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1.
Direct measurements on water samples from several CO2-charged warm springs are significantly higher than values calculated from field pH and alkalinity (and other constituents). In addition, calcite saturation indices calculated from field pH and solution composition indicated supersaturation in samples which, on the basis of hydrogeologic concepts, should be near saturation or undersaturated. We attribute these discrepancies to uncertainties in field pH, resulting from CO2 outgassing during pH measurement. Because samples for direct measurement can be taken with minimal disturbance to the water chemistry, we have used the measured to back calculate an estimate of the field pH and the carbon isotopic composition of the water before outgassing. By reconstructing water chemistry in this way, we find generally consistent grouping of , pH, and degree of calcite saturation in samples taken from the same source at different times, an observation which we expect based on our understanding of the hydrogeology and geochemistry of the ground-water systems. This suggests that for very careful geochemical work, particularly on ground-waters much above ambient temperature, measurements may provide more information on the system and a better estimate of its state of saturation with respect to carbonate minerals than can field measurements of pH. 相似文献
2.
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
3.
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
4.
Diffusion of ions in sea water and in deep-sea sediments 总被引：3，自引：0，他引：3
Sandra Gregory 《Geochimica et cosmochimica acta》1974,38(5):703-714
The tracer-diffusion coefficient of ions in water, Dj0, and in sea water, , differ by no more than zero to 8 per cent. When sea water diffuses into a dilute solution of water, in order to maintain the electro-neutrality, the average diffusion coefficients of major cations become greater but of major anions smaller than their respective or Dj0 values. The tracer diffusion coefficients of ions in deep-sea sediments, Dj,sed., can be related to by , where θ is the tortuosity of the bulk sediment and a a constant close to one. 相似文献
5.
Joan D. Willey 《Geochimica et cosmochimica acta》1982,46(7):1307-1310
Measurement of solubility as a function of pressure allows calculation of . Using this experimental approach, the best estimate of for the dissolution of aged amorphous silica in salt water or seawater at 0–2°C is ?9.9 cm3 mol?1 (standard error = 0.4 cm3 mol?1). This gives , which compares well with other published values of . 相似文献
6.
We have calculated the total individual ion activity coefficients of carbonate and calcium, and , in seawater. Using the ratios of stoichiometric and thermodynamic constants of carbonic acid dissociation and total mean activity coefficient data measured in seawater, we have obtained values which differ significantly from those widely accepted in the literature. In seawater at 25°C and 35%. salinity the (molal) values of and are and , respectively. These values of and are independent of liquid junction errors and internally consistent with the value . By defining and on a common scale (), the product is independent of the assigned value of and may be determined directly from thermodynamic measurements in seawater. Using the value and new thermodynamic equilibrium constants for calcite and aragonite, we show that the apparent constants of calcite and aragonite are consistent with the thermodynamic equilibrium constants at 25°C and 35%. salinity. The demonstrated consistency between thermodynamic and apparent constants of calcite and aragonite does not support a hypothesis of stable Mg-calcite coatings on calcite or aragonite surfaces in seawater, and suggests that the calcite critical carbonate ion curve of Broecker and Takahashi (1978, Deep-Sea Research25, 65–95) defines the calcite equilibrium boundary in the oceans, within the uncertainty of the data. 相似文献
7.
Selective wettability and floatability of several inherently hydrophobic minerals have been investigated using aqueous methanol solutions of various surface tensions. The relationship between the critical surface tension of wetting, , and of floatability, , of the samples is examined. Experimental evidence is provided to show that a flotation feed cannot be represented by an uniquely defined value. It is appropriate to specify for an inherently hydrophobic solid a critical surface tension range of floatability with upper and lower limits, and respectively. The particles which are predominated by cleavage or crystal faces determine the lower limit, while those with some threshold degree of ionic character determine the upper limit. Examples of separation tests presented demonstrate that in the case of equality between values of two inherently floatable solids (or their values), a difference in values determines the efficiency of their separation. It is also shown that the interfacial tension of maximum separation efficiency may be predicted from the individual surface tension of floatability curves which may be represented by second-order functions. 相似文献
8.
