艾斯卡试剂熔矿、动态树脂交换——等离子体质谱法测定土壤样品中的痕量碘   总被引：1，自引：0，他引：1  

吴赫  王龙山  张艳  李雪莹 《陕西地质》2009,27(2):97-102

研究了电感耦合等离子体质谱法（ICP—MS）测定土壤样品中微量碘的可行性,对测定碘的条件作了部分改进及进一步优化。样品经艾斯卡试剂分解,热水提取,阳离子交换树脂动态分离溶液中大量的钠、铁、锌等阳离子,干过滤部分溶液,采用电感耦合等离体子质谱法（ICP—MS）直接测定溶液中的碘。本方法用国家标准物质进行验证,测定结果和标准值吻合。并用该法顺利完成了陕西省宝鸡地区多目标区域地球化学调查样品中碘的测定。  相似文献   

金云母-蛭石间层矿物阳离子交换容量的影响因素研究     

彭同江  孙红娟  孙金梅  刘海峰 《矿物岩石》2009,29(1)

采用氯化铵交换-原子吸收光谱法和CaCl2-甲醛缩合法测定3个金云母-蛭石间层矿物样品的各阳离子交换分量和阳离子交换总量,通过分析样品粒度和溶液pH值对阳离子交换容量的影响及晶层端面水解使表面荷电的特点,确定样品的等电点.结果表明,随着粒度的增大,样品的阳离子交换容量逐渐减小;随着pH值的增大,样品的阳离子交换容量先急剧减小(pH=2～5),后趋于平缓(pH=5～9),而后再急剧减小(pH=9～11.5),这些变化主要与晶层端面的水解作用和八面体片阳离子的溶出作用有关;样品的等电点为pH值≈9.研究结果对于排除端面水解作用对阳离子交换容量的影响和进一步确定蛭石晶层的层电荷具有重要的意义.  相似文献   

变价元素在找矿评价工作中的意义     

刘炳璋  杨泽湘 《四川地质学报》2007,27(1):66-70

自然界中的变价元素广泛存在,不同价态的元素具有不同的地球化学性状,反映了不同的氧化还原环境,在成矿过程中形成各具特征的元素组合和矿物组合。利用Eh—pH图解和部分变价元素不同价态地球化学特征,分析自然界中矿物的稳定性和不同价态元素的共存关系及迁移能力,从中提炼找矿信息,有利于提高野外找矿评价工作成果质量。  相似文献   

Effects of cation substitutions in garnet and pyroxene on equilibrium oxygen isotope fractionations   总被引：3，自引：0，他引：3  

M. J. KOHN  & J. W. VALLEY 《Journal of Metamorphic Geology》1998,16(5):625-639

High-grade metamorphic rocks were used to explore oxygen isotope fractionations between pyroxene and garnet, and to investigate the effects on fractionation factors of the cation substitutions Fe³⁺Al_?1 and Ca(Fe,Mg)_?1. Recrystallized, granulite facies (725 °C) wollastonite ores from the northern Adirondack highlands contain essentially only the minerals clinopyroxene (a Di–Hd solid solution)+garnet (a Grs–Adr solid solution)±wollastonite, and exhibit a systematic dependence of measured fractionations on the Fe³⁺ content of calcic garnet: Δ(Cpx–CaGrt)=(0.14±0.12)+(0.78±0.20)X_Adr and Δ(Wo–CaGrt)=(0.15±0.22)+(0.57±0.33)X_Adr. In eclogites formed at T ≤650 °C, measured compositions of Ca-poor garnet and omphacite combined with experimental data indicate that Ca-poor, Fe-rich garnet is enriched in ¹⁸O compared to both diopside and grossular: extrapolating to 1000 K, Δ(Alm–Di)≈c. 0.2 and Δ(Alm–Grs)≈c. 0.5. Orthopyroxene and clinopyroxene from Gore Mountain, New York, show a constant fractionation that is independent of rock type, as expected if they have the same closure temperature. These data imply Δ(Opx-Cpx)≈c. 0.7 at 1000 K. Measured fractionations among Ca-poor garnet, orthopyroxene, clinopyroxene and hornblende in the Gore Mountain rocks further indicate an ¹⁸O enrichment in Ca-poor garnet over Grs (≈c. 0.5 at 1000 K). The new measurements are indistinguishable from expected equilibrium values based on experiments for the minerals enstatite, diopside, grossular, wollastonite and feldspar, but consistently indicate a significant isotope effect for the simple octahedral cation substitutions Fe³⁺Al_?1 (Grs vs. Adr) and Ca(Fe,Mg)_?1 (Ca-poor garnet vs. Grs; Opx vs. Cpx). Neither cation substitution has been directly investigated for its effect on ¹⁸O/¹⁶O fractionation with experiments in silicates. Chemical characterization of minerals is required prior to petrological interpretation of oxygen isotope trends.  相似文献   

