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1.
According to the compositions of the underground gasfield brines in the west of Sichuan Basin,the phase equilibria in the ternary systems KBr-K2B4O7-H2O and KCl-K2B4O7-H2O at 373 K were studied using the isothermal dissolution equilibrium method.The solubilities of salts and the densities of saturated solutions in these ternary systems were determined.Using the experimental data,phase diagrams and density-composition diagrams were constructed.The two phase diagrams were simple co-saturation type,each having an invariant point,two univariant curves and two crystallization regions.The equilibrium solid phases in the ternary system KBr-K2B4O7-H2O are potassium bromide （KBr） and potassium tetraborate tetrahydrate （K2B4O7·4H2O）,and those in the ternary system KCl-K2B4O7-H2O are potassium chloride （KCl） and potassium tetraborate tetrahydrate （K2B4O7·4H2O）.Comparisons of the phase diagrams of the two systems at different temperatures show that there is no change in the crystallization phases,but there are changes in the size of the crystallization regions.As temperature increases,the solubility of K2B4O7·4H2O increases rapidly,so the crystallization field of K2B4O7·4H2O becomes smaller.  相似文献   

2.
正1 Introduction China has very abundant liquid mineral resources.Especially,the brine resources in the west of Sichuan Basin are pushed into the first place in China,whose K and B contents are unusually high.These rare liquid mineral resources have very good exploitation prospect(Lin,2001;2006).Generally speaking,phase equilibrium  相似文献   

3.
Two synthetic series of spinels, MgCr2O4–Fe2+Cr2O4 and MgCr2O4–MgFe2 3+O4 have been studied by Raman spectroscopy to investigate the effects of Fe2+ and Fe3+ on their structure. In the first case, where Fe2+ substitutes Mg within the tetrahedral site, there is a continuous and monotonic shift of the Raman modes A1g and Eg toward lower wavenumbers with the increase of the chromite component into the spinel, while the F2g modes remain nearly in the same position. In the second series, for low Mg-ferrite content, Fe3+ substitutes for Cr in the octahedral site; when the Mg-ferrite content nears 40 %, a drastic change in the Raman spectra occurs as Fe3+ starts entering the tetrahedral site as well, consequently pushing Mg to occupy the octahedral one. The Raman spectral region between 620 and 700 cm?1 is associated to the octahedral site, where three peaks are present and it is possible to observe the Cr–Fe3+ substitution and the effects of order–disorder in the tetrahedral site. The spectral range at 500–620 cm?1 region shows that there is a shift of modes toward lower values with the increase of the Mg-ferrite content. The peaks in the region at 200–500 cm?1, when observed, show little or negligible Raman shift.  相似文献   

4.
Experiments on water solubility in forsterite in the systems Mg2SiO4–K2Mg(CO3)2–H2O and Mg2SiO4–H2O–C were conducted at 7.5–14.0 GPa and 1200–1600 °C. The resulting crystals contain 448 to 1480 ppm water, which is 40–70% less than in the forsterite–water system under the same conditions. This can be attributed to lower water activity in the carbonate-bearing melt. The water content of forsterite was found to vary systematically with temperature and pressure. For instance, at 14 GPa in the system forsterite–carbonate–H2O the H2O content of forsterite drops from 1140 ppm at 1200 °C to 450 ppm at 1600 °C, and at 8 GPa it remains constant or increases from 550 to 870 ppm at 1300–1600 °C. Preliminary data for D-H-bearing forsterite are reported. Considerable differences were found between IR spectra of D-H- and H-bearing forsterite. The results suggest that CO2 can significantly affect the width of the olivine-wadsleyite transition, i.e., the 410-km seismic discontinuity, which is a function of the water content of olivine and wadsleyite.  相似文献   

