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1.
电气石岩——一种和矿化有关的岩石类型 总被引：7，自引：2，他引：7
电气石是一种复杂的含水、氟、氯硅酸盐矿物族,其一般分子式为WX_3Y_6(BO_3)_3Si_3O_(18)(OH,F,Cl),其中W=Na~+、Ca~(2+)、K~+,X=Al~(3+)、Fe~(3+)、Fe~(2+)、Li~+、Mg~(2+)、Mn~(2+),Y=Al~(3+)、Fe~(3+)、Cr~(3+)、V~(3+)。该矿物族存在许多端员矿物,如黑电气石、镁电气石和钙镁电气石等。电气石在很大范围的温压条件下稳定,故其可提供有关岩浆或流体的一些信息,如P、T、fo_2、α_(H_2O)、α_(F)~-、Mg/(Mg+Fe)比值等(Plimer,1988);同时该矿物类质同象替换十分复杂,其常量元素组成可提供其形成的地质体系化学组成的线索,Henry和Guidotti(1985)在Al-∑Fe-Mg和Ca-∑Fe-Mg三角图解上确定了不同类型岩石中电气石的特定区域。电 相似文献
2.
深地质处置目前被国际上公认为是处置高放废物的最有效可行的方法。我国采用多重工程屏障系统和适宜的地质体共同作用来确保与生物圈的安全隔离。缓冲材料是高放废物重要的工程屏障材料之一,我国选用高庙子钠基膨润土作为缓冲材料的基础材料。膨润土作为缓冲材料的一个重要性能表现为缓冲孔隙水的化学变化。介绍了GMZ-1钠基膨润土大气条件下与蒸馏水的反应试验,并对试验结果进行了讨论。批式试验反应溶液中钠离子来源于钠基膨润土层间阳离子和矿物溶解,镁离子来源于钠基膨润土层间阳离子,钾离子和钙离子来源于矿物溶解,相关研究认识对于高放废物处置库近场核素迁移研究和评价工程屏障的长期稳定性具有重要意义。 相似文献
3.
海绿石是一种浅海相沉积指示矿物,形成成熟的海绿石需1Ma。本文以含铁量很低的蒙脱石和0.1mol/LFe~(3+)、0.2mol/LK~+的离子溶液分别为初始物质在50℃恒温环境和不同的pH、Eh条件下,模拟海绿石化过程,并通过XRD、FTIR、SEM、ESR等检测反应产物。研究发现,在SEM下观察到球形纳米颗粒的海绿石出现;同时XRD谱图上除出现云母类矿物的001衍射峰外,还出现d值为0.1520nm和0.1498nm的代表海绿石和铁伊利石的060特征衍射峰。pH和氧化还原条件对产物的影响比较显著,pH为酸性时出现海绿石和铁伊利石的组合,其红外吸收谱中出现AlFe~(2+)OH或Mg~(2+)Fe~(3+)OH(3547~3562cm~(-1))、Fe~(3+)Fe~(3+)OH的伸缩振动峰,与之相应的ESR中出现g=1.978的八面体位Fe~(3+)的共振峰;当pH介于中性的时候,红外光谱谱图上出现明显的AlFe~(2+)OH、Mg~(2+)Fe~(3+)OH(3550~3562cm~(-1))和Al~(3+)Fe~(3+)OH(870cm~(-1))振动;pH为碱性时,出现Fe~(3+)Mg~(2+)OH(3560cm~(-1))振动;上述红外吸收振动的出现表明Fe~(3+)已经进入了蒙脱石结构的八面体位。蒙脱石在上述条件下发生明显的改变,发生海绿石化或铁伊利石化,pH和氧化还原条件对结果的影响比较显著,酸性的环境中海绿石化显著,而中性至碱性的环境则发生铁伊利石化。 相似文献
4.
5.
