Minéraux serpentineux extraits de péridotites serpentinisées des Alpes Occidentales

Complete physical and chemical data presented concern serpentine minerals choosen from epizonal to non metamorphic domains. It is tried to correlate well-studied serpentine minerals, generally coming from particular outcrops with the rock-forming ones known only through the microscope.It appears that ribbons filling serpentine veins in a serpentinized dunite, the whole mesh-structure of a non metamorphic serpentine, and bastite lamellae are made of lizardite. Antigorite, only serpentine mineral present in metamorphic domains, shows no significative difference between high-pressure facies (glaucophane schist) and low-pressure facies (green-schist). The data allow a better understanding of the serpentinization process. The geochemically antinomic behaviour of iron and magnesium is emphasized.     

Seismic wave velocity and anisotropy of serpentinized peridotite in the Oman ophiolite

Shallow seismic measurements in harzburgite from the Oman ophiolite performed in a zone where the maximum horizontal anisotropy is expected (vertical foliation and horizontal lineation) point to a dominant dependence of seismic properties on fracturing.

Optical microscopy studies show that microcracks are guided by the serpentine (lizardite) penetrative network oriented subparallel to the harzburgite foliation and subperpendicular to the mineral lineation, and that serpentine (lizardite) vein filling has a maximum concentration of (001) planes parallel to the veins walls. The calculated elastic properties of the oriented alteration veins filled with serpentine in an anisotropic matrix formed by oriented crystals of olivine and orthopyroxene are compared with seismic velocities measured on hand specimens.

Laboratory ultrasonic data indicate that open microcracks are closed at 100 MPa pressure, e.g. (J. Geophys. Res. 65, (1960) 1083) and (Proc. ODP Sci. Results Leg 118, (1990) 227). Above this pressure, laboratory measurements and modeling show that P-compressional and S-shear wave velocities are mainly controlled by the mineral preferred orientation. Veins sealed with serpentine are effective in slightly lowering P and S velocities and increasing anisotropy. The penetrative lizardite network does not affect directly the geometry of seismic anisotropy, but contributes indirectly in the fact that this network controls the microcrack orientations.

Comparison between seismic measurements of peridotite and gabbro in the same conditions suggest that P- and S-waves anisotropies are a possible discriminating factor between the two lithologies in the suboceanic lithosphere.     

陕西潼关-河南灵宝蛭石定向晶片X射线衍射研究

采用定向晶片法对陕西潼关一河南灵宝蛭石进行了X射线研究，结果表明河南灵宝石板沟和陕西潼关李家乡蛭石矿“蛭石”的矿物组成主要为金云母．蛭石的规则或不规则间层矿物；程村藏马峪“蛭石”的矿物组成主要为罕见的大片状绿泥石．蛭石的间层矿物。对比样品的定向晶片法与粉末法的X射线衍射谱可以发现，定向晶片法更能揭示晶片中不同晶层的间层结构特点，特别是对于分结型间层矿物，可以从衍射谱图上直接确定分结型间层的组元。     

蛭石精矿的有机改性试验

采用十六烷基三甲基溴化铵(HDTMAB)对蛭石精矿进行了有机改性,利用X射线衍射法(XRD)、红外光谱(IR)、差示扫描量热法(DSC)和热失重分析(TG)对蛭石精矿和有机改性蛭石进行了表征。实验结果表明,当反应液中蛭石与水的质量比为1∶10、反应温度在60~70℃时,HDTMAB的阳离子HDTMA进入绝大部分蛭石晶粒的晶层,将蛭石的晶层间距撑大,蛭石的(001)晶面间距d001从1.45986 nm增大到3.70134 nm。HDTMA进入了单晶颗粒之间,将蛭石颗粒分散成单晶颗粒。     

