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1.
The dissolution kinetics of a simulated lunar glass were examined at pH 3, 5, and 7. Additionally, the pH 7 experiments were conducted in the presence of citric and oxalic acid at concentrations of 2 and 20 mM. The organic acids were buffered at pH 7 to examine the effect of each molecule in their dissociated form. At pH 3, 5, and 7, the dissolution of the synthetic lunar glass was observed to proceed via a two-stage process. The first stage involved the parabolic release of Ca, Mg, Al, and Fe, and the linear release of Si. Dissolution was incongruent, creating a leached layer rich in Si and Ti which was verified by transmission electron microscopy (TEM). During the second stage the release of Ca, Mg, Al, and Fe was linear. A coupled diffusion/surface dissolution model was proposed for dissolution of the simulated lunar glass at pH 3, 5, and 7. During the first stage the initial release of mobile cations (i.e., Ca, Mg, Al, Fe) was limited by diffusion through the surface leached layer of the glass (parabolic release), while Si release was controlled by the hydrolysis of the Si-O-Al bonds at the glass surface (linear release). As dissolution continued, the mobile cations diffused from greater depths within the glass surface. A steady-state was then reached where the diffusion rate across the increased path lengths equalled the Si release rate from the surface. In the presence of the organic acids, the dissolution of the synthetic lunar glass proceeded by a one stage process. The release of Ca, Mg, Al, and Fe followed a parabolic relationship, while the release of Si was linear. The relative reactivity of the organic acids used in the experiments was citrate > oxalate. A thinner leached layer rich in Si/Ti, as compared to the pH experiments, was observed using TEM. Rate data suggest that the chemisorption of the organic anion to the surface silanol groups was responsible for enhanced dissolution in the presence of the organic acids. It is proposed that the increased rate of Si release is responsible for the one stage parabolic release of mobile cations and the relatively thin leached layer compared to experiments at pH 3 and 5. 相似文献
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Dissolution experiments of a tholeiite basalt glass carried out at different pH and T (up to 300°C) using a rotatingdisc apparatus show that, depending on pH and T, dissolution can be controlled by one of the following steps: (1) surface reaction; (2) transport of reactants in solution; and (3) mixed reaction. The activation energies of these different processes were found to be 60, 9 and 15–50 kJ mol−1, respectively. Taking account of these results, it appears likely that surface reactions are not rate limiting for the hydrolysis of most crystalline silicate minerals in hydrothermal and metamorphic processes, and that caution should be exercised when predicting rate of reactions at high temperatures solely on the basis of activation energies measured at low temperatures.
Comparison of experimental and theoretical potentiometric titrations of the basalt glass and its constituent oxides indicates that the adsorption of H+ and OH− ions at the basalt surface is metal cation specific and that the net adsorption can be predicted from the sole knowledge of the acidity constants of the network-forming constituent oxides. We found that in the acidic pH region dissolution is promoted by the adsorption of H+ on al and Fe surface sites while in the basic region, dissolution is promoted by the adsorption of OH− on Si sites. The combination of the two distinct types of surface sites, Al and Fe on the one hand, and Si on the other hand, results in a dissolution rate minimum at a pH-value between the pHzpc of the two groups of oxide components. Linear regressions with a slope n=3.8 are observed both in acid and alkaline solutions in logarithmic plots of the rate of dissolution vs. the surface charge. The value of n, which represents the number of protonation or hydroxylation steps prior to metal detachment, has been found equal to the mean valence of the network-forming metals.