5.
We define and calibrate a new model of molar volume as a function of pressure, temperature, ordering state, and composition for spinels in the supersystem (Mg, Fe2+)(Al, Cr, Fe3+)2O4 ? (Mg, Fe2+)2TiO4. We use 832 X-ray and neutron diffraction measurements performed on spinels at ambient and in situ high-P, T conditions to calibrate end-member equations of state and an excess volume model for this system. The effect on molar volume of cation ordering over the octahedral and tetrahedral sites is captured with linear dependence on Mg2+, Al3+, and Fe3+ site occupancy terms. We allow standard-state volumes and coefficients of thermal expansion of the end members to vary within their uncertainties during extraction of the mixing properties, in order to achieve the best fit. Published equations of state of the various spinel end members are analyzed to obtain optimal values of the bulk modulus and its pressure derivative, for each explicit end member. For any spinel composition in the supersystem, the model molar volume is obtained by adding excess volume and cation order-dependent terms to a linear combination of the five end-member volumes, estimated at pressure and temperature using the high-T Vinet equation of state. The preferred model has a total of 9 excess volume and order-dependent parameters and fits nearly all experiments to within 0.02 J/bar/mol, or better than 0.5 % in volume. The model is compared to the current MELTS spinel model with a demonstration of the impact of the model difference on the estimated spinel-garnet lherzolite transition pressure.  相似文献   

6.
The configurational heat capacity, shear modulus and shear viscosity of a series of Na2O–Fe2O3–Al2O3–SiO2 melts have been determined as a function of composition. A change in composition dependence of each of the physical properties is observed as Na2O/(Na2O + Al2O3) is decreased, and the peralkaline melts become peraluminous and a new charge-balanced Al-structure appears in the melts. Of special interest are the frequency dependent (1 mHz–1 Hz) measurements of the shear modulus. These forced oscillation measurements determine the lifetimes of Si–O bonds and Na–O bonds in the melt. The lifetime of the Al–O bonds could not, however, be resolved from the mechanical spectrum. Therefore, it appears that the lifetime of Al–O bonds in these melts is similar to that of Si–O bonds with the Al–O relaxation peak being subsumed by the Si–O relaxation peak. The appearance of a new Al-structure in the peraluminous melts also cannot be resolved from the mechanical spectra, although a change in elastic shear modulus is determined as a function of composition. The structural shear-relaxation time of some of these melts is not that which is predicted by the Maxwell equation, but up to 1.5 orders of magnitude faster. Although the configurational heat capacity, density and shear modulus of the melts show a change in trend as a function of composition at the boundary between peralkaline and peraluminous, the deviation in relaxation time from the Maxwell equation occurs in the peralkaline regime. The measured relaxation times for both the very peralkaline melts and the peraluminous melts are identical with the calculated Maxwell relaxation time. As the Maxwell equation was created to describe the timescale of flow of a mono-structure material, a deviation from the prediction would indicate that the structure of the melt is too complex to be described by this simple flow equation. One possibility is that Al-rich channels form and then disappear with decreasing Si/Al, and that the flow is dominated by the lifetime of Si–O bonds in the Al-poor peralkaline melts, and by the lifetime of Al–O bonds in the relatively Si-poor peralkaline and peraluminous melts with a complex flow mechanism occurring in the mid-compositions. This anomalous deviation from the calculated relaxation time appears to be independent of the change in structure expected to occur at the peralkaline/peraluminous boundary due to the lack of charge-balancing cations for the Al-tetrahedra.  相似文献   

7.
正1 Introduction The underground brine resources distributing widely in Sichuan Basin,China have drawn worldwide attention due to their unusual element abundance and excellent quality.  相似文献   

8.
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9.
The thermal stability of sideronatrite, ideally Na2Fe3+(SO4)2(OH)·3(H2O), and its decomposition products were investigated by combining thermogravimetric and differential thermal analysis, in situ high-temperature X-ray powder diffraction (HT-XRPD) and Fourier transform infrared spectroscopy (HT-FTIR). The data show that for increasing temperature there are four main dehydration/transformation steps in sideronatrite: (a) between 30 and 40 °C sideronatrite transforms into metasideronatrite after the loss of two water molecules; both XRD and FTIR suggest that this transformation occurs via minor adjustments in the building block. (b) between 120 and 300 °C metasideronatrite transforms into metasideronatrite II, a still poorly characterized phase with possible orthorhombic symmetry, consequently to the loss of an additional water molecule; X-ray diffraction data suggest that metasideronatrite disappears from the assemblage above 175 °C. (c) between 315 and 415 °C metasideronatrite II transforms into the anhydrous Na3Fe(SO4)3 compound. This step occurs via the loss of hydroxyl groups that involves the breakdown of the [Fe3+(SO4)2(OH)] ∞ 2? chains and the formation of an intermediate transient amorphous phase precursor of Na3Fe(SO4)3. (d) for T > 500 °C, the Na3Fe(SO4)3 compound is replaced by the Na-sulfate thenardite, Na2SO4, plus Fe-oxides, according to the Na3Fe3+(SO4)3 → 3/2 Na2(SO4) + 1/2 Fe2O3 + SOx reaction products. The Na–Fe sulfate disappears around 540 °C. For higher temperatures, the Na-sulfates decomposes and only hematite survives in the final product. The understanding of the thermal behavior of minerals such as sideronatrite and related sulfates is important both from an environmental point of view, due to the presence of these phases in evaporitic deposits, soils and sediments including extraterrestrial occurrences, and from the technological point of view, due to the use of these materials in many industrial applications.  相似文献   

