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1.
Robert Elihu Stauffer 《Geochimica et cosmochimica acta》1982,46(3):465-474
Potential solubility controls on phosphorus in Yellowstone National Park geothermal waters were investigated using the analytical phosphate estimates of Stauffer and Thompson (1978), the computer program, WATEQF, and adopting the equilibrium constant: for fluorapatite (FAP = Ca5(PO4)3F) dissolution. The near-boiling high-Cl geyser and spring effluents are at or near saturation with respect to (with) FAP. The sixteen representative springs in this category had FAP saturation indices () ranging from ? 3.2 to +4.9 and averaging +0.9. The strongly positive indices were all associated with the highly alkaline conditions resulting from adiabatic cooling in the near surface environment. Hot spring waters indicating extensive dilution (reduced Cl) by meteoric water have lower pH's, and despite PO4 and Ca concentrations an order of magnitude higher than the geysers, are still frequently undersaturated with FAP. The travertine-depositing “Mixed-water” springs are invariably supersaturated with FAP at ground surface and at or near saturation with hydroxylapatite. Supersaturation may result from kinetic inhibition of apatite crystallization by the elevated Mg2+, HCO3?, and lower temperatures in these springs. The phosphates may be residuals of the meteoric dilution water.Separately, if Strübel's temperature-dependent estimates of fluorite (CaF2) solubility are adopted, the high-Cl geysers and springs on “Geyser Hill” and at Norris are consistently undersaturated with CaF2 at the 90–100° orifice temperatures. The apparent disequilibrium may reflect fluorite equilibration at the much higher temperatures (> 200°C) in the deeper enthalpy reservoirs. 相似文献
2.
Experimentally reversed quartz solubilities at 250°C and at 250, 500 and 1000 bars yield values of the logarithm of the molality of aqueous silica of ?2.126, ?2.087 and ?2.038, respectively. Extrapolation of quartz solubility to the saturation pressure of water at 250°C results in a log molality of aqueous silica of-2.168. These solubility determinations and analyses of fluid pressures in geothermal systems indicate that pressure is significant when calculating quartz equilibrium temperatures from silica concentrations in waters of deep thermal reservoirs.The results of this investigation, combined with other reported quartz solubility measurements, yielded a pressure-sensitive “silica geothermometer” for fluids that have undergone adiabatic steam loss of where P is the fluid pressure in bars and mSi(OH)4 · 2H2O represents the molality of aqueous silica measured in surface samples. The geothermometer is applicable to solutions in equilibrium with quartz from 180°C to 340°C and fluid pressures from H2O saturation to 500 bars. 相似文献
3.
Dimitri A Sverjensky 《Geochimica et cosmochimica acta》1984,48(5):1127-1134
A linear correlation exists between the standard Gibbs free energies of formation of calcite-type carbonates (MCO3) and the corresponding conventional standard Gibbs free energies of formation of the aqueous divalent cations (M2+) at 25 °C and 1 bar ΔGMCO30 = m(ΔGf,M2+0) ? 141,200 cal · mole?1 where m is equal to 0.9715. This relationship enables prediction of the standard free energies of formation of numerous hypothetical carbonates with the calcite structure. Associated uncertainties typically range from about ± 250 to 600 cal · mole?1. An important consequence of the above correlation is that the thermodynamic equilibrium constant for the distribution of two trace elements M and N between carbonate mineral and aqueous solution at 25 °C and 1 bar is proportional to the free energy difference between the corresponding two aqueous ions: In Combination of predicted standard free energies, entropies and volumes of carbonate minerals at 25°C and 1 bar with standard free energies of aqueous ions and the equation of state in Helgesonet al. (1981) enables prediction of the thermodynamic equilibrium constant for trace element distribution between carbonates and aqueous solutions at elevated temperatures and pressures. Interpretation of the thermodynamic equilibrium constant in terms of concentration ratios in the aqueous phase is considerably simplified if pairs of divalent trace elements are considered that have very similar ionic radii (e.g., , ). In combination with data for the stabilities of complex ions in aqueous solutions, the above calculations enable useful limits to be placed on the concentrations of trace elements in hydrothermal solutions. 相似文献
4.
