduit wall collapse is supposed to be a relevant enlargement process, being more intense near and above the fragmentation level. Nonetheless, the influence of country rock conditions has never been addressed, and its implications on the eruptive dynamics are still unclear. This work focuses on the effects of the country rock mechanical parameters and the presence of unconfined aquifers on conduit stability, using a 1D steady-state model and the application of two collapse criteria. For given magma properties and conduit dimensions, it emerges that conduit stability is mainly controlled by the friction angle of the country rocks and, to a lesser extent, by the cohesion. The horizontal stress gradients are only significant when the Mohr-Coulomb criterion is employed, whereas the variability in the vertical stress gradient has a minor effect on conduit stability. Moreover, the presence of unconfined aquifers is an important destabilizing factor, which is consistent with the ejection of significant amounts of lithic fragments in many phreatomagmatic eruptions.

[en] Time-series fractal dimensions of fluid conditions and their particular components have been calculated. It has been shown that the components of different genetic origins had different values of fractal dimension. It proves that fractal analysis opens up new opportunities in fluid condition studies. (author)

[en] Full text: Geothermal waters have been used on a large scale for bathing, drinking and medical purposes. These waters often have a very high mineral content because solubility increases with temperature. Ground waters are in close contact with soil and rocks containing radium. Once formed by decay from radium, radon gas may diffuse through rocks pores and geological discontinuities and may dissolve in these waters. Radon and other natural radionuclides are transported to the surface where radon can easily diffuse into the atmosphere. Then it may be possible to find out significant radon levels at places like geothermal spas. In this work the most important natural radionuclide activity concentrations in different thermal spas of Argentina were measured to characterize waters and to evaluate the exposure of workers and members of the public. Three passive methods were used to measure radon in air. One of them is an screening method based on the radon adsorption on activated charcoal. The other two methods are time integrated ones, Cr-39 or Makrofol tracks detectors, which can be exposed between two and three months. To characterize waters other natural radionuclides have been also measured. Uranium concentration was measured by fluorimetry. Ra-226 and Pb-210 measurements were performed by radiochemical methods and liquid scintillation. The results obtained were compared with the guidelines values recommended by WHO and EPA for drinking waters and, in the case of radon in air, the results were compared with values established by BSS-115. In order to assess worker doses, the higher value measured for radon in air and real scenario data were taken into account. Moreover, in situ dose rate measurements were also performed and then compared with natural background values. In relation with water characterization, almost all values obtained for the geothermal waters analyzed were below the corresponding guidance levels. Taking into account the highest value measured of radon in air, the maximum annual effective doses calculated resulted below the corresponding dose criteria for members of the public and in the order of it for workers. As values measured may be variable, it is suggested that the Thermal Spas be re-evaluated to determine its evolution over time. (author)

[en] Chemical and isotopic (δ¹⁸O, δD) data of fluids from the Los Humeros geothermal field wells collected before exploitation, were used to obtain the total discharge and the reservoir liquid phase compositions to obtain reference values which are useful to investigate reservoir processes during exploitation. Gas equilibria (FT-HSH2 method), was used to estimate both, the reservoir temperature and the reservoir excess steam. The reservoir temperature ranged from 280 deg C for the upper liquid-dominated reservoir to 330 deg. C for the deeper, low- liquid saturation reservoir. Excess steam values were lower for the upper reservoir while for deeper, mostly steam wells (H-23 and H-18) such values were almost 100%. Reservoir data interpretation indicated that a multi-steam separation process with condensate counter-flows occurs in the Colapso Central zone, this process is schematically shown in Fig. 1 where the elevation of production zone vs δ¹⁸ O values were plotted. This process explains the wide range of isotopic composition of the fluids, which was found to be from -1.2 (well H-18) to -6.7 (well H-16R) for δ¹⁸O; and from -52.2 (well H-18) to -80.4 (well H-16R) for δD. The multi-separated steam is produced by wells H-10 at an elevation of 742 m. a. s. l.; H-16 at an elevation of 790 m. a. s. l. and subsequently by the well H-16R (H-16 after repaired) at an elevation of 1400 m. a. s. l. The convective process transports non-volatile specia to the shallower levels of the reservoir where higher CO₂ concentrations in the reservoir liquid were obtained. The convective process can be the responsible for the HCl presence in well H-16 as well as in other wells in the Colapso Central zone. Exploitation of the upper reservoir in the Colapso Central, has caused the ascent of hotter fluids through fractures and a heating process for this zone was also inferred

[en] Short communication

[en] Short communication

[en] According to scientific research and technical summing up reports, based on the field investigation, the possible problems of terrestrial heat and moderate-hot water during the exploitation of an uranium deposit in Jiangxi Province are discussed. The preliminary analysis and discussion on the distribution, distribution regularity, causes of formation and correlation of terrestrial heat and moderate-hot water at the uranium deposit are carried out

[en] In the article problems of brine tubing bending and bent string cutting methods in the well conditions has been described. Implementation of safety joint in the brine string as an alternative solution that eliminates the need of cutting has been presented as well. (authors)