Combining concepts of surface coordination chemistry with transition state theory afforded characterisation of the activated complexes involved in basalt dissolution processes. From the values obtained for the thermodynamic properties of activation for basalt dissolution it is assumed that the activated complexes formed during the H2O-promoted dissolution of the basalt glass are more tightly bonded than those formed during H+- or OH−-promoted dissolution. 相似文献
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The aim of this study was to use Monte Carlo simulations to provide atomic-level insights into the dissolution behavior of borosilicate and aluminoborosilicate glasses in dilute aqueous solutions. In the first part of this work, the effects of different structural features, such as the presence of non-bridging oxygens (NBO) or the formation of boroxol rings, on glass dissolution were evaluated separately and led to the following conclusions. (1) The dependence of the dissolution rate on the amount of NBO was found to be linear at all Si/B ratios and the accelerating effect of NBO was shown to increase with increasing Si/B ratio. (2) The formation of boroxol rings and of clusters of boroxol rings resulted in an increase of the dissolution rate at all Si/B ratios and, again, the extent of the rate increase was strongly dependent on the Si/B ratio. (3) For aluminosilicate glasses, the implementation of the aluminum avoidance rule was found to increase the rate of dissolution relative to that obtained for a random distribution.In the second part of this work, the dissolution of the NeB glasses studied by Pierce et al. (2010) was modeled in dilute aqueous solutions. Pierce et al. concluded from their study that either the rupture of the Al-O bonds or that of the Si-O bonds was the rate-limiting step controlling the dissolution of the NeB glasses. The simulations refined this conclusion and showed that, at low B/Al ratios, the rupture of both Al-O-Si and Si-O-Si linkages contributed to the dissolution rate whereas, at high B/Al ratios, the dissolution rate was independent of the rupture of Al-O-Si linkages and was controlled by S1 sites (silicon sites at the glass-water interface with one connection to nearest-neighbor sites) and dissolution via detachment of clusters. 相似文献
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Comparison of measured far-from-equilibrium dissolution rates of natural glasses and silicate minerals at 25 °C and pH 4 reveals the systematic effects of crystallinity and elemental composition on these rates. Rates for both minerals and glasses decrease with increasing Si:O ratio, but glass dissolution rates are faster than corresponding mineral rates. The difference between glass and mineral dissolution rates increases with increasing Si:O ratio; ultra-mafic glasses (Si:O ? 0.28) dissolve at similar rates as correspondingly compositioned minerals, but Si-rich glasses such as rhyolite (Si:O ∼ 0.40) dissolve ?1.6 orders of magnitude faster than corresponding minerals. This behaviour is interpreted to stem from the effect of Si-O polymerisation on silicate dissolution rates. The rate controlling step of dissolution for silicate minerals and glasses for which Si:O > 0.28 is the breaking of Si-O bonds. Owing to rapid quenching, natural glasses will exhibit less polymerisation and less ordering of Si-O bonds than minerals, making them less resistant to dissolution. Dissolution rates summarized in this study are used to determine the Ca release rates of natural rocks at far-from-equilibrium conditions, which in turn are used to estimate their CO2 consumption capacity. Results indicate that Ca release rates for glasses are faster than those of corresponding rocks. This difference is, however, significantly less than the corresponding difference between glass and mineral bulk dissolution rates. This is due to the presence of Ca in relatively reactive minerals. In both cases, Ca release rates increase by ∼two orders of magnitude from high to low Si:O ratios (e.g., from granite to gabbro or from rhyolitic to basaltic glass), illustrating the important role of Si-poor silicates in the long-term global CO2 cycle. 相似文献
7.
不同pH值条件下石英溶解的分子机理 总被引：3，自引：0，他引：3
对于石英-水反应体系,石英表面的Si-O-Si键的水解断裂是溶解反应过程的关键步骤。采用高级分子轨道从头计算法,研究了不同pH值下石英表面Q1（Si）位置的溶解反应动力学过程。对反应过程的势能面、过渡态、反应路径进行了量子化学计算（包括使用从头计算的分子动力学方法）,结果表明：（1）酸性条件下,H^＋连接的是石英表面末端Si-0H上的非桥氧,而非Si-O-Si键上的桥氧,这一链接反而增强了Si—O—Si键;（2）在中性和酸性条件下,石英溶解反应的速度控制步是Q1（Si）—Obr的断裂过程,而碱性条件下反应速率却由水分子靠近Q1（Si）的过程控制,它比Q1（Si）-Obr的断裂过程更慢;（3）活化能计算数据表明,碱性条件下石英溶解速率会随着pH值的增大而迅速增大;相对照的是,在酸性条件下,溶解速率与中性条件时相比变化不大,甚至还略有降低。本文纠正了一些关于石英溶解机理的长期的错误认识,比如前人错误地认为在酸性条件下首先形成Si-O（H^＋）-Si形式的复合物,然后Si-O-Si发生断裂。本研究结果表明,实际上是形成Si—O—Si-OH2^＋…H2O形式的过渡态复合物。然后Si-O-Si发生断裂。前人模型的结果与实验结果分歧,是一个长期遗留的困惑,而本文发现的断键机理模型及其计算结果,可以很好地与不同pH值下石英溶解的实验数据吻合。 相似文献
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《Geochimica et cosmochimica acta》1987,51(9):2559-2568
