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1.
《Tectonophysics》2004,378(3-4):141-142
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2.
A simple theoretical model of magnetic–hydrophobic coagulation considering the total interaction potential energy between two spheres exposed to an external magnetic field as a sum of the van der Waals, electrostatic, magnetic, and hydrophobic components is proposed. The model was used to interpret experiments on coagulation of fine siderite particles in distilled water and 10−2 M KCl, hydrophobized by sodium oleate. In the experiments, a relative extent of the coagulation/stability equilibrium of the siderite suspension was evaluated photoelectrically. To estimate the model parameters, the ζ-potential and hydrophobicity of siderite particles were measured.A qualitative agreement was obtained between the model predictions (energy maximum and secondary minimum) and the experimental results (voltage changes after a selected interval of sedimentation) of the siderite suspensions. Moreover, a statistically significant correlation was found between the experimental voltages and the calculated energy maximum (a crucial factor of theories on the fine particle coagulation kinetics), which can be represented by a linear regression equation with the correlation coefficient of 0.979.  相似文献   

3.
The main objective of this paper is to examine how different engineering soils react to environmental variations and to provide correlations to characterize their behaviour under null external mechanical stress. Two French and two Algerian soils with liquid limits ranging from 36 to 112 were prepared under both slurry and Proctor compaction conditions, and then subjected to drying–wetting paths with suction controlled from several kPa to several hundreds of MPa. Experimental results are presented in five diagrams to show globally and simultaneously the shrinkage–swelling, saturation–desaturation and water retention characteristics. A reasonable consistency was observed between the oedometric and drying curves of slurry, confirming the equivalence between hydraulic loading (suction) and mechanical loading (consolidation stress) on the volume change behaviour of different soils. As an intrinsic parameter of soil nature, liquid limit was found to have a significant influence on the shrinkage limit, air-entry suction and compressibility of both slurry and compacted samples. For that reason, correlations between these characteristics and liquid limit were set up, providing a good basis for a first estimation of the drying–wetting curves. At the micro-scale, new experimental results were obtained: either on drying or wetting path, the micro-pores were almost unaffected, whereas, when matrix suction increased from 0.1 to 8 MPa, the volume of macro-pores decreased to quasi-closure. At last, the analogy between the compaction and drying–wetting curves, and the comparison of different methods to determine the water retention curve were addressed. Such analogies and comparisons contribute to a better understanding of the mechanisms of mechanical stress and suction.  相似文献   

4.
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5.
Gail Davies 《Geoforum》2010,41(5):667-670
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6.
The crystallization sequence of a basaltic andesite from Bezymianny Volcano, Kamchatka, Russia, was simulated experimentally at 100 and 700 MPa at various water activities (aH2O) to investigate the compositional evolution of residual liquids. The temperature (T) range of the experiments was 950–1,150 °C, aH2O varied between 0.1 and 1, and the log of oxygen fugacity (fO2) varied between quartz–fayalite–magnetite (QFM) and QFM + 4.1. The comparison of the experimentally produced liquids and natural samples was used to constrain the pressure (P)–T–aH2O–fO2 conditions of the Bezymianny parental magma in the intra-crustal magma plumbing system. The phase equilibria constraints suggest that parental basaltic andesite magmas should contain ~2–2.5 wt% H2O; they can be stored in upper crustal levels at a depth of ~15 km, and at this depth they start to crystallize at ~1,110 °C. The subsequent chemical evolution of this parental magma most probably proceeded as decompressional crystallization occurred during magma ascent. The final depths at which crystallization products accumulated prior to eruption are not well constrained experimentally but should not be shallower than 3–4 km because amphibole is present in natural magmas (>150 MPa). Thus, the major volume of Bezymianny andesites was produced in a mid-crustal magma chamber as a result of decompressional crystallization of parental basaltic andesites, accompanied by mixing with silicic products from the earlier stages of magma fractionation. In addition, these processes are complicated by the release of volatiles due to magma degassing, which occurs at various stages during magma ascent.  相似文献   