在磷酸介质中对铀的还原反应,铁粉比亚铁离子具有更高的还原能力。 Fe~2+2e=Fe,E~0=-0.409伏。当H_3PO_4浓度达7.090M时, Fe~3+e=Fe~(2+),E~0=0.448伏, 此时的 UO~(2+)_2+4H~++2e=U~(4+)+2H_2O,E~0=0.595伏。根据氧化-还原电位次序,在磷酸介质中铁粉和亚铁都能还原铀(Ⅵ),但铁粉还原能力强,且生成的亚铁又可以还原铀(Ⅵ),一个F~o_c相当于3个Fe~(2+)的电子失掉的还原剂作用。经研究实验铁粉用量为0.02—0.03克,比用亚铁还原法的莫尔盐中亚铁量0.048— 相似文献
6.
中国高放废物深地质处置的缓冲材料选择及其基本性能 总被引：12，自引：0，他引：12
人类的许多生产、生活活动均可能产生不同活度的放射性废物,其中高放废物的安全处置倍受全球科学家和广大公众所重视。目前深地质处置被国际上公认为处置高放废物的最有效可行的方法。借鉴国外成熟的技术和经验,我国采用多重工程屏障系统(包括废物固化体、废物容器及其外包装和缓冲/回填材料)和适宜的围岩地质体共同作用,来确保高放废物与生物圈的安全隔离。膨润土由于具有极低的渗透性和优良的核素吸附等性能而被国际上选作缓冲材料的基础材料。经过全国膨润土矿床筛选,我国高放废物深地质处置库缓冲材料的研究以产自高庙子膨润土矿床深部的钠基膨润土作为基本组成材料。本文介绍了高庙子膨润土矿床的地质特征以及高庙子钠基膨润土的基本特征。该膨润土与国外同类型材料相比具有蒙脱石含量高(75%左右)、杂质矿物相对较少的特点,该材料的系统和深入研究对于开发我国缓冲回填材料技术、确保高放废物的安全有效处置有重要意义。 相似文献
7.
《矿物岩石地球化学通报》2016,(2)
蛇纹石化橄榄岩是温都尔庙蛇绿岩套中最为重要的岩石类型,主要矿物组合为蛇纹石+碳酸盐矿物+磁铁矿+滑石。富SiO_2流体的加入,促使岩石进一步发生蛇纹石化作用而缺失水镁石。穆斯堡尔谱测量揭示了铁元素化学种的分布特征,蛇纹石化程度与氧化-还原特征的相关性。蛇纹石化橄榄岩含铁总量和Fe~(3+)的分布与磁铁矿和蛇纹石密切相关,Fe~(3+)以分布于蛇纹石中占优势。这对正确估算蛇纹石化过程中H_2的生成量有十分重要的意义,对估算俯冲带Fe~(3+)输入和评估原生地幔岩的蛇纹石化作用有重要参考价值。 相似文献
8.
通过单矿物浮选、溶液化学计算、Zeta电位测试以及红外光谱分析等手段研究了金属阳离子(Fe~(3+)、Zn~(2+)、Fe~(2+)和Pb~(2+))对重晶石浮选行为的影响以及作用原理。浮选结果表明,在十二烷基磺酸体系下,4种金属阳离子Fe~(3+)、Zn~(2+)、Fe~(2+)和Pb~(2+)在p H值为4.0～11.2范围内对重晶石的可浮性都具有活化作用,其中Pb~(2+)对重晶石的可浮性活化效果最好,Fe~(2+)次之。Pb~(2+)活化机理研究显示,Pb~(2+)主要以Pb~(2+)、Pb(OH)~+的形式和重晶石表面吸附的OH~-结合并脱水,然后吸附在重晶石矿物表面并促进十二烷基磺酸根阴离子在重晶石表面的吸附,从而增强了重晶石的可浮性。 相似文献
9.
10.