The effect of oxalate, a strong chelator for Al and other cations, on the dissolution rates of oligoclase feldspar and tremolite amphibole was investigated in a flow-through reactor at 22°C. Oxalate at concentrations of 0.5 and 1 mM has essentially no effect on the dissolution rate of tremolite, nor on the steady-state rate of release of Si from oligoclase. The fact that oxalate has no effect on dissolution rate suggests that detachment of Si rather than Al or Mg is the rate-limiting step. At pH 4 and 9, oxalate has no effect on the steady-state rate of release of Al, and dissolution is congruent. At pH 5 and 7, oligoclase dissolution is congruent in the presence of oxalate, but in the absence of oxalate Al is preferentially retained in the solid relative to Si.Large transient “spikes” of Al or Si are observed when oxalate is added to or removed from the system. The cause of the spikes is unknown; we suggest adsorption on feldspar surfaces away from sites of active dissolution as a possibility. Solutions in the reactors are undersaturated with respect to both gibbsite and kaolinite, so neither the spikes nor the incongruent dissolution can be explained by formation of a secondary precipitate.The rate of dissolution of tremolite is independent of pH over the pH range 2–5, and decreases at higher pH. The rate of dissolution of oligoclase in our experiments was independent of pH over the pH range 4–9. Since the dissolution rate of these minerals is independent of pH and organic ligand concentration, the effect of acid deposition from the atmosphere on the rate of supply of cations from weathering of granitic rocks should be minor. 相似文献
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《Applied Geochemistry》1994,9(3):255-269
The initial dissolution kinetics of the French “R7T7” inactive LWR reference glass was investigated in organic media at 90°C by static experiments at imposed pH values. Tests were conducted with various organic acids or acid salts (formic acid, citric acid, humic acids, sodium citrate and sodium formate) at different concentrations and at pH values ranging from 3 to 9. The leachates were submitted to ICP-AES analysis, and the alteration films on the glass specimens were examined by SEM (equipped with an energy-dispersive chemical analysis systm) and XRD. Results are discussed for the following areas.Effect of pH: different mechanisms are involved at pH 2.5 and pH 9, but in both cases, the R7T7 glass dissolution kinetics are always controlled by a surface reaction mechanism. The most significant effects of the organic acids on the glass dissolution kinetics were observed at pH 3, which was not unexpected.Nature of the acid (or acid salt): this is an essential parameter. Formic acid (monoacid) and sodium formate had no effect on the initial glass dissolution rate nor on the nature of the alteration film; conversely, citric acid (triacid) and sodium citrate significantly affected glass dissolution. The role of citric acid in the surface reaction mechanism has been demonstrated experimentally at pH 2.5; it is also known to favor that extraction of Si (directly or indirectly) and Zr and probably of Fe. The humic acids are strong catalysts of the R7T7 glass dissolution reaction. The conclusions drawn from these observations corroborate other published findings, suggesting that the catalytic effect is appreciable only for species with at least two carboxylic acid functions.Effect of concentration: the effect of the concentration was observed at basic pH values in the presence of sodium citrate and humic acids. This parameter may thus be quantified and incorporated in the glass dissolution kinetic law. 相似文献
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Barry R. Bickmore Kathryn L. Nagy A. Riley Brinkerhoff 《Geochimica et cosmochimica acta》2006,70(2):290-305
The influence of Al(OH)4− on the dissolution rate of quartz at pH 10-13 and 59-89 °C was determined using batch experiments. Al(OH)4− at concentrations below gibbsite solubility depressed the dissolution rate by as much as 85%, and this effect was greater at lower pH and higher Al(OH)4− concentration. Dissolution rates increased with increasing temperature; however, the percent decrease in rate due to the presence of Al(OH)4− was invariant with temperature for a given H+ activity and Al(OH)4− concentration. These data, along with what is known about Al-Si interactions at high pH, are consistent with Al(OH)4− and Na+ co-adsorbing on silanol sites and passivating the surrounding quartz surface. The observed pH dependence, and lack of temperature dependence, of inferred Al(OH)4− sorption also supports the assumption that the acid-base behavior of the surface silanol groups has only a small temperature dependence in this range. A Langmuir-type adsorption model was used to express the degree of rate depression for a given in situ pH and Al(OH)4− concentration. Incorporation of the rate data in the absence of aluminate into models that assume a first-order dependence of the rate on the fraction of deprotonated silanol sites was unsuccessful. However, the data are consistent with the hypothesis proposed in the literature that two dissolution mechanisms may be operative in alkaline solutions: nucleophilic attack of water on siloxane bonds catalyzed by the presence of a deprotonated silanol group and OH− attack catalyzed by the presence of a neutral silanol group. The data support the dominance of the second mechanism at higher pH and temperature. 相似文献
11.