7.
To explore the effect of bulk composition on the solidus of carbonated eclogite, we determined near-solidus phase relations at 3 GPa for four different nominally anhydrous, carbonated eclogites. Starting materials (SLEC1, SLEC2, SLEC3, and SLEC4) were prepared by adding variable proportions and compositions of carbonate to a natural eclogite xenolith (66039B) from Salt Lake crater, Hawaii. Near-solidus partial melts for all bulk compositions are Fe–Na calcio-dolomitic and coexist with garnet + clinopyroxene + ilmenite ± calcio-dolomitic solid solution. The solidus for SLEC1 (Ca#=100 × molar Ca/(Ca + Mg + FeT)=32, 1.63 wt% Na2O, and 5 wt% CO2) is bracketed between 1,050°C and 1,075°C (Dasgupta et al. in Earth Planet Sci Lett 227:73–85, 2004), whereas initial melting for SLEC3 (Ca# 41, 1.4 wt% Na2O, and 4.4 wt% CO2) is between 1,175°C and 1,200°C. The solidus for SLEC2 (Ca# 33, 1.75 wt% Na2O, and 15 wt% CO2) is estimated to be near 1,100°C and the solidus for SLEC3 (Ca# 37, 1.47 wt% Na2O, and 2.2 wt% CO2) is between 1,100°C and 1,125°C. Solidus temperatures increase with increasing Ca# of the bulk, owing to the strong influence of the calcite–magnesite binary solidus-minimum on the solidus of carbonate bearing eclogite. Bulk compositions that produce near-solidus crystalline carbonate closer in composition to the minimum along the CaCO3-MgCO3 join have lower solidus temperatures. Variations in total CO2 have significant effect on the solidus if CO2 is added as CaCO3, but not if CO2 is added as a complex mixture that maintains the cationic ratios of the bulk-rock. Thus, as partial melting experiments necessarily have more CO2 than that likely to be found in natural carbonated eclogites, care must be taken to assure that the compositional shifts associated with excess CO2 do not unduly influence melting behavior. Near-solidus dolomite and calcite solid solutions have higher Ca/(Ca + Mg) than bulk eclogite compositions, owing to Ca–Mg exchange equilibrium between carbonates and silicates. Carbonates in natural mantle eclogite, which have low bulk CO2 concentration, will have Ca/Mg buffered by reactions with silicates. Consequently, experiments with high bulk CO2 may not mimic natural carbonated eclogite phase equilibria unless care is taken to ensure that CO2 enrichment does not result in inappropriate equilibrium carbonate compositions. Compositions of eclogite-derived carbonate melt span the range of natural carbonatites from oceanic and continental settings. Ca#s of carbonatitic partial melts of eclogite vary significantly and overlap those of partial melts of carbonated lherzolite, however, for a constant Ca-content, Mg# of carbonatites derived from eclogitic sources are likely to be lower than the Mg# of those generated from peridotite.  相似文献   

8.
In this study, we address volume diffusion of ytterbium in yttrium aluminum garnet (YAG) using thin-film single crystal diffusion couples. We employ analytical transmission electron microscopy (ATEM) as a tool for combined microstructural and microchemical analysis and compare the results to Rutherford backscattering (RBS) analysis. Given the high spatial resolution of the method, we focus on microstructural changes of the thin-film diffusant source during the diffusion anneal. We evaluate the potential influence of the associated changes in its transport properties on the evolution of concentration profiles in the single crystal substrate. This approach allows us to test the reliability of determination of volume diffusion coefficients from thin-film diffusion experiments. We found that for the chosen experimental setting, the influence of thin-film re-crystallization is small when compared with the experimental uncertainty and good estimates for the volume diffusion coefficients of Yb in YAG can be obtained using standard assumptions. Both Yb-concentration profiles analyzed with ATEM and with RBS give similar results. At 1,450°C and 1 bar, we infer log D Yb (m2/s) values of −19.37 ± 0.07 (TEM) and −19.84 ± 0.02 (RBS). Although the change in thin-film transport properties associated with successive crystallization during the diffusion anneal does not play a major role for our experimental setup, this effect cannot generally be ignored.  相似文献   