Ripple formation in combined transdirectional steady and oscillatory flow

Measurements are described of the geometry of ripples formed on beds of sand exposed to a steady current at right angles to an oscillatory flow. Four different sands were studied. The oscillation was produced by an oscillating tray set into the bed of a steady-flow flume. It was observed that straight-crested ripples formed by oscillatory flow would usually develop a ‘serpentine’ form when the superimposed steady current exceeded a certain limit. For amplitudes of the tray velocity U_∞ less than about 0.38 m s^-1 this limit corresponded to U_∞/ū_*c>31, where ū_*c is the shear velocity measured just upstream of the oscillating tray. It is suggested that the serpentine form is caused by the interaction of vortices carried back and forth between adjacent ripples. On this assumption, the wavelength of the serpentine form would be proportional to the product of period of oscillation and near-bed steady current velocity. The present measurements appear to support this hypothesis although there is also evidence that the wavelength is influenced by preferred spacing patterns between vortices. The measurements also show the ratio of the amplitude of the serpentine form to its wavelength to be approximately constant. Empirical relationships are derived relating ripple geometry to flow and sediment properties. It is observed that the influence of Reynolds number and sediment properties on the geometry is very weak. It is suggested that this is typical of ripples formed with relatively low sediment transport rates. It is also found that, under the present experimental conditions, the ripple spacing in the direction of oscillation is almost independent of the magnitude of the steady current and in close agreement with the wavelengths previously measured in an oscillating water tunnel. This suggests that the additional inertia effects associated with oscillating tray rigs were not sufficient to affect bed geometry under the present test conditions.     

有机蛭石的制备及其层间插层剂排布模式研究

对新疆尉犁蛭石进行钠化改型后用系列烷基季铵盐进行了有机插层处理,利用XRD对样品进行表征.结合季铵盐阳离子的理论几何尺寸,研究了季铵盐阳离子在蛭石晶层的结构和排布方式.结果表明,不同链长烷基季铵盐阳离子在蛭石晶层排列方式的演化途径不同,季铵盐用量和季铵盐阳离子的性质能影响季铵盐阳离子在蛭石晶层的排布方式.当季铵盐用量较低时,季铵盐阳离子在蛭石晶层形成平卧排列,当季铵盐用量较高时,季铵盐阳离子在蛭石晶层形成倾斜排列,且直链烷基越长,季铵盐阳离子在蛭石晶层间越易形成倾斜排列.     

营口蛇纹石玉负离子释放功能及机理探讨

营口玉是传统岫岩玉中的特别类型,它的物理化学特征及成矿类型均与传统岫岩玉不同。采用ETS-2能量测试系统、偏光显微镜、电感耦合等离子质谱仪等现代测试技术手段对营口蛇纹石玉负离子释放量及机理进行了研究。结果表明:营口蛇纹石玉具有很好的负离子释放功能(840～933个/cm³),接近都市公园水平(1 000～2 000个/cm³),甚至高于环境矿物材料电气石。营口玉释放负离子的根本原因是玉石内部放射性微量元素导致空气分子及水分子电离而产生负离子。具有生物和化学活性的蛇纹石与玉石内具有放射性的微量元素共同作用使营口玉具有较好的负离子释放功能。     

Oxygen isotopic variability associated with multiple stages of serpentinization, Duke Island Complex, southeastern Alaska

Ultramafic rocks of the Duke Island Complex in southeastern Alaska crystallized in a supra-subduction zone setting, but the serpentinization of olivine-bearing rocks involved the incursion of late-stage meteoric waters. Three textural types of serpentine (primarily lizardite) have been identified which in part reflect progress in reactions during multiple stages of fluid infiltration. The overall mesh texture of serpentine has been subdivided into a massive-type, found in dunites and wehrlites, and a dendritic-type found in wehrlites and olivine clinopyroxenites. Serpentine veins represent a late-stage in the hydrothermal alteration process. Both FeO contents and δ¹⁸O values of the three textural types of serpentine are variable at the centimeter scale. Magnetite abundance in association with serpentine is also variable with up to 5 vol% of magnetite found in samples with dendritic serpentine. Continued reaction of FeO-bearing serpentine with fluid appears to control the formation of most magnetite. Oxygen isotope ratios of the three textural types of serpentine are distinct, with the massive variety characterized by δ¹⁸O values between −3‰ and 3‰, the dendritic variety showing values between 2‰ and 6‰ and the veins having the highest values between 4‰ and 10‰. Although the δ¹⁸O values may vary by as much as 5‰ on the centimeter scale, δD values tend to show relatively less variation with over 90% of the measured values between −100‰ and −120‰. The O and H isotopic values are consistent with the involvement of meteoric water that had undergone variable degrees of isotopic exchange with country rocks prior to reacting with olivine in the Duke Island Complex. Small-scale variability in both serpentine FeO content and δ¹⁸O values suggests that chemical and isotopic equilibria may have not been attained at larger than centimeter scales. Oxygen isotopic variability in serpentine produced during relatively low-temperature hydrothermal alteration is in large part a function of exchange mediated via fluid flow through microfractures.     