Bergur Sigfusson Sigurdur R. Gislason Graeme I. Paton 《Journal of Geochemical Exploration》2006,88(1-3):321
Histic Andosol in Western Iceland was studied using laboratory based repacked microcosms conjointly with sampling of field soil solution. The main primary phase of the 205 cm thick soil profile was basaltic glass, allophane content ranged from 2 to 22 wt.% and the soil carbon content ranged from 11 to 42 wt.%. At constant temperature, the dissolution rate of the basaltic glass, and probably allophane and imogolite, was dictated by the aH+3 / aAl3+ activity ratio only, which in turn is governed by the pH, total dissolved Al and the anions capable of complexing Al3+; SO42−, F− and organic anions (DOC). Dissolution rate was slowed down by up to 20% by decreasing undersaturation in the field. Dissolution rate of basaltic glass was stable after an initial flushing event at the beginning of microcosm experiments. Predicted dissolution rates increased up to a factor of 7 and 30 by speciating Al3+ with oxalate in field and microcosms respectively. Speciation with oxalate generally had more effect in shallow horizons than deep horizons. 相似文献
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Brucite (Mg(OH)2) dissolution rate was measured at 25°C in a mixed-flow reactor at various pH (5 to 11) and ionic strengths (0.01 to 0.03 M) as a function of the concentration of 15 organic and 5 inorganic ligands and 8 divalent metals. At neutral and weakly alkaline pH, the dissolution is promoted by the addition of the following ligands ranked by decreasing effectiveness: EDTA ≥ H2PO4− > catechol ≥ HCO3− > ascorbate > citrate > oxalate > acetate ∼ lactate and it is inhibited by boric acid. At pH >10.5, it decreases in the presence of PO43−, CO32−, F−, oxine, salicylate, lactate, acetate, 4-hydroxybenzoate, SO42− and B(OH)4− with orthophosphate and borate being the strongest and the weakest inhibitor, respectively. Xylose (up to 0.1 M), glycine (up to 0.05 M), formate (up to 0.3 M) and fulvic and humic acids (up to 40 mg/L DOC) have no effect on brucite dissolution kinetics. Fluorine inhibits dissolution both in neutral and alkaline solutions. From F sorption experiments in batch and flow-through reactors and the analysis of reacted surfaces using X-ray Photoelectron Spectroscopy (XPS), it is shown that fluorine adsorption is followed by its incorporation in brucite lattice likely via isomorphic substitution with OH. The effect of eight divalent metals (Sr, Ba, Ca, Pb, Mn, Fe, Co and Ni) studied at pH 4.9 and 0.01 M concentration revealed brucite dissolution rates to be correlated with the water molecule exchange rates in the first hydration sphere of the corresponding cation.The effect of investigated ligands on brucite dissolution rate can be modelled within the framework of the surface coordination approach taking into account the adsorption of ligands on dissolution-active sites and the molecular structure of the surface complexes they form. The higher the value of the ligand sorption constant, the stronger will be its catalyzing or inhibiting effect. As for Fe and Al oxides, bi- or multidentate mononuclear surface complexes, that labilize Mg-O bonds and water coordination to Mg atoms at the surface, enhance brucite dissolution whereas bi- or polynuclear surface complexes tend to inhibit dissolution by bridging two or more metal centers and extending the cross-linking at the solid surface. Overall, results of this study demonstrate that very high concentrations of organic ligands (0.01-0.1 M) are necessary to enhance or inhibit brucite dissolution. As a result, the effect of extracellular organic products on the weathering rate of Mg-bearing minerals is expected to be weak. 相似文献
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This investigation was carried out to assess the protective properties of the alteration film that develops during aqueous alteration of the French SON 68 (R7T7-type) nuclear glass, notably by examining the behavior of some network-forming cations in the presence of complexing anions. Glass alteration was studied here in the presence of orthophosphate ions. Comparisons were established between two series of tests performed with a solution containing orthophosphate ions and control tests performed under the same conditions but without phosphates. The first series of experiments was performed under initial rate conditions (i.e. in dilute media) to assess the effect of pH and phosphate concentration on the initial glass dissolution rate. Under these conditions, which ensure maximum chemical affinity of the glass dissolution