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listelement.badge.dso-typeЭлемент, ON THE QUANTITATIVE EVALUATION OF THE NEUTRALIZING POTENTIAL OF HOST ROCKS(2007) Gas'kova O.L.; Bortnikova S.B.When sulfide ores are mined and processed and dump rocks and tailings are stored, one of the most important problems is the formation of acid drainage waters, which are produced during the oxidation of residual sulfides by atmospheric precipitates. The potential possibility of this process, which is usually referred to in the modern literature as acid mine drainage, is predetermined mostly by the composition and proportions of sulfides and gangue minerals that react with “water” in various geochemical environments. Our research was aimed at developing methodological approaches for the evaluation of the acid–base potential of rocks (i.e., the balance between their ability to produce and neutralize acids) on the basis of experimentally obtained data.listelement.badge.dso-typeЭлемент, ARCHEAN METATERRIGENOUS ROCKS: MAJOR GEOCHEMICAL CONSTRAINTS(2007) Maslov A.V.The paper summarizes data on the geochemistry of metaterrigenous rocks from 26 reference Archean territories: the Pilbara and Yilgarn blocks; Isua and Akilia complexes; Wittwatersrand, Swaziland, Pongola, and Yellowknife supergroups; Khapchanskaya and Gimol'skaya groups; Kan, Sharyzhalgai, Chupa, Slyudyanka, and Onot complexes; etc. The general sets of data points and the calculated median values of the concentrations of trace elements and their ratios are compared to those of Archean and post-Archean shales. In Ce/Cr-Co/Hf, Eu/Eu*-GdN/YbN, Ce/Cr-Th/Sc, Th/Sc-Sc, Th-La, La/Sm-Sc/Th, Yb-GdN/YbN, Th/Sc-Cr, Ni-Cr, and some other diagrams, the fields in which the most data points of Archean metaterrigenous rocks group are outlined. The results of this research indicate that there are no values of geochemical parameters that are inherent only in Archean or only in post-Archean fine-grained terrigenous rocks. Within 80-85% confidence levels, most individual compositions of Archean metaterrigenous rocks are characterized by the following geochemical parameters: (1) Th/Sc < 0.6-0.7, (2) Ce/Cr < 0.6, and (3) Eu/Eu*, > 0.70-0.75. If the median values are used, these ranges can be further constrained to (i) Th/Sc < 0.55, (ii) Ce/Cr < 0.4, (iii) Cr/Th > 25, and (iv) Th < 12 ppm. Compared to PAAS, Archean metaterrigenous rocks are characterized by higher median concentrations of Cr and Ni and the Eu/Eu*, Sc/Th, Cr/Th, and Co/Hf ratios, whereas the Nb, La, Ce, Yb, Hf, Th, and U concentrations and the La/Sm and Ce/Cr ratios of PAAS are, conversely, lower. The median values of the LaN/YbN ratios of reference Archean terranes can be either higher or lower than in PAAS, likely depending on the proportions of various rock types in the sources of the terrigenous material. The medians of the GdN/ YbN ratios of ~60% of the reference Archean metaterrigenous terranes in our databank are slightly higher than the GdN/YbN ratios of PAAS. The median values of the LaN/SmN ratios of Archean terrigenous rocks are mostly slightly lower than the typical PAAS ratios. © Pleiades Publishing, Ltd. 2007.listelement.badge.dso-typeЭлемент, HEAT CAPACITY OF SYNTHETIC HYDROUS MG-CORDIERITE AT LOW TEMPERATURES: THERMODYNAMIC PROPERTIES AND THE BEHAVIOR OF THE H2O MOLECULE IN SELECTED HYDROUS MICRO AND NANOPOROUS SILICATES(2007) Paukov I.E.; Kovalevskaya Y.A.; Rahmoun N.-S.; Geiger C.A.The heat capacity, Cp, of a synthetic hydrous cordierite of composition Mg1.97Al3.94Si5.06 O18 · 0.625H2O was measured for the first time using precise adiabatic calorimetry in the temperature range from 6 to 300 K. Hydrous Mg-cordierite was obtained by hydrothermal treatment of anhydrous Mg-cordierite (Paukov et al. 2006) at 4 kbar and 600 °C for 24 hours. The synthetic product was characterized using X-ray diffraction and powder IR spectroscopy. Rietveld refinement gives a = 17.060(2) Å, b = 9.721(1) Å, and c = 9.338(1) Å with V = 1548.7(3) Å3 and Δ = 0.25, and the IR spectrum shows only the presence of Class I-Type I H2O in the channel cavities. Small Cp anomalies were observed at 272.98 ±0.03 K and 239.43 ±0.13 K, which are thought to be related to very small amounts of H2O occurring in tiny fluid inclusions and to surface H2O, respectively. From the heat-capacity data on hydrous Mg-cordierite, various thermodynamic functions were calculated and are presented in table form. The calculated partial molar entropy for one mole of H2O in hydrous Mg-cordierite at 298.15 K and 1 bar is 80.5 J/(mol·K). The partial molar volume for H2O in hydrous Mg-cordierite at 298 K and 1 bar is zero. The Cp results, together with published heat-capacity data