Stable carbon isotope fractionation by seventeen species of marine phytoplankton, representing the classes of Bacillariophyceae, Chlorophyceae, Prasinophyceae, Chrysophyceae, Haptophyceae and Dinophyceae have been determined in laboratory culture experiments using bicarbonate enriched artificial sea water. The values (ΔHCO3? = δ13C of algae vs HCO3?) range from ?22.1 to ?35.5%. Nitzschia closterium shows the smallest fractionation of ? 22.1% and Isochrysis galbana, the greatest of ?35.5%,. Since these algae were cultured under identical laboratory conditions, the wide range of ΔHCO3? values is seemingly due to the presence of different metabolic pathways within these organisms.A temperature dependent fractionation of 0.36% per °C with decreasing temperatures was measured for Skeletonema costatum whereas, smaller temperature dependencies of ?0.13, +0.15 and ?0.07%. per °C were observed for Dunaliella sp., Monochrysis lutheri and Glenodinium foliaceum, respectively.The consistency of values of Skeletonema costatum, Dunaliella sp. and Monochrysis lutheri grown at salinities of 22, 26, 32 and 36% indicates that natural salinity variations have negligible effects on the isotopic composition of marine phytoplankton. 相似文献
5.
Variations in the chemical composition of sedimentary rocks and the nature of kerogen through geologic time were investigated in order to obtain information on biological and environmental evolution during the pre-Phanerozoic eon. Rock samples differing in lithology, depositional environment, and age were pulverized, pre-extracted with organic solvents, and analyzed for total nitrogen (N), phosphorus (P) and organic carbon (org. C or CT). Variations in the molecular structure of kerogen were measured by determining the ratio of org. C content after pyrolysis (CR) to org. C content before pyrolysis (CT), the ratio being considered an index of the degree of condensed-aromatic (as opposed to aliphatic) character. The rocks included mudstones (Early Archean (> 3 · 109 years old) to Miocene), carbonate rocks (mid-Proterozoic (1.3 · 109 years old) to Eocene), cherts (Early Archean (> 3 · 109 years old) to Late Proterozoic (0.8 · 109 years old)), and coal (Archean (> 2.7 · 109 years old) to Early Proterozoic (～1.8 · 109 years old)).The mudstones and carbonates showed progressive increase in org. C content with decreasing age, as reported by other investigators, but the cherts unexpectedly showed a decrease in org. C content with decreasing age. In all samples, a simple inverse correlation between ratio and org. C was observed, each rock type forming its own trend separate from but parallel to those of the other rock types. Thus, the older cherts tend to be richer in org. C and have lower ratios, but the older carbonates and mudstones are poorer in org. C and have higher ratios. For a given org. C concentration, chert has the highest ratio and carbonate rock the lowest, mudstone being intermediate; this may mean that chert is relatively ineffective as a catalyst for the thermal cracking of kerogen or that it inhibits cracking. N appears to be correlated with org. C. The relationship between ratio and org. C or N suggests that the concentrations of org. C and N in sedimentary rocks are largely determined by selective elimination of labile aliphatic and nitrogenous groups of kerogen during post-depositional maturation, although the nature, abundance and depositional environment of the organic source material must be taken into consideration as well. The observed secular variations of org. C, N and ratio may be ascribed to several possible causes, including age-dependent post-depositional alteration of kerogen, secular decrease in the ratio of the atmosphere and hydrosphere during pre-Phanerozoic time, secular increase in rates of accumulation of organic matter in sediments and evolutionary changes in the composition of the biological source material. The secular variations of the carbonates and mudstones could be accounted for by age-dependent cumulative effects of post-depositional alteration alone, whereas the secular variations of the cherts probably reflect changes in the nature of the biological source material and the composition of the atmosphere and hydrosphere. The available evidence suggests that primary characteristics of kerogen are better preserved in chert than in the other types of sediment.The ratios of the carbonates and cherts correlate negatively with the absorbance ratios of “humic matter” extracted from the same rock samples with