Morphological Characteristics of （K, Na）-Rectorite from Zhongxiang Rectorite Deposit, Hubei, Central China

The morphological characteristics of the Zhongxiang (钟祥) rectorite have been studied using X-ray diffraction (XRD), electron probe micro-analyzer (EPMA), scanning electron microscopy (SEM), atomic force microscope (AFM), and high-resolution transmission electron microscopy (HRTEM). The structural formula of the Zhongxiang rectorite is: interstratification of (K, Na)-mica and Ca-montmorillouite. SEM observations show that Zhongxiang rectorite occurs as platy and fold-shaped crystals, and mainly as extremely thin plates with thickness ranging from 0.4 to 0.05 μm and a smooth (001) surface. There are well-developed polygonal steps on the surfaces of some thick crystals, suggesting a layer-by-layer growth mechanism. AFM observations show a series of steps with a height of 2 nm on the platy particles, suggesting the stacking of 20 nm fundamental particles. Club-like or fiber-shaped halloysite is included in the platy crystals with their elongated dimension paralleling (001) of the platy crystals or crossing the (001) surface of the platy rectorite, indicating multi-stage crystallization and involvement of hydrothermal fluids. The Zhongxiang rectorite was generated by both layer-by-layer growth mechanism and dissolution and crystallization growth mechanism with multistages.     

贵州省黔西县枫香地区上二叠统龙潭组埃洛石矿物学特征及成因分析

研究了贵州省黔西县枫香地区上二叠统龙潭组埃洛石,运用显微鉴定、X射线衍射、红外光谱、差热和热重分析、扫描电镜与能谱分析方法及地球化学分析,对埃洛石黏土矿物进行准确定性定量分析。研究表明,埃洛石主要组成为10A—管状埃洛石、铁质、炭质,岩石富SiO₂、Al₂O₃,贫K₂O、Na₂O、CaO、MgO,为酸性岩溶水淋滤炭质、泥质碎屑岩和碳酸盐岩中的硅铝质物质,经分解、溶胶、絮凝充填、脱水老化结晶而成。     

Development of Sulfuric Acid Speleogenetic Deposits within Cavernous Middle Eocene Beds: Inference on Hydrocarbon Gas Seepages,Giza Pyramids Plateau,Egypt

Development of sulfuric acid speleogenetic mineral deposits within cavernous middle Eocene beds of the Pyramids plateau is linked to hydrocarbon gas seepages. The work carried out field observations, binocular, polarizing, scanning and transmitted electron microscopy investigation, X-ray diffraction and X-ray fluorescence analyses. The morphological and petrographic features and chemical composition of the studied mineral deposits reveal a hypogene sulfuric acid speleogenesis. A model comprised of the following stages can be used to explain the presence of these features. (1) Ascent of hydrogen sulfide (H2S) gas associated with hydrocarbon seepages from the Cretaceous reservoirs under reducing conditions followed by oxidation to sulfuric acid (H2SO4), (2) descent of carbonic acid (H2CO3)-rich solution generated from surface sources, (3) reaction of H2SO4 and H2CO3 with the calcareous and argillaceous host rocks, (4) formation of H2SO4 speleogenetic by-products represented by natroalunite, aluminium-phosphate-sulfate, hydrated halloysite and Fe/Mn oxides within the replacive gypsum, and (5) subsequent stresses due to the formation of nearby stratiform cavities gave rise to the development of fractures/veinlets filled with displacive fibrous satinspar gypsum. The study sets the paleokarst features of the Giza Pyramids plateau within a hypogene sulfuric acid karst system developed by the action of groundwater containing H2S, H2SO4 and H2CO3.     

四川北川埃洛石矿物学特征及工业利用前景

本文对四川北川埃洛石的矿物学特征进行研究表明，埃洛石呈管状，其ＴＦｅ２Ｏ３，ＴｉＯ２，ＭｎＯ等杂质含量低，其化学成分接近理论值，ＸＲＤ，ＩＲ，ＤＴＡ等分析均表明其为埃洛石矿物。对埃洛石的主要工艺性能测试研究表明，北川埃洛石型粘土具有优良的工艺性能，应用前景广阔。     

琼北火山喷发物风化特征的研究与应用

通过X光衍射、扫描电镜和能谱分析发现 ,琼北雷虎岭 -马鞍岭地区火山喷发物风化形成的次生黏土主要是球状和不规则球状富铁埃洛石 ,随着风化时间的增长 ,埃洛石的转变顺序为 10 埃洛石→ ( 10 + 7 )埃洛石→ 7 埃洛石 ,据此推测该地区火山喷发的先后顺序为雷虎岭东南→儒红村北→儒红村东。喷发年代在 6 0 0 0～ 12 0 0 0aBP之间     