The partial molal volume of silicic acid () in 0.725 M NaCl at 1°C was calculated from the measured volume change (Δ) due to the neutralization of anhydrous sodium metasilicate with HCl and the and obtained from the literature. , determined under experimental conditions of pH = 2.2, compares favorably with calculated from the measured volume change due to the hydrolysis of the meta-silicate salt at pH = 11 and from the partial molal volume due to electrostriction () of water by charged Si species present in the solution at the high pH. This agreement lends support to a semiempirical model for calculating in developed by Millero (1969). in 0.725 M NaCl needed for this calculation was also determined in this work. The rate of polymerization of Si(OH)4 at 1°C was monitored to insure that the monomer Si(OH)4 was the main Si species present during the determination of by neutralization of the alkali silicate. determined in this study compares favorably with the value calculated from high pressure solubility measurements. 相似文献
9.
Polyunsaturated fatty acids (C18:2 and C18:3ω3 were analyzed in the upper 20m layer of a 200 m long sediment core taken from Lake Biwa. Concentration maxima occur in layers at depths of 0.2, 1–5, 11–12, and 16m. The vertical changes in the ratio appear to correlate with paleoclimatic condition suggested from palynological evidence. On the basis of ratios, it was suggested that it has been colder at 200, 1000–4000, 15,000 and 20,000 yr BP than at other times. 相似文献
10.
The partial molal volume () of silicic acid in 0.725 m NaCl at 20°C has been calculated from (1) direct volume changes due to the dissolution of anhydrous sodium silicate and (2) some literature values for the partial molal volumes of NaOH and water. , unconnected for electrostriction effects, was found to be 53 ± 2 ml mole?1. , corrected for volume changes due to solvent electrostriction by charged Si species, was estimated to be in the range 58–62 ml mole?1; this range is 7–11 ml mole?1 greater than the calculated from Willey's (Mar. Chem. 2, 239–250, 1974) solubility data obtained from the dissolution, in seawater, of amorphous silica subjected to hydrostatic pressure. Our does, however, agree within experimental error with the calculated from Jones and Pytkowicz's (Bull. Soc. Roy. Sci. Liege 42, 118–120, 1973) data for the solubility of amorphous silica in seawater at high pressure and is nearly in agreement with Willey's (Ph.D. thesis, Dalhousie University, 1975) solubility data for amorphous silica in 0.6 m NaCl. 相似文献
11.
Frank J Millero 《Geochimica et cosmochimica acta》1981,45(11):2085-2089
The stoichiometric, , and apparent, K'HA, constants for the ionization of a number of weak acids (NH4+, HSO4?, HF, H2O, B(OH)3, H2CO3, HCO3?, H3PO4, H2PO4?, HPO42, H3AsO4 H2AsO4? and HAsO42?) in seawater at 25°C diluted with water have been fitted to equations of the form (Millero, 1979). In where In KHA is the thermodynamic constant in water, S is the salinity, A and B are adjustable parameters. The validity of this equation in estuarine waters has been examined by using an ion pairing model (Millero and Schreiber, 1981). The calculated values of and K'HA at S = 35%. are in good agreement with the measured values for all the systems examined. The equation used to extrapolate the measured values to pure water KHA predicted values that agreed with those determined by using the ion pairing model. The exception was the ionization of HPO42? due to the strong interactions of Ca2+ and Mg2+ with PO43?. The differences in the predicted values of in seawater diluted with pure water and average river water were very small for all the acids except HPO42? (the maximum ΔpK = 0.96 in average river water). The larger difference in the for HPO42? in river waters is due to the strong interactions of Ca2+ and PO43?. 相似文献
12.
C.C Harris A Chakravarti S.N Degaleesan 《International Journal of Mineral Processing》1975,2(1):39-58
Residence time measurements were made on a Denver laboratory flotation machine with and without the DR ring assembly. Soluble and insoluble tracers were used (a dye and fine quartz, respectively), and the variables studied were tank liquid volume, , water and air volumetric flow rates, Q and QA respectively, and some geometric and design variables.By analogy with nominal residence time, , a term “effective residence time” is defined by: where f(t) is the fraction of tracer remaining in the tank at time t. Perfect mixing is indicated if and only if: (i) data satisfies the exponential relationship; and (ii) .Using the soluble tracer the machine behaved substantially as a perfect mixer under all operating conditions, except with the DR ring at values of QA nearly double the natural aeration capacity of the machine; condition (i) above was satisfied, but .With the insoluble tracer the machine behaved as a perfect mixer only without air. As QA increased, increased from unity to about 1.2, and the effect was emphasized by the DR ring. In all cases condition (i) above was satisfied.A model in which the flow pattern in the tank includes a large component of pulp recirculation through the impeller region is developed. This model can account for the experimental findings but the details remain to be elucidated. 相似文献
13.