benzene—methanol. Thus, the greater the degree of condensed-aromatic character of the kerogen, the greater the degree of condensed-aromatic character of the solvent-extractable bituminous “humic matter” with which it is associated. In addition, the ratio of aliphatic to carbonyl-type groups () in the extractable “humic matter” of carbonates and cherts correlates with the non-extractable org. C content of the rocks, suggesting that the org. C data are related to the degree of aliphatic character of the kerogen. The chemical similarity between extractable “humic matter” and its associated kerogen is evidence that the “humic matter” is as old as its rock matrix and can be accepted as a valid chemical fossil. It also suggests that information obtainable from kerogen may be gotten more easily, rapidly and cheaply from solvent-extractable organic matter. The mudstones showed little or no relationship between ratio and ratio, or between ratio and org. C content. The data are consistent with the hypothesis that the kerogen in the carbonates and cherts is autochthonous, whereas the kerogen in the mudstones is partly allochthonous, implying the existence of soil humus and soil organisms in pre-Phanerozoic times. Moreover, the existence of coal in Archean sediments is consistent with the existence of very shallow-water and possibly terrestrial microfloras possessing adaptations for protection against ultraviolet solar radiation.The P content of the sediments showed a complicated zig-zag pattern of variation through geologic time. All the different suites of samples gave similar results, indicating that the variations represent phenomena whose effects were worldwide and independent of local environment. P levels are low in the early pre-Phanerozoic but rise with decreasing age until ～ 1 · 109 years B.P., then fall to a minimum at (～0.7–0.8) · 109 years B.P., and rise again to a lower Paleozoic (Ediacarian?) maximum, decline to a later Paleozoic minimum, and then rise again. The low P content of early pre-Phanerozoic sediments could be due to several factors, including high CO2 content of seawater, anaerobic conditions in the sea, absence of stable-shelf environments, and low rates of primary production. The minimum in the Late Proterozoic is tentatively attributed to the Late Proterozoic glaciations. The data are consistent with the theory that the glacial episode was of worldwide extent. 相似文献
6.
Thermodynamic calculations for selected silicate-oxide-fluorite assemblages indicate that several commonly occurring fluorite-bearing assemblages are restricted to relatively narrow fields at constant P?T. The presence of fayalite-ferrohedenbergite-fluorite-quartz ± magnetite and ferrosalite-fluorite-quartz-magnetite assemblages in orthogneisses from Au Sable Forks, Wanakena and Lake Pleasant, New York, buffered fluorine and oxygen fugacities during the granulite facies metamorphism in the Adirondack Highlands. These buffering assemblages restrict to 10?29 ± 1 bar and to 10?16 ± 1 bar at the estimated metamorphic temperature of 1000K and pressure of 7 kbar. The assemblage biotite-magnetite-ilmenite-K-feldspar, found in the same Au Sable Forks outcrop as the fayalite-fluorite-ferrohedenbergite-quartz-magnetitie assemblage, restricts H2O fugacities to less than 103·3 bar. These fugacities limit H2 and HF fugacities to less than 101 bar for the Au Sable outcrop. The data indicate that relative to H2O, O2, H2, F2 and HF are not major species in the fluid equilibrated with Adirondack orthogneisses. The calculated F2 fugacilies are similar to the upper limits possible for plagioclase-bearing rocks and probably represent the upper limit for metamorphism in the Adirondacks and in other granulite facies terranes. 相似文献
7.
Walter Riesen Heinz Gamsjäger Paul W. Schindler 《Geochimica et cosmochimica acta》1977,41(9):1193-1200
The carbonato and hydrogencarbonato complexes of Mg2+ were investigated at 25 and 50° in solutions of the constant ClO4? molality (3 M) consisting preponderantly of NaClO4. The experimental data could be explained assuming the following equilibria: Mg2+ + CO2B + H2O ag MgHCO+3 + H+, , Mg2+ + 2 CO2g + 2 H2Oag Mg(HCO3)02 ± 2 H+, , ?15.37 ± 0.39 (50°), Mg2+ + CO2g + H2Oag MgCO03 + 2 H+, ,?15.23 ± 0.02 (50°), with the assumption γMgCO30 = γMg(HCO3)02, ΔG0(I = 0) for the reaction MgCO03 + CO2g + H2O = Mg(HCO3)02 was estimated to be ?3.91 ± 0.86 and 0.6 ± 2.4 kJ/mol at 25 and 50°C, respectively. The abundance of carbonate linked Mg(II) species in fresh water systems is discussed. 相似文献
8.