reaction, phosphate adsorption occurs at the reaction interface only with acid pH values, at which the glass dissolution reaction is strongly inhibited. The elements that form complexes with the phosphates (Al, Fe, etc.) partially control glass dissolution in acidic media. Additional experiments carried out under saturated conditions — notably with respect to Si — in a solution enriched with phosphates showed that rare earth and Ca phosphates precipitated in the outer region of the alteration film, maintaining a glass dissolution rate significantly higher than in the control experiment. These observations have several implications. (1) Comparing the results obtained in the presence of phosphates and in the reference medium, the authors demonstrate deductively that glass dissolution is limited by the inner portion of the alteration film, i.e. the amorphous gel. (2) A kinetic law of SON 68 glass dissolution cannot be based on silica alone; the results of these experiments contradict Grambow’s model. (3) With regard to control of the glass dissolution kinetics by the protective properties of the gel, this type of experiment shows that the relation between the chemical composition and the microstructure of the gel is an important aspect in modeling the glass alteration kinetics, but that it is still poorly understood. 相似文献
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Keren Amram 《Geochimica et cosmochimica acta》2005,69(10):2535-2546
The main goal of this paper is to propose a new rate law describing the combined effect of pH (1 to 4.5) and temperature (25 to 70 °C) on smectite dissolution rate, under far from equilibrium conditions, as a step towards establishing the full rate law of smectite dissolution under acidic conditions. Dissolution experiments were carried out using non-stirred flow-through reactors fully immersed in a thermostatic water bath held at a constant temperature of 25.0°C, 50.0°C or 70.0°C ± 0.1°C. Smectite dissolution rates were obtained based on the release of silicon and aluminum at steady state. The results show good agreement between these two estimates of smectite dissolution rate. Low Al/Si ratios were obtained in experiments that were conducted at pH ≥4. These low Al/Si ratios are explained by precipitation of gibbsite and/or diaspore.Dissolution rate increases with temperature and decreases with increasing pH. Dissolution rates of experiments in which ΔGr ≤ −21 kcal mol −1, are not affected by deviation from equilibrium. Dissolution rates in most experiments are not affected by the addition of up to 0.3 M NaNO3 to the input solution.A simple model is used to describe the combined effect of pH and temperature on smectite dissolution rate. According to this model, dissolution rate is linearly proportional to the concentration of adsorbed protons on the mineral surface, and proton adsorption is described using a Langmuir adsorption isotherm. All experimental results at pH <4 were fitted to the model using a multiple non-linear regression. The resulting rate law is:
(A1) 相似文献
17.
The dissolution of Iceland spar in CO2-saturated solutions at 25°C and 1 atm total pressure has been followed by measurement of pH as a function of time. Surface concentrations of reactant and product species have been calculated from bulk fluid data using mass transport theory and a model that accounts for homogeneous reactions in the bulk fluid. The surface concentrations are found to be close to bulk solution values. This indicates that calcite dissolution under the experimental conditions is controlled by the kinetics of surface reaction. The rate of calcite dissolution follows an empirical second order relation with respect to calcium and hydrogen ion from near the initial condition (pH 3.91) to approximately pH 5.9. Beyond pH 5.9 the rate of surface reaction is greatly reduced and higher reaction orders are observed. Calculations show that the rate of calcite dissolution in natural environments may be influenced by both transport and surface-reaction processes. In the absence of inhibition, relatively short times should be sufficient to establish equilibrium. 相似文献
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Jonathan P. Icenhower B. Peter McGrail Eric M. Pierce David K. Shuh Jackie L. Steele 《Geochimica et cosmochimica acta》2008,72(12):2767-2788