中国高放废物地质处置缓冲材料大型试验台架和热-水-力-化学耦合性能研究 总被引：1，自引：0，他引：1
缓冲材料作为高放废物深地质处置库中一道重要的人工屏障,与高放废物容器和处置库围岩直接接触,在高放废物衰变热、辐射作用和地下水等影响下产生复杂的热-水-力-化学耦合作用,为了验证缓冲材料是否能长期有效地发挥其屏障材料的作用,核工业北京地质研究院利用高庙子钠基膨润土组装并运行了模拟中国高放废物地质处置室 尺寸的大型缓冲材料膨润土试验台架（China-Mock-Up）。建立了缓冲材料试验台架的安装和试验方法,依据实测数据和理论分析,揭示了热-水-力-化学耦合作用条件下膨润土中的相对湿度是在加热器的热效应和外部供水的湿效应共同作用下发生变化的,压实膨润土中应力的变化主要是由于膨润土遇水膨胀和加热器的热效应引起的,试验验证了模拟高放废物地质处置室内加热器（废物罐）运行初期的位移过程,为缓冲材料和高放废物地质处置库的设计提供了重要的工程参数和理论依据。 相似文献
11.
In order to determine whether Li+ cations penetrate into the octahedral layers of montmorillonites upon mild heating (Hofmann-Klemen effect) 57Fe Mössbauer spectra of Na+ and Li+ exchanged montmorillonite were obtained before and after treatment at 220 ° C. The 57Fe nucleus was used as a remote probe to detect electronic perturbations which would occur if a Li cation was to move into the octahedral layer from the interlayer after heating. The ambient Mössbauer spectra showed that a high charge density interlayer cation such as Li+ is effective in reducing the phonon energy of VIFe2+. In addition the EFG at octahedral sites can be significantly modified by interlayer cations as evidenced by the larger quadrupole splitting value measured for the Li+-exchanged sample with respect to the Na+-sample. Interlayer collapse and migration of exchange cations into the montmorillonite lattice after heating to 220 ° C resulted in the oxidation of the VIFe2+ and a decrease in site distortion for IVFe3+. Similar spectral parameters for the Fe3+ resonances of both Na+ — and Li+-heated samples suggested the interlayer cations do not penetrate as far as the octahedral layers. In order to utilize the enhanced sensitivity of VIFe2+ Δ values to changes in EFG the Fe3+ in the heated montmorillonites was reduced to Fe2+ with hydrazine. Similar spectral parameters for both the Na+ — and Li+-exchanged montmorillonite were observed giving further evidence that Li cations do not migrate into vacant octahedral sites. 相似文献
12.
《Applied Geochemistry》2005,20(2):409-422
Bentonites have been proposed as buffer material for barriers in geological disposal facilities for radioactive waste. This material is expected to fill up by swelling the void between the canisters containing the waste and the surrounding ground. However, the bentonite barriers may be submitted to changes of humidity, temperature variation, fluid interaction, mass transport, etc. This could modify the physico-chemical performance of the barrier, mainly on the interface with the steel container and with the geological barrier. The engineered barrier development necessitates thus the study of the physico-chemical stability of its mineral component as a function of time under the conditions of the repository in the long-term. The aim of this paper is to apply a simplified method (volume balance in a saturated medium) to evaluate the swelling capacity evolution of a bentonite barrier because of their geochemical transformations by using a thermo-kinetic hydrochemical code (KIRMAT: Kinetic Reactions and Mass Transport “1D”).The system modelled here consists of 1 m thick zone of water-saturated engineered barrier. This non-equilibrated system is placed in contact with a geological fluid on one side, which is then allowed to diffuse into the barrier, while the other side is kept in contact with iron-charged solution (0.001 mol/kg H2O). The initial reducing conditions (; Eh = −200 mV) and a constant reaction temperature (100 °C) were considered.In the current study the decay of swelling capacity was considered directly proportional on the volume of transformed montmorillonite (cation exchange + geochemical transformation), taking into account that it may be partially compensated by the volume of neo-formed swelling-clays.The results showed that the swelling capacity of the engineered barrier is not drastically affected after about 3000 years of reaction and transport because the volume of neo-formed swelling clays is almost directly proportional on the volume of transformed montmorillonite. In fact, a graphical method predicted that the decay of swelling capacity of the engineered barrier lies between 11% and 14% when the montmorillonite is completely transformed (cation exchange + minimal geochemical transformation) in the system. 相似文献
13.