Darrell Kirk Nordstrom 《Geochimica et cosmochimica acta》1982,46(4):681-692
While gibbsite and kaolinite solubilities usually regulate aluminum concentrations in natural waters, the presence of sulfate can dramatically alter these solubilities under acidic conditions, where other, less soluble minerals can control the aqueous geochemistry of aluminum. The likely candidates include alunogen, Al2(SO4)3 · 17H2O, alunite, KAl3(SO4)2(OH)6, jurbanite, Al(SO4)(OH) · 5H2O, and basaluminite, Al4(SO4)(OH)10 · 5H2O. An examination of literature values shows that the log for alunite and log for basaluminite. In this report the log is estimated for alunogen and log is estimated for jurbanite. The solubility and stability relations among these four minerals and gibbsite are plotted as a function of pH and sulfate activity at 298 K. Alunogen is stable only at pH values too low for any natural waters (<0) and probably only forms as efflorescences from capillary films. Jurbanite is stable from up to the range of 3–5 depending on sulfate activity. Alunite is stable at higher pH values than jurbanite, up to 4–7 depending on sulfate activity. Above these pH limits gibbsite is the most stable phase. Basaluminite, although kinetically favored to precipitate, is metastable for all values of pH and sulfate activity. These equilibrium calculations predict that both sulfate and aluminum can be immobilized in acid waters by the precipitation of aluminum hydroxysulfate minerals.Considerable evidence supports the conclusion that the formation of insoluble aluminum hydroxy-sulfate minerals may be the cause of sulfate retention in soils and sediments, as suggested by Adams and Rawajfih (1977), instead of adsorption. 相似文献
9.
Tomáš Pačes 《Geochimica et cosmochimica acta》1975,39(4):541-544
If the temperature of ground water is below 75°C and the partial pressure of CO2 in the aquifer is above 10?4 atm, a chemical steady-state between water and felsic rocks (rather than chemical equilibrium) may be maintained. The temperature of water in the aquifer may be estimated using a modified form of the Na-K-Ca geothermometer from, . where the departure of the steady-state from equilibrium, , is a function of : . 相似文献
10.
Manfred Schidlowski Peter W.U Appel Rudolf Eichmann Christian E Junge 《Geochimica et cosmochimica acta》1979,43(2):189-199
One hundred and twenty-four carbonate samples from the meta-sedimentary sequence of the 3.7 × 109 yr old Isua supracrustal belt (W-Greenland) have yielded a δ13Ccarb average of ?2.5 ± 1.7%. vs PDB and a δ18Ocarb average of +13.0 ± 2.5%. vs SMOW. The oxygen mean comes fairly close to the averages of other early Precambrian carbonates. The carbon average, however, is some 2%. more negative than those of younger marine carbonates. In terms of a simple terrestrial 13C mass balance, if δ13Ccarb values are original sedimentary values, this more negative δ13C average would imply a considerably smaller ratio in the sedimentary shell during Isua times, and would thus support the concept of a gradual buildup of a sedimentary reservoir of organic carbon during the early history of the Earth. Since, however, the Isua supracrustal rocks have experienced amphibolite-grade metamorphism, which in other areas has been shown to lower δ13Ccarb values, it is most likely that the original values of these rocks were approx 0%.. This indicates that Corx and Ccarb were present in the ancient carbon reservoir in about ‘modern’ proportions. Unless this early stabilization of the terrestrial carbon cycle in terms of a constant partitioning of carbon between the reduced and oxidized species is shown to have been caused by some inorganic geochemical process, a considerably earlier start of chemical evolution and spontaneous generation of life must be considered than is presently accepted. 相似文献
11.