10.
在１＊１０＾５Ｐａ,１４００℃条件下实验合成了不同成分的Ｎｉ（１－ｘ）ＺｎｘＦｅ２Ｏ４尖晶石,并将部分尖晶石在１１００℃和１６１０℃条件下重新平衡。采用粉晶Ｘ射线衍射法测定了尖晶石的晶胞参数。将实测的尖晶石晶胞参数与理论计算值进行对比,结果发现,在温度小于１４００℃时Ｎｉ（１－ｘ）ＺｎｘＦｅ２Ｏ４尖晶石中的四面体主要由Ｚｎ＾２＋、Ｆｅ＾３＋占据,而八面体主要由Ｎｉ＾２＋、Ｆｅ＾３＋占据,但至少当温  相似文献   

11.
The influence of Al–Cr substitution on the spinel structure was studied in synthetic single crystals belonging to the FeCr2O4–FeAl2O4 series produced by flux growth at 1,000–1,300 °C in controlled atmosphere. Samples were characterized by single-crystal X-ray diffraction, electron microprobe analyses and Mössbauer spectroscopy. Crystals of sufficient size and quality for single-crystal X-ray diffraction were obtained in the ranges Chr0–0.45 and Chr70–100 but not for intermediate compositions, possibly due to a reduced stability in this range. The increase in chromite component leads to an increase in the cell edge from 8.1534 (6) to 8.3672 (1) Å and a decrease in the u parameter from 0.2645 (2) to 0.2628 (1). Chemical analyses show that Fe2+ is very close to 1 apfu (0.994–1.007), Al is in the range 0.0793–1.981 apfu, Cr between 0 and 1.925 apfu. In some cases, Fe3+ is present in amounts up to 0.031 apfu. Spinels with intermediate Cr content (Chr component between 40 and 60) are strongly zoned with Cr-rich cores and Cr-poor rims. Mössbauer analyses on powdered spinels of the runs from which single crystal has been used for X-ray structural data show values of Fe3+/Fetot consistently larger than that calculated by EMPA on single crystals, presumably due to chemical variation between single crystals from the same runs. The synthesis runs ended at a temperature of 1,000 °C, but it is possible that cation ordering continued in the Cr-poor samples towards lower temperatures, possibly down to 700 °C.  相似文献   

12.
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13.
Several double salts have been detected in building materials and most of these salts are incongruently soluble compounds. In contrast to single salts, however, no systematic investigations of the crystallization behavior and deleterious effects of incongruently soluble double salts exist. To assess the damage potential of these salts, a systematic investigation of their highly complex behavior is desirable. This paper deals with the crystallization behavior of various solids in the ternary mixed NaNO3–Na2SO4 system including the formation of the double salt darapskite, Na3NO3SO4·H2O. The crystallization sequence during droplet evaporation experiments at room conditions was determined using Raman and polarization microscopy. The basic idea of this research is to use deviations of the crystallization sequence of a salt or a mixed salt solution from the equilibrium pathway as an indicator to detect the degree of supersaturation. The observed crystallization pathway includes the formation of the metastable phases Na2SO4(III), Na2SO4(V) and darapskite. The experimental observations are discussed on the basis of the NaNO3–Na2SO4–H2O phase diagram and the results provide evidence for crystal growth from highly supersaturated solutions in both systems. If the crystals growing under these conditions are confined, these supersaturations result in substantial crystallization pressures.  相似文献   