9.
Here, we present the first analytical technique (the quartz tube system technique—QTS) to directly analyze H2O and CO2 contents in liquids following high-pressure, high-temperature experiments in capsules containing mantle minerals and a diamond layer serving as a fluid/melt trap. In this technique, the capsule is frozen prior to opening; the diamond trap is cut out of the capsule and placed inside a N2-filled quartz tube. The diamond trap is heated up to 900 °C to release the gases to an Infrared Gas Analyzer, which determines the CO2 and H2O contents. Three sets of experiments containing SiO2 and CaCO3 powders were performed at 6 GPa and 1,000 °C in order to calibrate and validate the technique. These experiments demonstrated that when samples are prepared in a N2 environment, CO2 and H2O can be directly measured with an accuracy and precision of 2–3 and 3–4 %, respectively. The QTS technique (for H2O and CO2 determination) together with the cryogenic technique (total dissolved solids content) can be applied to diamond-trap capsules following HP–HT experiments in order to provide direct and complete liquid compositions coexisting with mantle material. The principal advantage of the QTS technique of direct analysis of volatile content in liquids over the indirect approach of mass balance calculations is the possibility of studying carbonated and hydrous liquid compositions in equilibrium with mantle material regardless of chemistry and pressure–temperature experimental conditions.  相似文献   

10.
The aim of this study is to improve our knowledge of the processes that lead to clay smear during faulting of a layered sand-clay sequence in an analogue sandbox model. We carefully characterized mechanical properties of the materials used by a series of geotechnical tests. Displacement field was quantified using PIV (Particle Image Velocimetry). The model is water-saturated to allow the deformation of wet clay and sand in one experiment comprising a sand package with a horizontal layer of clay above a predefined rigid basement fault. The thickness and rigidity of the clay layer are the parameters varied in this study. The model shows a range of structures that are related to competence contrast between sand and different clay types. Results show ductile shearing of soft clay with a transition to brittle fracturing of stiff clay accompanied by the formation of rotating clay blocks in the fault zone. Localized deformation is observed through time showing (i) the propagation of one active fault migrating laterally through the sediment package, and (ii) the formation of a stable prism between two or more active faults that gets progressively smaller with minor rotation of the hanging wall fault. Continuous clay smear is observed resulting from the lateral injection of clay as well as from a reworked mixture of sand and clay.  相似文献   

11.
To understand the fundamental chemical processes of fluid–rock interaction during the pulverization of quartz grains in fault zones, quartz grains were crushed within pure water. The crushing experiments were performed batch style using a shaking apparatus. The crushing process induced a decrease in pH and an increase in hydrogen gas with increased shaking duration. The amount of hydrogen ions generated was five times larger than that of the hydrogen gas, which was consistent with the amount of Si radicals estimated from electron spin resonance measurements by Hochstrasser and Antonini (1972). This indicates that hydrogen gas was generated by consuming most of the Si radicals. The generation of hydrogen ions was most likely related to the presence of silanols on the newly formed mineral surface, implying a change of proton activities in the fluid after pulverization of quartz.  相似文献   

12.
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13.
Acta Geotechnica - This paper presents an experimental and analytical/numerical study of the mechanics of cemented granular materials (CGMs). This study incorporates both in situ X-ray tomography...  相似文献   