Significant amounts of SO42?, Na+, and OH? are incorporated in marine biogenic calcites. Biogenic high Mg-calcites average about 1 mole percent SO42?. Aragonites and most biogenic low Mg-calcites contain significant amounts of Na+, but very low concentrations of SO42?. The SO42? content of non-biogenic calcites and aragonites investigated was below 100 ppm. The presence of Na+ and SO42? increases the unit cell size of calcites. The solid-solutions show a solubility minimum at about 0.5 mole percent SO42? beyond which the solubility rapidly increases. The solubility product of calcites containing 3 mole percent SO42? is the same as that of aragonite. Na+ appears to have very little effect on the solubility product of calcites. The amounts of Na+ and SO42? incorporated in calcites vary as a function of the rate of crystal growth. The variation of the distribution coefficient () of SO42? in calcite at 25.0°C and 0.50 molal NaCl is described by the equation where and are constants equal to and , respectively, and is the rate of crystal growth of calcite in mg·min?1·g?1 of seed. The data on Na+ are consistent with the hypothesis that a significant amount of Na+ occupies interstitial positions in the calcite structure. The distribution of Na+ follows a Freundlich isotherm and not the Berthelot-Nernst distribution law. The numerical value of the Na+ distribution coefficient in calcite is probably dependent on the number of defects in the calcite structure. The Na+ contents of calcites are not very accurate indicators of environmental salinities. 相似文献
12.
Distribution and isotopic composition (δ13C) of low molecular weight hydrocarbon gases were studied in Big Soda Lake (depth = 64 m), an alkaline, meromictic lake with permanently anoxic bottom waters. Methane increased with depth in the anoxic mixolimnion (depth = 20–35 m), reached uniform concentrations (55 μM/l) in the monimolimnion (35–64 m) and again increased with depth in monimolimnion bottom sediments (>400 μM/kg below 1 m sub-bottom depth). The μ13C[CH4] values in bottom sediment below 1 m sub-bottom depth (<?70 per mil) increased with vertical distance up the core (δ13C[CH4] = ?55 per mil at sediment surface). Monimolimnion δ13C[CH4] values (?55 to ?61 per mil) were greater than most δ13C[CH4] values found in the anoxic mixolimnion (92% of samples had δ13C[CH4] values between ?20 and ?48 per mil). No significant concentrations of ethylene or propylene were found in the lake. However ethane, propane, isobutane and n-butane concentrations all increased with water column depth, with respective maximum concentrations of 260, 80, 23 and 22 nM/l encountered between 50–60 m depth. Concentrations of ethane, propane and butanes decreased with depth in the bottom sediments. Ratios of were high (250–620) in the anoxic mixolimnion, decreased to ~161 in the monimolimnion and increased with depth in the sediment to values as high as 1736. We concluded that methane has a biogenic origin in both the sediments and the anoxic water column and that C2-C4 alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in δ13C[CH4] and with depth in the water column and sediments are probably caused by bacteria] processes. These might include anaerobic methane oxidation and different rates of methanogenesis and C2 to C4 alkane production by microorganisms. 相似文献
13.
Calculations based on approximately 350 new measurements (CaT-PCO2) of the solubilities of calcite, aragonite and vaterite in CO2-H2O solutions between 0 and 90°C indicate the following values for the log of the equilibrium constants KC, KA, and KV respectively, for the reaction CaCO3(s) = Ca2+ + CO2?3: where T is in oK. At 25°C the logarithms of the equilibrium constants are ?8.480 ± 0.020, ?8.336 ± 0.020 and ?7.913 ± 0.020 for calcite, aragonite and vaterite, respectively.The equilibrium constants are internally consistent with an aqueous model that includes the CaHCO+3 and CaCO03 ion pairs, revised analytical expressions for CO2-H2O equilibria, and extended Debye-Hückel individual ion activity coefficients. Using this aqueous model, the equilibrium constant of aragonite shows no PCO2-dependence if the CaHCO+3 association constant is between 0 and 90°C, corresponding to the value logKCahco+3 = 1.11 ± 0.07 at 25°C. The CaCO03 association constant was measured potentiometrically to be between 5 and 80°C, yielding logKCaCO03 = 3.22 ± 0.14 at 25°C.The CO2-H2O equilibria have been critically evaluated and new empirical expressions for the temperature dependence of KH, K1 and K2 are , and logK2 = ?107.8871 ? 0.03252849T + 5151.79/T + 38.92561 logT ? 563713.9/T2 which may be used to at least 250°C. These expressions hold for 1 atm. total pressure between 0 and 100°C and follow the vapor pressure curve of water at higher temperatures.Extensive measurements of the pH of Ca-HCO3 solutions at 25°C and 0.956 atm PCO2 using different compositions of the reference electrode filling solution show that measured differences in pH are closely approximated by differences in liquid-junction potential as calculated by the Henderson equation. Liquid-junction corrected pH measurements agree with the calculated pH within 0.003-0.011 pH.Earlier arguments suggesting that the CaHCO+3 ion pair should not be included in the CaCO3-CO2-H2O aqueous model were based on less accurate calcite solubility data. The CaHCO+3 ion pair must be included in the aqueous model to account for the observed PCO2-dependence of aragonite solubility between 317 ppm CO2 and 100% CO2.Previous literature on the solubility of CaCO3 polymorphs have been critically evaluated using the aqueous model and the results are compared. 相似文献
14.