Tadao Nishiyama 《Geochimica et cosmochimica acta》1983,47(2):283-294
This paper describes an application of a steady diffusion model (Joesten, 1977) to an olivineplagioclase corona and some new results about a theoretical background on the steady diffusion equations.The olivine-plagioclase corona in a metanorite from Mt. Ikoma. Japan, has a layer sequence of olivinecummingtonite-hornblende + spinel-plagioclase. An analysis of a set of steady diffusion equations for the corona in the four-component system, MgO-AlO-SiO2-Na0.1Ca0.9O0.95 (NC) with excess H2O. successfully gives the exchange cycle (Fisher, 1973) in the layer sequence with specific values of the phenomenological coefficients' ratios; , and . The factor which controls most strictly the stability of the layer sequence under isobaric-isothermal conditions is .Theoretical considerations on the steady diffusion equations show that the L-ratios does not depend on concentrations even if the phenomenological coefficients themselves are functions of concentrations. Equivalence of the steady state condition and the minimum rate of entropy production law (Prigogine, 1967) is also proved for the system with fixed chemical potential gradients under isobaric-isothermal conditions, such as reaction bands. These results give a strong background for the model. 相似文献
14.
A new technique for the determination of intrinsic oxygen fugacities () of single and polyphase geological samples with solid ZrO2, oxygen-specific electrolytes is described. Essentially the procedure involves isolating the emf signal from the sample from that unavoidably imposed by the residual atmosphere inside the sample-bearing sensor. By varying the of the residual atmosphere, it is possible to determine a ‘plateau’ value of constant recorded from the sensor which represents a reversed intrinsic measurement for the sample alone, and where the extent of the plateau reflects the innate buffering capability of the sample. A measure of the precision and accuracy of the data obtained is the fact that identical values are obtained whether on a heating or cooling cycle of the sample + compatible atmosphere system.These techniques have been applied to measurements of the intrinsic of spinels from peridotites and megacryst assemblages from Australia, West Germany and the U.S.A. Oxidation states range from ～- 0.25 log10 units more oxidized to 1 log10 unit more reduced than the iron-wüstite (IW) buffer. The overall reduced nature of the spinels and the range of 's obtained are striking features of the data. One implication of the results is that the majority of mantle-derived magmas are initially highly reduced, and the relatively oxidized values observed at surface (～- 4–5 log10 orders more oxidized than IW) reflect late-stage alteration, perhaps by H2 loss (Sato, 1978). 相似文献
15.
William E. Glassley 《Geochimica et cosmochimica acta》1983,47(3):597-616
Compositional differences between granulite facies rocks and equivalent amphibolite facies rocks and the observation of CO2-rich fluid inclusions in granulites, have led to the suggestion that CO2 must play a role in modifying the composition of deep continental crust. How CO2 effects this change has remained unclear. Using the thermodynamic properties of aqueous ions in a fluid of evolving ratio, it is possible to model the incongruent dissolution of feldspars under conditions appropriate for granulite facies metamorphism. The results demonstrate that dissolution will be strongly enhanced at high ratios, with ion solubilities being Na+ >K+ ? Ca++. This enhancement is compatible with the reported compositional contrasts between granulite and amphibolite facies rock, but requires large fluid volumes.To test the dissolution model, a detailed field and petrologic study was conducted in a well exposed granulite facies terrane in West Greenland. Strong correlation between fluid composition and bulk rock chemistry can be documented; CO2-rich regions contain rocks which consistently have low ratios, while H2O-rich regions consistently have high ratios. Magnetite rims on sulfide grains are ubiquitous in high regions and are absent in high regions, and they provide evidence that CO2 was introduced into the region. These correlations and observations are predictable from the properties of the dissolution process. These considerations, along with observations regarding graphite petrogenesis, provide strong arguments that the total fluid volume interacting with the rock during metamorphism was very large, in some cases equaling or exceeding total rock volume. Such large fluid volumes can lead to significant compositional modification of the crust, and will mask the original protolith chemistry. Such processes should lead to Ca- and Al-enriched, Na-, K-, S- and Si-depleted residues in the deep crust. 相似文献
16.