on three different zeolites, permit a comparison and analysis of their heat-capacity behavior. The heat-capacity behavior of H2O molecules in zeolites is more similar to that of ice at T < 300 K and not to gaseous H2O, which can be attributed to the presence of hydrogen-bonded H2O molecules. In contrast, the heat-capacity behavior for the "quasi-free" H2O molecule in cordierite is more similar to that of a free H2O molecule in the gaseous state between approximately 100 and 300 K. At T < 100 K, the energies of low-energy modes, especially external H2O translations, determine heat-capacity behavior. Model heat capacities for H2O in cordierite were calculated using the Einstein model and using as input data the results from inelastic neutron-scattering measurements on hydrous Mg-cordierite (Winkler and Hennion 1994). Reasonable agreement between experiment and calculations can be achieved using three H2O translational modes, one of which is hypothetical, and two librational H2O modes. The experimental spectra do not appear to show all six external H2O modes and further vibrational spectroscopic study is required to determine their energies. At T > 300 K, the heat capacity for H2O is the smallest in steam with values increasing in hydrous beryl and cordierite, to H2O in various zeolites, and finally to liquid H2O. This behavior may reflect the nature of the hydrogen bonding and the energies of internal H2O stretching modes, which decrease in energy with increasing hydrogen-bonding strength in the various systems.listelement.badge.dso-typeЭлемент, GEOCHEMISTRY AND STABLE ISOTOPIC SIGNATURES, INCLUDING CHLORINE AND BROMINE ISOTOPES, OF THE DEEP GROUNDWATERS OF THE SIBERIAN PLATFORM, RUSSIA(2007) Shouakar-Stash O.; Frape S.K.; Drimmie R.J.; Alexeev S.V.; Alexeeva L.P.The chemical composition and the isotopic characteristics of formation waters from the Siberian Platform are presented. The study involved samples of formation brines from depths ranging from 100 to ~4000 m at five different sites covering a large area of the Siberian Platform. Four water types were identified. The two main water types that were found are: (1) Ca-Cl brines that are believed to be the residual of an evaporated paleoseawater; and (2) Na-Cl brines that are derived mainly from halite dissolution. The origin of a third group of highly saline samples was not determined. However, the chemical and isotopic characteristics of this group of samples suggest that they were produced by various complex scenarios such as metamorphism, water-rock interaction, permafrost freezing and mixing. The last group of samples represents fresh and brackish waters across the area. A wide range for the natural variation of Br stable isotopes (between -0.80‰ and +3.35‰) was found. The δ81Br results obtained during this study indicate that Br stable isotopes can have large natural variations and that different evolutionary processes affecting water chemistry may cause significant fractionation. © 2006 Elsevier Ltd. All rights reserved.listelement.badge.dso-typeЭлемент, HYDROCARBONS AND OTHER VOLATILE COMPONENTS IN ALKALINE ROCKS FROM THE UKRAINIAN SHIELD AND KOLA PENINSULA(2007) Kryvdik S.G.; Kul'chitskaya A.A.; Voznyak D.K.; Kalinichenko A.M.; Zagnitko V.N.; Dubyna A.V.; Nivin V.A.Gas chromatography and other analytical techniques (EMR, PMR, and IR spectroscopy) were used to examine volatile components (CH4, C2-C3, CO2, CO, H2, H2O, and others) in alkaline rocks and minerals from the Ukrainian Shield (eight massifs and dikes of grorudites) and from the Khibina and Lovozero massifs in the Baltic Shield. The alkaline rocks from the Ukrainian Shield are mostly of Proterozoic (1.7-2.1 Ga) age. The alkaline rocks from the Kola Peninsula were confirmed to be rich in methane (21 ± 14 μ/g on average) and other hydrocarbons, whereas the analogous rocks from the Ukrainian Shield are poor in methane (2.1 ± 1.6 μ/g on average at a maximum of 14 μ/g). The latter rocks are richer in CO2, which is one of the major volatile components of alkaline rocks, including agpaitic nepheline syenites from the Kola Peninsula. The rocks from the Ukrainian Shield often have elevated contents of nitrogen (up to 20 μ/g). The reasons for the differences in the composition of volatile components of rocks from the Kola Peninsula and Ukrainian Shield are as follows: the agpaitic crystallization trends of large massifs in the Kola Peninsula and much less clearly pronounced agpaitic trends in the small massifs in the Ukrainian Shield, the affiliation of these rocks with different complexes, the deeper erosion levels of the Ukrainian alkaline massifs, different ages of these rocks, etc. © Pleiades Publishing, Ltd. 2007.