14.
 Retardation parameters (Rf) for sulfolane and thioalne were estimated using reference values and experimentally as they were mainly observed at an aquifer underneath a waste disposal site near Brisbane, Australia. Three soil aquifer materials e.g. clay, silty clay and sand were used as sorbents. At first, Rf was obtained employing Koc–Kow and solubility parameter, respectively, while experimental coefficients were determined from both batch and flow-through column tests. Additionally, Rf was observed at a single- and bi-solute system through the column test. There was not found any significant difference in Rf between Koc–Kow and solubility parameters, but the retardation coefficient was significantly dependent on organic carbon content for solubility parameter. In contrast, using Koc–Kow, the coefficient correspondingly varied with an amount of clay content contained in each soil. In the same manner, the batch-determined parameters were more subject to clay content. On the other hand, the column-determined parameters can be comparable with the desk-derived values. In a bi-solute system, they did not influence each other concerning retardation coefficients while they flew though the column simultaneously. It was concluded that there was a large discrepancy in retardation coefficient of batch- against both reference-oriented estimation and column-determined values. Received: 20 August 1998 · Accepted: 17 May 1999  相似文献   

15.
《Organic Geochemistry》2011,42(12):1489-1501
Mineral–organic associations act as mediators of litter-derived N flow to the mineral soil, but the time scales and pathways involved are not well known. To close that gap, we took advantage of decade old 15N litter labeling experiments conducted in two European forests. We fractionated surface soils by density with limited disaggregating treatment and investigated organic matter (OM) characteristics using δ13C, δ15N and the C/N ratio. Mineral properties were studied by X-ray diffraction and selective dissolution of pedogenic oxides.Three types of associations were isolated: plant debris with few trapped minerals (<1.65 g/cm3), aggregates dominated by phyllosilicates (1.65–2.4 g/cm3), and single mineral grains and pedogenic oxides with little OM (>2.4 g/cm3). A small proportion of 15N tracer was rapidly attached to single mineral grains, while most of it moved from plant debris to aggregates of low density and progressively to aggregates of higher density that contain a more microbially processed OM. After a decade, 60% of the 15N tracer found in the investigated horizon was retained in aggregates, while plant debris still contained 40% of the tracer.We present a conceptual model of OM and N flow through soil mineral–organic associations, which accounts for changes in density, dynamics and chemistry of the isolated structures. It suggests that microbial reworking of OM entrapped within aggregates (1.65–2.4 g/cm3) causes the gradient of aggregate packing and, further on, controls the flow of litter-derived N through aggregates. For associations with denser material (>2.4 g/cm3), mineralogy determines the density of the association, the type of patchy OM attached to mineral surfaces and controls the extent of litter-derived N incorporation.  相似文献   

16.
Square sections of a Mn-rich slag from an alkaline battery recycling plant were submitted to 6-month batch leaching procedures. High-Purity Water (HPW), acidic (pH 4) and alkaline (pH 12) conditions were used in order to observe the behavior of primary solid phases as well as the constituent elements (Mn, Mg, Al, Si, Ca). The experiments were coupled with both KINDIS(P) modeling and mineralogical study (SEM-EDS). Experimental results showed that the Mn-rich slag was sensitive to acidic conditions which induced the dissolution of primary phases. Moreover, pH 4 conditions did not result in the formation of newly formed solid products, leading to the greatest mobilization of metallic elements (especially Mn). Alkaline conditions favored the precipitation of secondary phases, especially rhodochrosite, calcite and Mg-saponite, inducing low mobilization of the contained elements. The KINDIS(P) modeling allowed the stability of primary phases and newly formed products to be predicted. Although the modeled results have to be considered with caution, they allow the assessment and understanding of future environmental behavior of the solid material in given conditions. In this case, the reuse of Mn-rich slag in acidic conditions has to be avoided because of the acidic dissolution of the primary phases.  相似文献   