14.
The incorporation of hydrogen in enstatite in a hydrous system containing various amounts of NaCl was investigated at 25 kbar. The hydrogen content in enstatite shows a clear negative correlation to the NaCl-concentration in the system. The most favourable explanation is the reduction of water fugacity due to dilution. Other reasons for the limited hydrogen incorporation at high NaCl levels, such as a significant influence of Na+ on the defect chemistry or an exchange between OH- and Cl−in enstatite, appear much less important. A partition coefficient D Na En/Fluid = 0.0013 could be determined, demonstrating that Na is less incompatible in enstatite than H. The new results support the idea that dissolved components have to be considered when the total hydrogen storage capacity in nominally anhydrous minerals is estimated, especially in geological settings with high levels of halogens, such as subduction zones.  相似文献   

15.
Liquid–liquid immiscibility has crucial influences on geological processes, such as magma degassing and formation of ore deposits. Sulfate, as an important component, associates with many kinds of deposits. Two types of immiscibility, including (i) fluid–melt immiscibility between an aqueous solution and a sulfate melt, and (ii) fluid–fluid immiscibility between two aqueous fluids with different sulfate concentrations, have been identified for sulfate–water systems. In this study, we investigated the immiscibility behaviors of a sulfate- and quartz-saturated Na2SO4–SiO2–H2O system at elevated temperature, to explore the phase relationships involving both types of immiscibility. The fluid–melt immiscibility appeared first when the Na2SO4–SiO2–H2O sample was heated to ~270°C, and then fluid–fluid immiscibility emerged while the sample was further heated to ~450°C. At this stage, the coexistence of one water-saturated sulfate melt and two aqueous fluids with distinct sulfate concentrations was observed. The three immiscible phases remain stable over a wide pressure–temperature range, and the appearance temperature of the fluid–fluid immiscibility increases with the increased pressure. Considering that sulfate components occur extensively in carbonatite-related deposits, the fluid–fluid immiscibility can result in significant sulfate fractionation and provides implications for understanding the formation of carbonatite-related rare earth deposits.  相似文献   

16.
边为民 《矿物学报》1989,9(2):132-135
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17.
Li2B4O7—Na2B4O70H2O三元体系25℃相关系及物化性质实验   总被引：3，自引：0，他引：3  
通过实验研究了Ｌｉ２Ｂ４Ｏ７－Ｎａ２Ｂ４Ｏ７－Ｈ２Ｏ三元体系２５℃相关 溶液的物化性质，其２５℃相图由二条溶解度曲线构成，分别对应于Ｌｉ２Ｂ４Ｏ７．３Ｈ２Ｏ、Ｎａ２Ｂ４Ｏ７．１０Ｈ２Ｏ相区，属简单共饱和型。简要讨论了该体系硼酸盐在水听溶解行为，并用经验公式描述了物有浓度的变化规律。  相似文献   

18.
Two synthetic single-crystals with composition Li(Al0.53Ga0.47)Si2O6 and LiGaSi2O6 and space group C2/c at room conditions have been studied under pressure by means of X-ray diffraction using a diamond anvil cell. The unit-cell parameters were determined at 12 and 10 different pressures up to P = 8.849 and P = 7.320 GPa for Li(Al0.53Ga0.47)Si2O6 and LiGaSi2O6, respectively. The sample with mixed composition shows a C2/c to P21/c phase transformation between 1.814 and 2.156 GPa, first-order in character. The transition is characterised by a large and discontinuous decrease in the unit-cell volume and by the appearance of the b-type reflections (h + k = odd) typical of the primitive symmetry. The Ga end-member shows the same C2/c to P21/c transformation at a pressure between 0.0001 and 0.39 GPa. The low-pressure value at which the transition occurred did not allow collecting any data in the C2/c pressure stability field except that on room pressure. Our results compared with those relative to spodumene (LiAlSi2O6, Arlt and Angel 2000a) indicate that the substitution of Al for Ga at the M1 site of Li-clinopyroxenes strongly affects the transition pressure causing a decrease from 3.17 GPa (spodumene) to less than 0.39 GPa (LiGaSi2O6) and decreases the volume discontinuity at the transition. As already found for other compounds, the C2/c low-pressure phases are more rigid than the P21 /c high-pressure ones. Moreover, the increase of the M1 cation radius causes a decrease in the bulk modulus K T0. The axial compressibility among the Li-bearing clinopyroxenes indicates that the c axis is the most rigid for the C2/c phases while it becomes the most compressible for the P21 /c phases.  相似文献   