有机插层蛭石对有机污染物苯酚和氯苯的吸附特性研究

分别应用溴化十六烷基三甲基溴化铵(HDTMA)和溴化十六烷基吡啶(HDPY)改性插层级石对苯酚和氮苯两种非离于型环境污染物进行吸附性能研究。结果表明，蛭石原矿对苯酚和氮苯的吸附能力很小，经表面活性剂处理后其吸附能力大大增强。有机插层级石对苯酚的吸附具有表面吸附特征，其吸附等沮线为Freundish型；而对氮苯的吸附实际上是氮苯在水相与有机级石中有机相之间的一种分配过程，其吸附等沮线为直线型。苯酚和氮苯的竞争吸附并末减弱有机蛭石对氯苯的吸附能力，反而由于它们同时存在产生协同效应，使有机插层蛭石对氯苯总的吸附能力有所提高。     

Sectors in polygonal serpentine. A model based on dislocations

Based on coexisting rolled chrysotile and polygonal serpentine fibers with 15 or 30 sectors each, a crystallographic model for polygonization of chrysotile is proposed. It is based on an assumed chrysotile-to-lizardite transition. Polygonization of chrysotile requires more likely 15 partial dislocations per turn, as required by polytype translational operators for serpentines. The observed number of sectors corresponds to the two most elastically stable arrays of dislocations. Homogeneous shear of the layer stacking arising from intersector kinking results in a cyclic distribution of twins and/or different polytypes. This makes the fiber axis a fivefold symmetry axis and consequently polygonal serpentine and chrysotile to be both forms of serpentine with local fivefold symmetry. This model is alternative to the recent crystallograpic model by Chisholm (1991, 1992).     

Partage du nickel entre serpentine et brucite au cours de la serpentinisation du péridot

When nickeliferous peridot is submitted to a serpentinisation reaction with formation of brucite, the peridotic nickel is partitioned between the two minerals (serpentine and brucite) with a distribution coefficient K=[(Ni/Mg) brucite]/[(Ni/Mg)] serpentine=1,63 (at 350°C and 1 kbar), in favour of brucite.     

Process of serpentinization in the ultramafic massif of Beni Bousera (internal Rif,Morocco)

The Beni Bousera massif forms part of the Sebtide units in the internal Rif Mountain (Morocco). It is mainly composed of mantle peridotites surrounded by crustal metamorphic rocks (kinzigites, micaschists, and schists). The serpentinization affects all of peridotite massif to various degrees. Serpentinization is concentrated at the top of the peridotites, along the mylonitized zone, and in the NE part of the massif. It is manifested by the formation of mesh and hourglass textures along the tectonic foliation in the highly serpentinized peridotites; and brecciated texture in the least serpentinized peridotites. Pyroxene minerals are still intact hosting few serpentine veins. These petrographic features are consistent with the geochemical data, marked by the increasing of LOI and decreasing of MgO and FeO toward the top of the massif and Aaraben fault. The Raman characterization of serpentine with the brecciated mesh and hourglass textures correspond to lizardite type whereas the serpentine with the vein texture is formed by lizardite + chrysotile.     