Dévitrification et altération supergène d'une rhyolite (bassin du Paraná, Brésil) : mécanismes et bilans géochimiques

The weathering of a rhyolitic lava flow of the Paraná Basin (Brazil) developed, on few centimeters only, simplified petrographic features. The initial meteoric fluid pass-way is marked by celadonite-to-nontronite transformation. The second step is the complete dissolution of plagioclases, and the last one is the massive precipitation of halloysite. The geochemical mass balances according to the alteration features demonstrate the progressive leaching of major and trace elements fractionated by plagioclases, glass and opaques, and the sorption of Cu>As>Sb in the halloysite matrix. To cite this article: M. Bernard et al., C. R. Geoscience 336 (2004).     

Hydrothermal synthesis of kaolinite illustrated by X-ray diffractograms and scanning electron micrographs,part II

Summary The hydrothermal synthesis of kaolinite from various alumina and silica starting materials reacted at 200°C in aqueous solutions of oxalic acid and H₂SO₄ with the corresponding saturated water vapour pressure, in periods of time from 10 to 25 days, has been followed by X-ray diffraction measurements, scanning electron microscopy, and energy dispersive analysis of the products. The temperature and time periods of reactions were chosen on the basis of previously collected data on the effects of H₄EDTA, a complex-forming agent, and of H₂SO₄, an inorganic acid, on the rate of formation of kaolinite. Aluminium-complexing acids increase the rate of formation or decrease the temperature of formation of kaolinite as shown by evidence from X-ray diffraction patterns. The influence of the starting materials as sources of aluminum, amorphous aluminum hydroxides, pseudoboehmite, allophane or gibbsite, has also been examined by X-ray diffraction, scanning electron microscopy, and by energy dispersive analysis. Scanning electron micrographs indicated that silica is a more mobile phase than alumina, based on the progressive formation of a thin coating on gibbsite during early reaction, then by growth of clusters of platy crystals of kaolin, and finally by production of pellets of stacked crystal flakes. Where gibbsite was used in the reaction mixture, boehmite was commonly observed as an intermediate phase.With 16 Figures     

湖南辰溪仙人湾埃洛石型高岭土的矿物学特征与成因简析

运用化学成分分析、X射线衍射、红外吸收光谱、差热-热重分析以及扫描电镜等研究手段，着重研究了湖南辰溪仙人湾高岭土矿的矿物学特征，并结合矿床的地质成矿特征讨论了其成因机制。研究表明，该矿床除有极少量碎屑状石英以及附着于埃洛石外表面的凝胶成因石英外，以10A埃洛石为主，部分为7A埃洛石；埃洛石为形态完整的管状晶体，管长一般为1．0-1．5μm，外径一般0．05-0．1μm。认为该矿床为古岩溶洞穴胶体沉积型埃洛石矿床。     

Microstructure and Photocatalytic Decomposition of Methylene Blue by TiO2-Mounted Halloysite, a Natural Tubular Mineral

On the basis of analysis of structure and properties, halloysite, a natural tubular mineral, was developed for an environmental treatment. TiO2 was mounted into halloysite by using hydrolysis of tetrabutyl titanate at room temperature. The adsorption and photocatalytic performance of halloysite and TiO2-mounted halloysite have been examined in methylene blue aqueous solution in the dark and under ultraviolet ray irradiation, respectively. Their performance of adsorption and photodecomposition was evaluated from the adsorbed and degraded amounts of methylene blue （MB）. Due to the mixture of adsorption and photodecomposition, the concentration of MB, organic pollution, in water decreased rapidly with TiO2-mounted halloysite powder, which is a faster reaction than that with halloysite-only adsorption. This new use of halloysite is leading to many interesting applications in the decomposition and elimination of various pollutants in air and water.     

湖南辰溪仙人湾埃洛石的表面吸附性能研究

通过N2吸附-解吸附、表面电位测试及透射电镜等手段研究了湖南辰溪仙人湾埃洛石的表面吸附性能。本区埃洛石属中空管体,吸脱附等温线属于Ⅱ类等温线。由BJH方程计算孔径在2.5~200 nm之间均有分布,集中在3~40 nm之间,由HK方程计算微孔集中分布在0.6~1.9 nm之间。天蓝色埃洛石孔隙丰富,以中微孔为主,纯白色埃洛石孔隙发育程度相对较低,以微、中、大孔为主。埃洛石的表面零电点接近pH=2。在pH=5~10之间,Zeta电位趋向稳定在-40 mV左右。本区埃洛石比表面积为35~87 m2/g,平均孔径为16.20~30.12 nm,具有很强的气体吸附能力和离子交换吸附能力。天蓝色埃洛石表面吸附性能最强,是优先考虑的开发对象。