Benjamin Burton 《Physics and Chemistry of Minerals》1984,11(3):132-139
The cluster variation method, in the single prism approximation, is used to model phase relations in the system, Fe2O3-FeTiO3. Ordering in FeTiO3 is analyzed, and it is shown that the stabilization of FeTiO3 (relative to mechanical mixing of Fe2O3 and Ti2O3) includes: (1) a contribution from the redox reaction, Fe3++Ti3+→Fe2++Ti4+ (ΔH redox～?70kJ mole?1); and (2) a contribution from ordering (ΔH OD～?8kJ mole?1). A theoretical phase diagram is presented and compared with available experimental data. Semiquantitative agreement between theory and experiment (on the location of phase boundaries) is achieved; but, owing to the paucity of experimental data on coexisting phases, these results may be fortuitous. 相似文献
14.
P. K. Bhattacharyya Somnath Dasgupta M. Fukuoka Supriya Roy 《Contributions to Mineralogy and Petrology》1984,87(1):65-71
In the metamorphosed manganese oxide ores of India, braunite is ubiquitous in all assemblages from chlorite to sillimanite grades. Chemical analyses of braunite from different prograde assemblages confirm the presence of a fixed R2+ (=Mn2++Mg+Ca) SiO3 molecule in the mineral. Element partitioning between coexisting braunite and bixbyite indicates a near-ideal mixing of Fe+3/ -Mn+3 in the phases. This also indicates that braunite became relatively ferrian while equilibrating with associated phases such as bixbyite, hollandite and jacobsite during prograde reactions. Petrogenetic studies show that as a general trend, prograde lower oxide phases appeared by deoxidation of higher oxide phases. But braunite, a more reduced phase than bixbyite, appeared early from deoxidation of pyrolusite in presence of quartz. Bixbyite could appear later from the reacting pyrolusite-braunite-quartz assemblage. Inferred mineral reaction paths and the general trend of pro-grade deoxidation reactions suggest that the composition of ambient fluid phase was internally buffered during metamorphism. 相似文献
15.
Experimental evidence is reported for Fe2+ disproportionation in Al-free perovskite (Pv), when submitted to large temperature gradients (i.e., under off-equilibrium
conditions) in a laser heated diamond anvil cell (LHDAC). To enable this effect, the experimental procedure was designed to
produce large radial and axial temperature gradients. In the Pv and ferropericlase (Fp) assemblage synthesized after dissociation
of natural olivine, the three chemical states of iron (i.e., Fe0, Fe2+ and Fe3+) could be evidenced by electron probe microanalysis (EPMA), through variations of oxygen contents attached to the Fe cations.
Despite inherent difficulties for determination of O-contents and Fe3+/ΣFe ratios using EPMA, we recorded significant changes in iron oxidation state across the laser-heated strip. These changes
are correlated with variations in composition for the major elements (Fe, Mg, and Si), which evidences that the Pv/Fp assemblage
experienced large segregation under the strong temperature gradients. Grains of metallic iron were detected in parts of the
laser-heated strip coexisting with a Pv phase with Fe/(Mg + Fe) = 6 at% and most of its iron as Fe3+. This Fe2+-disproportionation reaction involves insertion of Fe3+-defects in the Pv lattice. This Fe3+-bearing Pv phase is presumably unstable and decomposes into a mineral assemblage including magnesioferrite, which is detected
at the border of the laser-heated strip. 相似文献
16.