19.
The polymorphic relations for Mg3(PO4)2 and Mg2PO4OH have been determined by reversed experiments in the temperature-pressure (T-P) range 500–1100 °C, 2–30 kbar. The phase transition between the low-pressure phase farringtonite and Mg3(PO4)2-II, the Mg analogue of sarcopside, is very pressure dependent and was tightly bracketed between 625 °C, 7 kbar and 850 °C, 9 kbar. The high-temperature, high-pressure polymorph, Mg3(PO4)2-III, is stable above 1050 °C at 10 kbar and above 900 °C at 30 kbar. The low-pressure stability of farringtonite is in keeping with its occurrence in meteorites. The presence of iron stabilizes the sarcopside-type phase towards lower P. From the five Mg2PO4OH polymorphs only althausite, holtedahlite, β-Mg2PO4OH (the hydroxyl analogue of wagnerite) and ɛ-Mg2PO4OH were encountered. Relatively speaking, holtedahlite is the low-temperature phase (<600 °C), ɛ-Mg2PO4OH the high-temperature, low-pressure phase and β-Mg2PO4OH the high-temperature, high-pressure phase, with an intervening stability field for althausite which extends from about 3 kbar at 500 °C to about 12 kbar at 800 °C. Althausite and holtedahlite are to be expected in F-free natural systems under most geological conditions; however, wagnerite is the most common Mg-phosphate mineral, implying that fluorine has a major effect in stabilizing the wagnerite structure. Coexisting althausite and holtedahlite from Modum, S. Norway, show that minor fluorine is strongly partitioned into althausite (KD F/OH≈ 4) and that holtedahlite may incorporate up to 4 wt% SiO2. Synthetic phosphoellenbergerite has a composition close to (Mg0.9□0.1)2Mg12P8O38H8.4. It is a high-pressure phase, which breaks down to Mg2PO4OH + Mg3(PO4)2 + H2O below 8.5 kbar at 650 °C, 22.5 kbar at 900 °C and 30 kbar at 975 °C. The stability field of the phosphate end-member of the ellenbergerite series extends therefore to much lower P and higher T than that of the silicate end-members (stable above 27 kbar and below ca. 725 °C). Thus the Si/P ratio of intermediate members of the series has a great barometric potential, especially in the Si-buffering assemblage with clinochlore + talc + kyanite + rutile + H2O. Application to zoned ellenbergerite crystals included in the Dora-Maira pyrope megablasts, western Alps, reveals that growth zoning is preserved at T as high as 700–725 °C. However, the record of attainment of the highest T and/or of decreasing P through P-rich rims (1 to 2 Si pfu) is only possible in the presence of an additional phosphate phase (OH-bearing or even OH-dominant wagnerite in these rocks), otherwise the trace amounts of P in the system remain sequestered in the core of Si-rich crystals (5 to 8 Si pfu) and can no longer react. Received: 7 April 1995 / Accepted: 12 November 1997  相似文献   

20.
The behaviour of two types of limestones having a different porosity, Maastricht and Euville limestone, laden with aqueous solutions of equimolar mixtures of sodium sulphate/sodium nitrate or sodium sulphate/potassium sulphate was investigated. At 50 % RH, the efflorescences on Maastricht samples during the first 30 h of drying consisted of similar amounts of thenardite and darapskite in case of an equimolar mixture of sodium sulphate/sodium nitrate while those on Euville samples under the same conditions contained mainly darapskite. After drying at 20 °C and 85 % RH, thenardite, formed through the precipitation and dehydration of mirabilite, was mostly detected in the efflorescences on both Maastricht and Euville samples. Re-wetting by increasing the RH from 50 to 85 % resulted in substantial damage on Maastricht stone laden with an equimolar mixture of sodium sulphate/sodium nitrate as a consequence of high supersaturation of mirabilite. In case of a contamination with equimolar amounts of sodium sulphate and potassium sulphate, the efflorescence on both limestones during drying at 50 % RH contained predominantly aphthitalite. The observed crystallisation behaviour is compared to the theoretical behaviour. The results indicate a strong influence of stone properties on the crystallisation behaviour of salt mixtures.  相似文献   

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