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首页> 外文期刊>American Journal of Science >CRYSTAL CHEMISTRY OF KAOLINITE AND Fe-Mn OXIDES: RELATION WITH FORMATION CONDITIONS OF LOW TEMPERATURE SYSTEMS
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CRYSTAL CHEMISTRY OF KAOLINITE AND Fe-Mn OXIDES: RELATION WITH FORMATION CONDITIONS OF LOW TEMPERATURE SYSTEMS

机译：高岭石和Fe-Mn氧化物的晶体化学性质：与低温系统形成条件的关系

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摘要

Recent data on the crystal chemistry of Earth's Surface minerals obtained using spectroscopic methods are reviewed. Two methods, X-ray Absorption Spectroscopy (XAS) and Electron Paramagnetic Resonance (EPR), have received particular attention. The results described include: intracrystalline distribution of cations in kaolinite and some other phyllosilicates and Fe- and Mn-oxides; interpolyhedral relationships in oxide minerals and hydrous gels; complexation mechanisms for transition elements at surfaces of oxides and silicates (outer-sphere, mono- and polynuclear inner-sphere complexes); and finally, the significance of radiation-induced defect centers. Mineralogical and geochemical implications include: non-ideal mixing of elements in solid-solutions; the existence of specific modes of intersite distribution including the segregation of atoms; recognition, at the molecular level, of reactive surface sites that have structural control over sorption efficiency and reaction kinetics; and the transport of short-lived isotopes and their relationship with processes of weathering, hydrother-mal alteration, and formation of sedimentary basins. Information from spectroscopic methods has resulted in a better understanding of some of the geochemical processes that control the surface and bulk composition of minerals. One application is the study of mineral formation at the Earth's surface. Defect centers and paramagnetic impurities are effective fingerprints of kaolin origin. The presence of Mn~(2+) outersphere and vanadyl innersphere complexes provides clues about the evolution of physico-chemical conditions during the formation of laterites and sediments, respectively. A second application is to environmental geochemistry and, in particular, to the migration and containment of radioactive and toxic wastes. An understanding of heavy metal trapping by mineral surfaces provides a rationale for modeling soil contamination and for choosing appropriate materials for rehabilitation. Furthermore, comparison of a total accumulated dose with present-day geochemical data provides an assessment of radionuclide migration in the geosphere.
机译：回顾了使用光谱法获得的有关地球表面矿物晶体化学的最新数据。 X射线吸收光谱（XAS）和电子顺磁共振（EPR）这两种方法受到了特别的关注。描述的结果包括：高岭石和其他一些页硅酸盐以及铁和锰的氧化物中阳离子的晶内分布；氧化物矿物和水凝胶中的多面体关系；氧化物和硅酸盐表面上的过渡元素的络合机理（外球，单核和多核内球络合物）；最后，辐射诱发的缺陷中心的重要性。矿物学和地球化学意义包括：固溶体中元素的非理想混合；是否存在特定的站点间分布模式，包括原子的分离；在分子水平上识别对吸附效率和反应动力学具有结构控制的反应性表面位点；以及短命同位素的迁移及其与风化，水热变化和沉积盆地形成的关系。来自光谱方法的信息已使人们更好地了解了控制矿物表面和整体成分的一些地球化学过程。一种应用是研究地球表面的矿物形成。缺陷中心和顺磁性杂质是高岭土来源的有效指纹。 Mn〜（2+）外层和钒基内层复合物的存在分别为红土和沉积物形成过程中理化条件的演变提供了线索。第二个应用是环境地球化学，尤其是放射性和有毒废物的迁移和封闭。对矿物表面捕获重金属的理解为建模土壤污染和选择适当的修复材料提供了依据。此外，将总累积剂量与当今的地球化学数据进行比较，可以评估放射性核素在地球圈中的迁移。

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