Uptake of fluoride by serpentine

Fluoride uptake by serpentine depends on a number of parameters, viz. the chemical composition of serpentine, its particle size, pH of the medium, etc. Exchangeable (OH)^? in serpentine minerals is essential for fluoride uptake. Data are also presented indicating the existence of an equilibrium between the fluoride concentrations in the solution and that taken up by serpentine over a wide range of experimental conditions. The available evidence strongly suggests the proxy of F^? for (OH)^? group as contributing to the principal mechanism of the process.     

含蛭石晶层间层矿物的可交换性阳离子及交换容量研究

对采自新疆尉犁蛭石矿、河南灵宝-陕西潼关蛭石矿的工业蛭石矿物样品进行了可交换性阳离子与交换容量研究，发现新疆尉犁蛭石矿金云母-蛭石中可交换性阳离子主要为Na^ 和Ca^2 ，其次为Mg^2 、K^ 、Ba^2 和Sr^2 ；而河南灵宝-陕西潼关蛭石矿工业蛭石样品的可交换性阳离子主要为Ca^2 和Mg^2 ，其次为Na^ 、K^ 等。金云母-蛭石和绿泥石-蛭石间层矿物的阳离子交换容量随间层结构中蛭石晶层的含量增加而增大，一般在56．92～98．95mmol／100g之间，仅为蛭石最大阳离子交换容量的一半。金云母-蛭石样品阳离子交换容量大小与K2O含量呈负相关关系，与(Na2O CaO)含量呈正相关关系。     

Vermiculite bio-barriers for Cu and Zn remediation: an eco-friendly approach for freshwater and sediments protection

The increase in heavy metal contamination in freshwater systems causes serious environmental problems in most industrialized countries, and the effort to find eco-friendly techniques for reducing water and sediment contamination is fundamental for environmental protection. Permeable barriers made of natural clays can be used as low-cost and eco-friendly materials for adsorbing heavy metals from water solution and thus reducing the sediment contamination. This study discusses the application of permeable barriers made of vermiculite clay for heavy metals remediation at the interface between water and sediments and investigates the possibility to increase their efficiency by loading the vermiculite surface with a microbial biofilm of Pseudomonas putida, which is well known to be a heavy metal accumulator. Some batch assays were performed to verify the uptake capacity of two systems and their adsorption kinetics, and the results indicated that the vermiculite bio-barrier system had a higher removal capacity than the vermiculite barrier (+34.4 and 22.8 % for Cu and Zn, respectively). Moreover, the presence of P. putida biofilm strongly contributed to fasten the kinetics of metals adsorption onto vermiculite sheets. In open-system conditions, the presence of a vermiculite barrier at the interface between water and sediment could reduce the sediment contamination up to 20 and 23 % for Cu and Zn, respectively, highlighting the efficiency of these eco-friendly materials for environmental applications. Nevertheless, the contribution of microbial biofilm in open-system setup should be optimized, and some important considerations about biofilm attachment in a continuous-flow system have been discussed.     

HDTMA改性蛭石的结构特征研究

用十六烷基三甲基溴化铵 (HDTMA·Br)对蛭石矿物进行改性 ,制成有机蛭石。应用X射线衍射分析、差热分析等对有机蛭石结构进行研究。结果显示 ,HDTMA能较容易地进入蛭石矿物的层间域 ,以倾斜立式在层间排列 ,倾角约为 5 7°。蛭石与HDTMA之间的反应 ,在HDTMA加入量较少时以离子交换为主 ;在HDTMA加入量较多时 ,分子吸附也变得重要。当HDTMA加入量小于蛭石的阳离子交换容量时 ,HDTMA将尽量以紧密排列方式进入部分蛭石层间 ,进入蛭石层间的HDTMA具有较好的稳定性 ,不易解吸。     

层间水含量对蛭石有机改性影响的研究

本文以溴代十六烷基吡啶、磷酸三丁酯对膨胀蛭石和未膨胀蛭石进行了改性处理，并用IR、XRD方法研究了蛭石在不同层间水含量情况下，这两种有机分子分别进入蛭石层间的难易情况，结果表明：（1）层间水含量能够对有机分子进入蛭石层间产生影响，但对具有较强离子交换能力的有机分子进入层间的影响不大；（2）磷酸三丁酯分子易于与含层间水少的膨胀蛭石结合，说明层间水对磷酸三丁酯分子的作用遵循异极性排斥的原则。     