The olivine-ilmenite thermometer of Andersen and Lindsley (1979) was based on an incorrect formulation for the excess free energy of an asymmetric ternary solution. A valid formulation is derived and used to revise the parameters of the olivine-ilmenite thermometer. For olivine and ilmenite that have equilibrated above 700°C, temperature can be calculated from: with . The revised model gives Wil·gkG = 5767?3.09T + 0.011P and ΔGexch = 7301 ? 8.9T ? 0.047P (T in K, P in bars). Applications include Apollo 17 breccias and kimberlites. 相似文献
15.
A reevaluation of the entropy and Gibbs free energy of formation of Al3+(aq) yields ?308 ± 15 J/K·mol and 489.4 ± 1.4kj/mol for S0298 and respectively. The standard electrode potential for aluminum is 1.691 ± 0.005 volts. 相似文献
16.
In a soil developed on the Cretaceous chalk of the Eastern Paris basin, calcite dissolution begins at the surface. The soil water is rapidly saturated in calcite. Calcite dissolution follows two different pathways according to seasonal pedoclimatic conditions.During winter: the soil is only partly saturated in water and the CO2 partial pressure is low (Ca 10?3 atm.). As a consequence total inorganic dissolved carbon (TIDC) is a hundred times the carbon content of the gaseous phase. Equilibrium is usually observed between the two phases. It is a closed system. The measured carbon 14 activity (87,5%) and 13C content () of the drainage water are very close to theoretical values calculated for an ideal mixing system between gaseous and mineral phases (respectively characterized by the following isotopic values: ; ; ; ).During spring and summer: the soil moisture decreases, the input of biogenic CO2 induces an increase of the soil CO2 partial pressure (Ca from 3.10?3 atm to 7.10?3 atm). The carbon content of the gaseous phase is higher by an order of magnitude compared to winter conditions. Therefore the aqueous phase is undersaturated in CO2 with respect to the latter. This disequilibrium occurs as a result of unbalanced rates of CO2 dissolution and CO2 effusion toward atmosphère. It is an open system. The carbon isotopic ratio of the aqueous phase is regulated by that of the gaseous phase, as demonstrated by the agreement between measured and calculated isotopic compositions (respectively δL mes = from ?9,4%0 to ?11,5%0, δl calc = from ?9,8%0 to ?13,9%0 AL mes = 119%, AL calc = from 119% to 125%).The solutions originating from both systems (open and closed) move downwards without significant mixing together. It has also been observed that no significant variation of the TIDC isotopic composition occurs during precipitation of secondary calcite. 相似文献
17.
Experimental quartz solubilities in H2O (Anderson and Burnham, 1965, 1967) were used together with equations of state for quartz and aqueous species (Helgesonet al., 1978; Walther and Helgeson, 1977) to calculate the dielectric constant of H2O () at pressures and temperatures greater than those for which experimental measurements (Heger, 1969; Lukashovet al., 1975) are available ( and ). Estimates of computed in this way for 2 kb (which are the most reliable) range from 9.6 at 600°C to 5.6 at 800°C. These values are 0.5 and 0.8 units greater, respectively, than corresponding values estimated by Quist and Marshall (1965), but they differ by <0.3 units from extrapolated values computed from Pitzer's (1983) adaptation of the Kirkwood (1939) equation. The estimates of generated from quartz solubilities at 2 kb were fit with a power function of temperature, which was then used together with equations and data given by Helgeson and Kirkham (1974a,b, 1976) Helgesonet al. (1981), and Helgeson (1982b, 1984) to calculate Born functions, Debye Hückel parameters, and the thermodynamic properties of Na+, K+, Mg++, Ca++, and other aqueous species of geologic interest at temperatures to 900°C. 相似文献
18.