17.
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18.
Torsion experiments were performed on synthetic aggregates of calcite with a 50% volume of muscovite. The tests were performed at 627–727 °C with a confining pressure of 300 MPa at constant shear strain rates of 3 × 10?5–3 × 10?4 s?1 on cylindrical samples with the starting foliation parallel and perpendicular to the cylinder axis. Both the foliation parallel and the foliation perpendicular experiments show similar stress–strain patterns, with an initial hardening stage followed by significant strain weakening (>60%) before a catastrophic rupture. Microstructural analysis shows that in low-strain experiments calcite grains are intensely twinned while muscovite grains appear slightly bent and kinked. Higher strains promote a segregation of the two phases with calcite forming thin layers of fine, dynamically recrystallized grains, which act as localized shear bands, while muscovite grains keep their original size and rotate assuming a strong shape preferred orientation. This strain localization of the calcite from an initially homogeneous rock produced catastrophic failure at moderate bulk shear strains (γ ～ 3). Localization of the strain first involved ductile deformation to produce a new calcite layering with fine dynamically recrystallized grains along which cavities nucleated. The orientation and kinematics of the cavities are comparable to R1 Riedel structures. All experiments on calcite–muscovite mixtures resulted in heterogeneous strain. In these torsion experiments chemical changes and crystallization of new phases (anorthite and kalsilite) are observed at 627 °C. Whereas, samples hot pressed or deformed in compression at 670 °C did not show such reactions or any localization. The effect of stress-field geometry and pore pressure upon mineral reactions is discussed. It is concluded that deformation-induced heterogeneous phase distributions caused local strength differences initiating strain localization in the calcite–muscovite mixtures, eventually leading to plastic failure.  相似文献   

19.
《Applied Geochemistry》2003,18(9):1361-1371
The study of inactive As-bearing tailings impoundments at the Khovu-Aksy mine-site (Russia) revealed high concentrations of As in the porewater of tailings solids and in their aqueous extracts, as well as in adjacent soils. In these investigations, experimental leaching of As-containing tailings was performed in the laboratory. The three types of solutions which were used in the leach experiments to model natural waters and waters of anthropogenic origin were H2O, HNO3 and NH4HCO3, and during leaching with these solutions As concentrations were maintained at 10±2, 16±1 and ∼20 mg/l. No low-pH waters were observed at the end of the leach experiments, where pH varied between 8.3 and 9.1. These alkaline pH conditions are attributed to the effect of acid consuming carbonate mineral dissolution reactions, which are also indicated by increased concentrations of Mg and Ca. Also, the solution of certain heavy metals (Co, Ni, Fe) was negligible compared to that of As, and these metals were assumed to have been conserved in the solid phase. Analysis of the leach solutions, and modeling of the results showed that As could be removed from the surface of different particles where it had been adsorbed, and also its concentration could increase with time from the breakdown of Ca(Mg)- and Ni(Co)-arsenate phases. In the absence of an effective remediation program, As release will continue to be an environmental problem.  相似文献   

20.
Boom Clay is currently viewed as a reference host formation for studies on deep geological disposal of radioactive waste in Belgium. The interactions between bulk rock Boom Clay and 0.1 M KOH, 0.1 M NaOH, 0.1 M Ca(OH)2, young cement water and evolved cement water solutions, ranging in pH from 12.5 to 13.2, were examined as static batch experiments at 60 °C to simulate alkaline plume perturbations, which are expected to occur in the repository due to the presence of concrete. Both liquids and solids were investigated at specific times between 90 and 510 days in order to control the elemental budget and to search for potential mineralogical alterations. Also, the clay fraction was separated from the whole-rock Boom Clay at the end of each run and characterized for its mineralogical composition. Thereby, the importance of the mineral matrix to buffer the alkaline attack and the role of organic matter to protect clay minerals were also addressed. The results indicate that the degree of geochemical perturbation in Boom Clay is dependent on the initial pH of the applied solution together with the nature of the major cation in the reactant fluids. The higher the initial pH of the media, the stronger its interaction with Boom Clay. No major non-clay mineralogical alteration of the Boom Clay was detected, but dissolution of kaolinite, smectite and illite occurred within the studied experimental conditions. The dissolution of clays is accompanied by the decrease in the layer charge, followed by a decrease in the cation-exchange capacity. The highest TOC values coincide with the highest total elemental concentrations in the leachates, and correspondingly, the highest dissolution degree. However, no quantitative link could be established between the degree of organic matter decomposition and clay dissolution.  相似文献   

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