高表面活性矿物对Zn~(2+)的吸附机理及其环境意义

本文利用高表面活性矿物蒙脱石、蛭石、沸石在一定的介质条件下对Zn2 +进行吸附实验研究。蒙脱石和蛭石对Zn2 +的等温吸附线呈双“S”型 ,而沸石对Zn2 +的等温吸附线则呈“Langmuir”型。三种矿物对Zn2 +的吸附容量大小顺序为 :蒙脱石 >蛭石 >沸石。运用粉晶X射线衍射、红外光谱、差热及热重分析等技术对矿物及矿物吸附Zn2 +后的结构特征进行了研究。结果表明 ,蒙脱石吸附锌后其层间域中吸附锌大量水解形成新的物相 ,而蛭石与沸石吸附锌后水解很少。这为利用高表面活性矿物控制和治理环境污染及其可循环利用提供了理论依据。     

X射线粉晶衍射仪在辽宁瓦房店金伯利岩蚀变矿物鉴定中的应用

瓦房店金伯利岩热液蚀变强烈,原岩矿物组分几乎蚀变殆尽,显微镜下对蚀变矿物鉴定相当困难.利用X射线粉晶衍射技术对蚀变金伯利岩物相进行系统检测,结果显示：42号岩管金伯利岩主要矿物为蛇纹石、金云母和滑石,有少量方解石、锐钛矿、磷灰石、石英、钛铁矿、钙钛矿、榍石、磁铁矿和绿泥石;石灰窑1号无矿金伯利岩岩管主要矿物为蛇纹石、金云母和白云石,有少量方解石、锐钛矿、磷灰石、滑石、磁铁矿和绿泥石;9号无矿金伯利岩岩脉主要矿物为方解石和石英,有少量绿泥石和重晶石;51号贫矿金伯利岩岩管主要矿物为蛇纹石和金云母,方解石化作用不均匀,白云石化作用普遍,有少量锐钛矿、滑石、磁铁矿、绿泥石、磷灰石、钛铁矿、石英;30号贫矿岩管样品风化严重,主要矿物为蒙脱石,有少量方解石、滑石、蛇纹石、榍石、磷灰石.实践证明,采用X射线粉晶衍射仪鉴定金伯利岩蚀变矿物组合是一种非常可行的技术手段.     

The stoichiometric effects of ferric iron substitutions in serpentine from microprobe data

ABSTRACT

Given that secondary magnetite is common in serpentinites, it is clear that serpentinites are oxidized rocks. Questions remain, however, concerning the distribution of ferric iron among magnetite and serpentine minerals and the role of ferric iron-rich serpentine in the formation of secondary magnetite. Direct determination of ferric iron in serpentine is not possible using an electron microprobe. We show, however, that the stoichiometic effects of ferric iron substitutions are detectable, although not quantifiable, by microprobe. First, we demonstrate that for studies that provide both microprobe analyses of major elements of serpentine and Mössbauer analysis of ferric iron, substitution effects are obvious. Next, it is equally clear that the early veins forming at the onset of olivine hydration (type 1 veins) show no indication of the presence of ferric serpentine, although a small amount of ferric ‘brucite’ may occur. Finally, we show that secondary (type 2) veins, which form as the system becomes open to fluids in equilibrium with plagioclase or pyroxene, contain, in addition to significant alumina, stoichiometric indications of ferric iron substitution. The serpentine in these veins is magnesian, usually with Mg#s around 96–98. Thus, even if a significant proportion of this iron is ferric, it comprises only a small fraction of the total ferric iron budget of the rock. Given that reduced iron is known to be abundant in early-formed brucite and early-formed serpentine and given that brucite, in particular, is absent from evolved serpentine veins, we propose that most magnetite in serpentinites forms as a tertiary product via oxidation of brucite.