Constant M.G. van den Berg 《Geochimica et cosmochimica acta》1984,48(12):2613-2617
The stability constants, , for borate complexes with the ions of Cu, Pb, Cd and Zn are determined in this work by DPASV in 0.7 M KNO3 at metal concentrations of 10?7 M. The acidity constants of the Cu2+ ion are determined by DPASV in the same conditions. The following values for log () have been obtained: CuB: 3.48, CuB2: 6.13, PbB: 2.20, PbB2: 4.41, ZnB: 0.9, ZnB2: 3.32, CdB: 1.42, and CdB2: 2.7, while the values for the acidity constants of Cu are and . At the low concentration of boron in 35%. S sea-water complexes with borate represent only about 0.2% Cu, 0.03% Pb, 0.02% Zn and 0.003% Cd. 相似文献
17.
J.R Holloway 《Geochimica et cosmochimica acta》1973,37(3):651-666
The stability of the amphibole pargasite [NaCa2Mg4Al(Al2Si6))O22(OH)2] in the melting range has been determined at total pressures (P) of 1.2 to 8 kbar. The activity of H2O was controlled independently of P by using mixtures of H2O + CO2 in the fluid phase. The mole fraction of H2O in the fluid () ranged from 1.0 to 0.2.At P < 4 kbar the stability temperature (T) of pargasite decreases with decreasing at constant P. Above P ? 4 kbar stability T increases as is decreased below one, passes through a T maximum and then decreases with a further decrease in . This behavior is due to a decrease in the H2O content of the silicate liquid as decreases. The magnitude of the T maximum increases from about 10°C (relative to the stability T for ) at P = 5 kbar to about 30°C at P = 8 kbar, and the position of the maximum shifts from at P = 5 kbar to at P = 8 kbar.The H2O content of liquid coexisting with pargasite has been estimated as a function of at 5 and 8 kbar P, and can be used to estimate the H2O content of magmas. Because pargasite is stable at low values of at high P and T, hornblende can be an important phase in igneous processes even at relatively low H2O fugacities. 相似文献
18.
The cordierite-gedrite-cummingtonite rocks occur in the zone of sulphide mineralization. Field and petrographic evidences suggest formation of these rocks from the schists which are associated with them. Time relations between crystallization and deformation, as evident by textural relations, suggest that this transformation constitutes a progressive sequence in time during prograde metamorphism in the area. Bulk chemical compositions of the cordierite-gedrite-cummingtonite rocks plot in the compositional range of the chlorite schists in the AKF, ACF and AFM diagrams. The AFM diagram shows a discontinuity in the topology as revealed by the intersection of the coexisting garnet-chlorite join with the three-phase field of cordierite-gedrite-garnet, suggesting the reaction: . The reaction took place under conditions of , brought about by dilution of pore fluid by B, Cl, F, S, etc., which reduce the activity of water. 相似文献
19.
Equations are developed for calculating the density of aluminosilicate liquids as a function of composition and temperature. The mean molar volume at reference temperature Tr, is given by , where the summation is taken over all oxide components except A12O3, X stands for mole fraction, terms are constants derived independently from an analysis of volume-composition relations in alumina-free silicate liquids, and is the composition-dependent apparent partial molar volume of Al2O3. The thermal expansion coefficient of aluminosilicate liquids is given by , where terms are constants independent of temperature and composition, and is a composition-dependent term representing the effect of Al2O3 on the thermal expansion. Parameters necessary to calculate the volume of silicate liquids at any temperature T according to V(T) = Vrexp[α(T-Tr)], where Tr = 1400°C have been evaluated by least-square analysis of selected density measurements in aluminosilicate melts. Mean molar volumes of aluminosilicate liquids calculated according to the model equation conform to experimentally measured volumes with a root mean square difference of 0.28 and an average absolute difference of 0.90% for 248 experimental observations. The compositional dependence of is discussed in terms of several possible interpretations of the structural role of Al3+ in aluminosilicate melts. 相似文献
20.
The fractionation factors () for the reduction of CO2 to CH4 by pure cultures of methane-producing bacteria are, for Methanosarcina barkeri at 40°C, 1.045 ± 0.002; for Methanobacterium strain M.o.H. at 40°C, 1.061 ± 0.002; and, for Methanobacterium thermoautotrophicum at 65°C, 1.025 ± 0.002. These observations suggest that the acetic acid used by acetate dissimilating bacteria, if they play an important role in natural methane production, must have an intramolecular isotopic fractionation () approximating the observed fractionation. 相似文献