X射线荧光光谱法测定钒的原子价平均值   总被引：2，自引：1，他引：1  

孙伟莹  谭秉和 《岩矿测试》1998,17(3):193-196

用Ｘ射线荧光光谱法测定了一系列钒的氧化物混合物中Ｖ的Ｋβ谱线的精细结构,研究了钒的氧化物中Ｋβ谱峰参数随混合物平均原子价变化的规律,并利用所作的定标曲线对一些实际样品,如钒渣、磁铁矿中钒的平均原子价进行了定量测定。  相似文献   

氮迁移转化对地下水硬度升高的影响   总被引：15，自引：0，他引：15  

王东胜  沈照理 《现代地质》1998,12(3):431-436

城市地下水硬度升高是一个普遍的环境问题,研究表明地下水硬度高值区与硝酸盐污染在空间上的分布具有一致性。通过室内土柱试验和化学热力学模拟,讨论了污水入渗过程中氮迁移转化对水土系统钙镁迁移的影响。结果表明：在连续入渗条件下,阳离子交换作用是控制地下水硬度升高的主要过程;在间歇入渗条件下,硝化作用改变了土水系统的酸碱条件,使钙镁难溶盐溶解,导致地下水硬度升高。  相似文献   

铝对铬成矿地球化学的依存性和对抗性     

戚长谋 《吉林地质》1998,17(1):32-35,42

基于岩浆铬矿床与超镁铁质岩石的关系,从元素亲合性和共生规律的角度揭示了铝对铬成矿制约的主导作用。分析了铝和铬亲石、亲氧的二重性及其晶体化学的依存关系。论证了超镁铁Ｓｉ－Ｏ体系中铝丰度过高或过低均不利于铬的成矿。揭示了制约因素分散富集的因素都是在一定条件下互为依存和转化的。是在动态中的矛盾的对立和统一。  相似文献   

Hydrogen incorporation in orthopyroxene: interaction of different trivalent cations     

Roland?StalderEmail author  Stephan?Klemme  Thomas?Ludwig  Henrik?Skogby 《Contributions to Mineralogy and Petrology》2005,150(5):473-485

The incorporation of hydrogen into ferrosilite, Fe-bearing enstatite and orthopyroxene containing different trivalent cations (Cr³⁺ and Al³⁺, Cr³⁺ and Fe³⁺) was investigated experimentally at 25 kbar. Hydrogen concentration was determined by FTIR-spectroscopy on oriented crystal sections and by secondary ion mass spectroscopy, whereas Mößbauer spectroscopy and optical spectroscopy were used to characterise the valence state of Fe in orthopyroxene. Results suggest that hydrogen incorporation in ferrosilite is achieved by a similar mechanism as in pure enstatite. In Cr-bearing samples, however, hydrogen incorporation is reduced by the presence of other trivalent cations by an increased tendency to form Tschermaks substitutions, e.g. Si _T ⁴⁺ + Mg _M1 ²⁺ ? Al _T ³⁺ + Cr _M1 ³⁺ . Thus, hydrogen solubility in natural orthopyroxenes from the Earth’s mantle, containing significant amounts of Cr³⁺, Al³⁺, and Fe³⁺, may be much more limited than expected from their trivalent cation content, as a large fraction of the trivalent cations does not participate in H-incorporating reactions as 2 Mg _M1 ²⁺ ? M _M1 ³⁺ + V_M1 + H _i ⁺ .  相似文献   

Fe(II)-Na(I)-Ca(II) Cation Exchange on Montmorillonite in Chloride Medium: Evidence for Preferential Clay Adsorption of Chloride – Metal Ion Pairs in Seawater     

Laurent?Charlet  Christophe?TournassatEmail author 《Aquatic Geochemistry》2005,11(2):115-137

Fe(II)–Ca(II), Fe(II)–Na(I), and Fe(II)–Ca(II)–Na(I) exchange experiments on montmorillonite were performed in chloride background. These experiments show the possible sorption of Fe²⁺ and FeCl⁺ ion pairs in exchange site positions, a result confirmed with 77 K ⁵⁷Fe Mössbauer experiments. The sorption data were modeled and the cation exchange selectivity for Fe(II) were found to be nearly equal to that of Ca(II). Vanselow selectivity coefficients, for Na–Fe²⁺ and Na–FeCl⁺ reactions, were found to be equal to 0.4 (0.5 for Ca²⁺) and 2.3 (2.5 for CaCl⁺) respectively. High affinity of montmorillonite for chloride ion pairs seems to be a common mechanism as first stated by Sposito et al., (Soil Sci. Soc. Am. J. 47, 51–56, 1983a), and should have implications e.g., on the chemistry of suspended particles in seawater. Exchange selectivity coefficients derived from this study and others were used to model experimental data on river water and seawater equilibrated particles. The agreement between simulations and experimental data is very good. The simulation shows the predominance of monovalent ion (Na⁺ and chloride ion pairs) sorption on clay particles in seawater. This sorption of monovalent ions leads to the dispersion of particles in seawater and to the extension of a plume of particles spreading away from river deltas, such as that of the River Amazon.  相似文献   

Study on the cation substitution capacity of synthetic 1nm manganate     

Qian Jiangchu  T. A. Mellin 《海洋学报(英文版)》1996,15(3):345-354

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