N Guilhaumou P Dhamelincourt J-C Touray J Touret 《Geochimica et cosmochimica acta》1981,45(5):657-673
Optical and analytical studies were performed on 400 N2 + CO2 gas bearing inclusions in dolomites and quartz from Triassic outcrops in northern Tunisia. Other fluids present include brines (NaCl and KCl bearing inclusions) and rare liquid hydrocarbons. At the time of trapping, such fluids were heterogeneous gas + brine mixtures. In hydrocarbon free inclusions the mole ratio was determined using two different non-destructive and punctual techniques: Raman microprobe analysis, and optical estimation of the volume ratios of the different phases selected at low temperatures. In the observed range of compositions, the two methods agree reasonably well.The N2 + CO2 inclusions are divided into three classes of composition: (a) : Liquid nitrogen is always visible at very low temperature and homogenisation occurs in the range ?151°C to ? 147°C (nitrogen critical temperature) dry ice (solid CO2) sublimates between ?75°C and ?60°C; (b) : liquid nitrogen is visible at very low temperature but dry ice melts on heating; liquid and gas CO2 homogenise to liquid phase between ?51°C to ?22°C; (c) : liquid nitrogen is not visible even at very low temperature (?195°C) and liquid and gas CO2 homogenise to liquid phase between ?22°C and ?15°C. The observed phases changes are used to propose a preliminary phase diagram for the system CO2-N2 at low temperatures.Assuming additivity of partial pressures, isochores for the CO2-N2 inclusions have been computed. The intersection of these isochores with those for brine inclusions in the same samples may give the P and T of trapping of the fluids. 相似文献
19.
The spectrophotometric measurements of chloro complexes of lead in aqueous HCl, NaCl, MgCl2 and CaCl2 solutions at 25°C have been analyzed using Pitzer's specific interaction equations. Parameters for activity coefficients of the complexes PbCl+, PbCl20 and PbCl3? have been determined for the various media. Values of , and were obtained for the cumulative formation constants. []. These values are in reasonable agreement with literature data. The Pitzer parameters for the PbCl ion pairs in various media were used to calculate the speciation of Pb2+ in an artificial seawater solution. 相似文献
20.
Frank J Millero 《Geochimica et cosmochimica acta》1979,43(10):1651-1661
The apparent constants (K'i) for the ionization of carbonic acid in seawater at various salinities (S,%.) have been fit to equations of the form ln whereKi is the thermodynamic ionization constant in water, Ai, and Bi are adjustable parameters. The temperature dependence (TK) of Ki, Ai and Bi were of the form, a0 + a1/T + a3 ln T. Equations of similar forms have been used to analyze the ionization constants for water and boric acid and the solubility product of calcite in seawater. The effect of pressure on the apparent constants () have been fit to equations of the form ln where the volume (ΔV) and compressibility (ΔK) changes are polynomial functions of temperature. The equations generated for various açids in seawater have been used to examine the carbonate system in seawater. Equations relating the NBS and Tris pH scales have been derived as well as equations of pH as a function of temperature and pressure. The equations from Hansson (1972, Ph.D. Thesis, University of Göteborg, Sweden) and Mehrbachet al. (1973, Limnol. Oceanogr.18, 897–907) have been used to examine the components of the carbonate system. At a fixed total alkalinity and total carbon dioxide, differences of ±0.01 m-equiv kg?1 in HCO?3 and CO2?3 were found; however, the [CO2] and Pco2 are nearly the same. The contribution of borate ion, B(OH)?4 determined from the equations of Hansson (1972, Ph.D. Thesis, University of Göteborg, Sweden) and Lyman (1957, Ph.D. Thesis, University of California, Los Angeles) differ by ±0.01 m-equiv kg?1 for waters with the same salinity and temperature. 相似文献