The dissolution kinetics of five chemically complex and five chemically simple sodium silicate glass compositions (Na-Si±Al±B) were determined over a range of solution saturation values by varying the flow-through rates (1-100 mL/d) in a dynamic single-pass flow-through (SPFT) apparatus. The chemically complex borosilicate glasses are representative of prospective hosts for radioactive waste disposal and are characterized by relatively high molar Si/(Si + Al) and Na/(Al + B) ratios (>0.7 and >1.0, respectively). Analysis by X-ray absorption spectroscopy (XAS) indicates that the fraction of ivB to iiiB (N4) varies from 0.66 to 0.70. Despite large differences in bulk chemistry, values of δ29Si peak shift determined by MAS-NMR varies only by about 7 ppm (δ29Si = −94 to −87 ppm), indicating small differences in polymerization state for the glasses. Forward rates of reaction measured in dynamic experiments converge (average log10 rate [40 °C, pH 9] = −1.87 ± 0.79 [g/(m2 d)]) at high values of flow-rate (q) to sample surface area (S). Dissolution rates are independent of total Free Energy of Hydration (FEH) and this model appears to overestimate the impact of excess Na on chemical durability. For borosilicate glass compositions in which molar Na > Al + B, further addition of Na appears to stabilize the glass structure with respect to hydrolysis and dissolution. Compared to other borosilicate and aluminosilicate glasses, the glass specimens from this study dissolve at nearly the same rate (0-∼56×) as the more polymerized glasses, such as vitreous reedmergnerite (NaBSi3O8), albite, and silica. Dissolution of glass follows the order: boroaluminosilicate glass > vitreous reedmergnerite > vitreous albite > silica glass, which is roughly the same order of increasingly negative 29Si chemical shifts. The chemical shift of 29Si is a measure of the extent of bond overlap between Si and O and correlates with the forward rate of reaction. Thus, dissolution appears to be rate-limited by rupture of the Si-O bond, which is consistent with the tenants of Transition State Theory (TST). Therefore, dissolution at far from equilibrium conditions is dependent upon the speed of the rate-controlling elementary reaction and not on the sum of the free energies of hydration of the constituents of boroaluminosilicate glass. 相似文献
19.
ZHANG Xuetong ZHANG Ronghu HU Shumin YU WenbinOpen Research Laboratory of Geochemical Kinetics Chinese Academy of GeologicalSciences Baiwanzhuang Ro Beijing 《《地质学报》英文版》2000,74(2):406-411
This work presents new experimental results on surface chemistry of reacting minerals and interface kinetics between mineral and aqueous solutions. These experiments were carried out using a flow reactor (packed bed reactor) of an open system as well as a continuous stirred tank reactor, CSTR. The authors measured reaction rates of such minerals as zeolite, albite and carbonate (rhodochrosite, dolomite) in various solutions, and tested corresponding mineral surface by using SEM, XPS, SIMS, etc. This paper mainly presents the experimental results of zeolite dissolution in water and in low pH solutions at room temperature, and dolomite dissolution at elevated temperatures. The results show that the release rates of Si, Al and Na of zeolite are different in most cases. The incongruent dissolution of zeolite is related to surface chemical modifications. The Na, Al and Si release rates for dissolution of albite and zeolite in water and various solutions were measured as a function of temperature, flow veloci 相似文献
20.
R. Hellmann J.-M. Penisson R. L. Hervig J.-H. Thomassin M.-F. Abrioux 《Physics and Chemistry of Minerals》2003,30(4):192-197
Using an approach combining high-resolution and energy-filtered transmission electron microscopy (HRTEM and EFTEM), we have studied with Å to nm-spatial resolution the interfacial region that delimits the near-surface altered zone and non-altered labradorite feldspar after dissolution under acid pH conditions. The interface is characterized by extremely sharp and spatially coincident changes in structure and chemistry. The 500-nm-thick altered zone is depleted in interstitial cations (Ca, Na, K) and Al, a framework element, whereas it is enriched in H, O, and Si. Modeling H+-alkali interdiffusion within a 500-nm-thick altered zone shows that volume interdiffusion cannot reproduce the sharp chemical interfaces measured by EFTEM. Based on these new data, we propose that the near-surface altered zone is a result of interfacial dissolution-reprecipitation, and not of preferential leaching of cations and interdiffusion with H+. This implies an intrinsic dissolution process that is stoichiometric, where the breaking of bonds and release of interstitial cations and framework elements (Al, Si, and O) to solution occur contemporaneously at equal relative rates from the original fluid–mineral interface. 相似文献