RALPH KRETZ 《Journal of Metamorphic Geology》1990,8(5):493-506
Garnet-biotite gneisses, some of which contain sillimanite or hornblende, are widespread within the Otter Lake terrain, a portion of the Grenville Province of the Canadian Shield. The metamorphic grade is upper amphibolite to, locally, lower granulite facies. The atomic ratio Fe2+/(Fe2++ Fe3+) in biotite ranges from 0.79 to 0.89 (ferrous iron determinations in 10 highly pure separates), with a mean of 0.86. Mg and Fe2+ atoms occupy 67–78% of the octahedral sites, the remainder are occupied by Fe3+, Ti, and Al, and some are vacant. Mg/(Mg + Fe2+), denoted X, in the analysed samples ranges from 0.32 to 0.65. Garnet contains 1–24% grossular, 1–12% spessartine and X ranges from 0.07 to 0.34. Compositional variation in biotite and garnet is examined in relation to three mineral equilibria: (I) biotite + sillimanite + quartz = garnet + K-feldspar + H2O; (II) pyrope + annite = almandine + phlogopite; (III) anorthite = grossular + sillimanite + quartz. Measurements of X (biotite) and X (garnet) are used to construct an illustrative model for equilibrium (I) which relates the observed variation in X to a temperature range of 70°C or a range in H2O activity of 0.6; the latter interpretation is preferred. In sillimanite-free gneisses, the distribution of Mg and Fe2+ between garnet (low in Ca and Mn) and biotite is adequately described by a distribution coefficient (KD) of 4.1 (equilibrium II). The observed increase in the distribution coefficient with increasing Ca in garnet is ln KD= 1.3 + 2.5 × 10?2 [Ca] where [Ca] = 100 Ca/(Mg + Fe2++ Mn + Ca). The distribution coefficient is apparently unaffected by the presence of up to 12% spessartine in garnet. In several specimens of garnet-sillimanite-plagioclase gneiss, the Ca contents of garnet and of plagioclase increase in unison, as required by equilibrium (III). The mean pressure calculated from these data (n= 17) is 5.9 kbar, and the 95% confidence limits are ±0.5 kbar. 相似文献
17.
Iron sulfide oxidation and the chemistry of acid generation 总被引：3，自引：0，他引：3
Acid mine drainage, produced from the oxidation of iron sulfides, often contains elevated levels of dissolved aluminum (AI),
iron (Fe), and sulfate (SO4) and low pH. Understanding the interactions of these elements associated with acid mine drainage is necessary for proper
solid waste management planning. Two eastern oil shales were leached using humidity cell methods. This study used a New Albany
Shale (4.6 percent pyrite) and a Chattanooga Shale (1.5 percent pyrite). The leachates from the humidity cells were filtered,
and the filtrates were analyzed for total concentrations of cations and anions. After correcting for significant solution
species and complexes, ion activities were calculated from total concentrations. The results show that the activities of Fe3+, Fe2+, Al3+, and SO4
2− increased due to the oxidation of pyrite. Furthermore, the oxidation of pyrite resulted in a decreased pH and an increased
pe+pH (redox-potential). The Fe3+ and Fe2+ activities appeared to be controlled by amorphous Fe(OH)3 solid phase above a pH of 6.0 and below pe+pH 11.0. The Fe3+, Fe2+, and SO4
2− activities reached saturation with respect to FeOHSO4 solid phase between pH 3.0 and 6.0 and below pe+pH 11.0 Below a pH of 3.0 and above a pe+pH of 11.0, Fe2+, Fe3+, and SO4
2− activities are supported by FeSO4·7H2O solid phase. Above a pH of 6.0, the Al3+ activity showed an equilibrium with amorphous Al(OH)3 solid phase. Below pH 6.0, Al3+ and SO4
2− activities are regulated by the AlOHSO4 solid phase, irrespective of pe+pH. The results of this study suggest that under oxidizing conditions with low to high leaching
potential, activities of Al and Fe can be predicted on the basis of secondary mineral formation over a wide range of pH and
redox. As a result, the long-term chemistry associated with disposal environments can be largely predicted (including trace
elements). 相似文献
18.
Microscopic and spectroscopic studies were conducted to assess mineral transformation processes in aqueous suspensions of illite (Il), vermiculite (Vm) and montmorillonite (Mt) that were subjected to weathering in a simulated high-level radioactive tank waste leachate (0.05 m AlT, 2 m Na+, 1 m NO3−, pH ∼14, Cs+ and Sr2+ present as co-contaminants). Time series (0 to 369 d) experiments were conducted at 298 K, with initial [Cs]0 and [Sr]0 concentrations from 10−5 to 10− mol kg−. Incongruent clay dissolution resulted in an accumulation of secondary aluminosilicate precipitates identified as nitrate-sodalite, nitrate-cancrinite and zeolite X, by molecular spectroscopy and electron microscopy (XRD, IR, NMR, SEM-EDS and TEM-EDS). Contaminant fate was dependent on competing uptake to parent clays and weathering products. TEM-EDS results indicated that high Il affinity for Cs was due to adsorption at frayed edge sites. The Il system also comprised Sr-rich aluminous precipitates after 369 d reaction time. In Mt systems, Cs and Sr were co-precipitated into increasingly recalcitrant spheroidal precipitates over the course of the experiment, whereas contaminant association with montmorillonite platelets was less prevalent. In contrast, Cs and Sr were found in association with weathered Vm particles despite the formation of spheroidal aluminosilicate precipitates that were comparable to those formed from Mt dissolution. 相似文献
19.
In this study, the zeta potential of montmorillonite in the presence of different chemical solutions was modeled by means
of artificial neural networks (ANNs). Zeta potential of the montmorillonite was measured in the presence of salt cations,
Na+, Li+ and Ca2+ and metals Zn2+, Pb2+, Cu2+, and Al3+ at different pH values, and observed values pointed to a different behavior for this mineral in the presence of salt and heavy
metal cations. Artificial neural networks were successfully developed for the prediction of the zeta potential of montmorillonite
in the presence of salt and heavy metal cations at different pH values and ionic strengths. Resulting zeta potential of montmorillonite
shows different behavior in the presence of salt and heavy metal cations, and two ANN models were developed in order to be
compared with experimental results. The ANNs results were found to be close to experimentally measured zeta potential values.
The performance indices such as coefficient of determination, root mean square error, mean absolute error, and variance account
for were used to control the performance of the prediction capacity of the models developed in this study. These indices obtained
make it clear that the predictive models constructed are quite powerful. The constructed ANN models exhibited a high performance
according to the performance indices. This performance has also shown that the ANNs seem to be a useful tool to minimize the
uncertainties encountered during the soil engineering projects. For this reason, the use of ANNs may provide new approaches
and methodologies. 相似文献
20.
The Xiadong Alaskan-type complex shares much in common with typical Alaskan-type complexes worldwide, while showing some unique features in terms of mineral compositions. Olivine from the Xiadong dunites is characterized by extremely high Fo component of 91.7–96.7 and anomalously negative correlation of Fo with NiO, while chromite is featured by high 100 × Fe3+/(Fe3+ + Cr + Al) (>70), high 100 × Fe2+/(Fe2+ + Mg) (>70), high 100 × Cr/(Cr + Al) (>90), low MnO (<0.6 wt%) and TiO2 contents (<0.5 wt%). To investigate these particular features, we conducted petrographic observation and mineral composition analyses for the Xiadong dunite. A number of Fe and/or Ni sulfides and alloys occurring as inclusions in olivine and chromite indicate that base metal mineral segregation took place prior to crystallization of olivine and chromite and probably induced Fe and Ni depletions in olivine. The FeO and MgO variations in profile analyses from chromite to adjacent olivine are compatible with Fe-Mg exchange. The diffusion mechanism of Fe from olivine to chromite and Mg from chromite to olivine may have elevated both Fo of olivine and 100 × Fe2+/(Mg + Fe2+) ratio of chromite and further enhanced the decoupling of Fo and NiO in olivine. We thus suggest that base metal mineral segregation and Fe-Mg exchange play important roles in the extreme compositions of the Xiadong dunite. The Ni depletion of olivine and degree of Fe-Mg exchange between olivine and chromite may be used as indicators of mineralization in mafic-ultramafic intrusions. 相似文献