An infrared spectroscopic and single-crystal X-ray study of malayaite, CaSnSiO5

Powder infrared spectroscopy and X-ray diffraction techniques on single crystals were used to study the thermal behaviour of malayaite, CaSnSiO₅. Infrared spectra show a discontinuity in the temperature evolution of phonon frequencies and absorbance near 500 K. However, crystal structure data collected at 300, 450, 550, 670, and 750 K show no evidence of a symmetry-breaking phase transition and no split positions. The most obvious change with heating is a tumbling motion of the SnO₆ octahedra and an increase of the anisotropic displacement factors of Ca. The thermal evolution of the mean-square vibrational amplitude of the Ca atom shows a pronounced change in slope near 500 K. The evidence suggests that the 500 K anomaly in malayaite is more similar in character to the 825 K (β-γ) transition as opposed to the 496 K (α-β) transition in synthetic titanite. Received: 26 March 1998 / Revised, accepted: 23 December 1998     

海带对重金属的吸附位点研究

用甲醇、甲醛处理海带藻粉,对其吸附重金属时羧基和氨基的作用进行研究,经藻粉的红外光谱及吸附实验的分析结果表明;羧基和氨基均参入了吸附过程;化学处理降低了重金属的吸附量。     

四川米易海塔地区混合岩型铀矿流体包裹体特征

混合岩型铀矿是康滇地轴上最有希望取得找矿突破的铀矿类型,海塔地区的铀矿化即是该类型铀矿的典型代表。本文针对区内的长英质脉矿石、富晶质铀矿石英脉矿石和含矿热液石英脉中的石英流体包裹体进行了研究。结果表明,海塔地区混合岩型铀矿的成矿作用可分为2个阶段:早期混合岩化热液成矿阶段为高温、中低盐度流体,流体包裹体均一温度集中在380~540℃,盐度变化范围为16.15%~23.18%NaCl eqv,是区内铀成矿的主要阶段;晚期热液叠加改造成矿阶段为中低温、低盐度流体,流体包裹体均一温度集中在140~220℃,盐度变化范围为5.56%~23.18%NaCleqv,是区内富铀矿的形成阶段。流体包裹体的气相成分测试表明,长英质脉矿石石英包裹体中以CH4、CO2为主,其次为H2O和N2;而富晶质铀矿石英脉及含矿热液石英脉石英包裹体中以H2为主,部分含有CO2、CH4、H2O。氢、氧同位素研究表明,早期混合岩化成矿阶段的成矿流体可能为岩浆水与变质水的混合,而晚期热液叠加改造成矿阶段成矿流体中可能有大气降水的加入。     

Provenance discrimination of fine sediments by mid-infrared spectroscopy: Calibration and application to fluvial palaeo-environmental reconstruction

Determining sediment provenance allows a better understanding of fluvial palaeo-dynamics, and identifying involved watersheds, at broad spatio-temporal scales. Conventional approaches for source identification are usually based on the physical, mineralogical, geochemical, magnetic or isotopic properties of sediments. Rapid, non-destructive and, in well-established contexts, highly accurate, mid-infrared spectroscopy is an alternative method for investigating sediment sources. The present research objectives are: (i) to use the mid-infrared spectroscopy method to discriminate the provenance of fine sediments, by applying discriminant analysis on a large set of reference samples from three different watersheds in the Upper Rhine area (associated with the Rhine, Ill and Vosges tributaries); (ii) to clarify whether the provenance spectra signatures are influenced by riverine depositional contexts (bars versus banks) and, to some extent, by grain size and/or high organic matter content; and (iii) to apply the mid-infrared spectroscopy – discriminant analysis method to a study of fluvial palaeo-dynamics and determine the provenance of palaeo-channel infillings. Three main sedimentary sources, divided into eight sub-categories, have been characterized by 196 modern reference samples from 78 collecting sites. Discriminant analysis displayed a strong separating power by classifying correctly the origin of samples without any inter-group overlap, independently from the geomorphological context (bar or bank) and associated slight changes in organic matter contents or grain size. Mid-infrared spectroscopy – discriminant analysis investigations of the palaeo-channel infill, complemented by radiocarbon dates and mineralogical data, allowed reconstructing general trends for the local morpho-sedimentary dynamics over the last ca 12 millennia.     

大洋多金属结核中铁锰质矿物拉曼光谱特征初探

拉曼光谱是一种快速无损的分析手段,它既可观察样品的显微结构构造,也可分析样品的成分和结构。为了丰富多金属结核的岩石矿物学特征,文章对西太平洋某海山区的多金属结核样品进行了X射线粉末衍射分析和拉曼光谱分析。X射线分析结果显示该区域样品主要含有水羟锰矿、钡镁锰矿、斜长石、钙十字沸石和石英,显微构造主要有纹层状构造、柱状构造、树枝状构造、充填构造等。通过分析对比潮湿样品和烘干样品铁锰质矿物的拉曼特征谱峰,得出结核中水羟锰矿的特征谱峰位于490 cm~(-1)、570 cm~(-1)和626 cm~(-1)附近,钡镁锰矿的特征谱峰则位于640 cm~(-1)附近,与陆地上对应矿物的特征拉曼谱峰不同。结核中的钡镁锰矿结构不稳定,经过风干或者抛磨后部分产生相变,不同显微结构中,相变情况不同。经与RRUFF数据库比对,识别出钙十字沸石、斜长石等自形晶,多分布于结核最内层,往结核外层总体减少。矿物微晶多见铁锰质矿物微晶和钙十字沸石微晶,铁锰质矿物绕其向外生长。     

祖母绿产地鉴别研究综述

祖母绿是一种名贵彩色宝石,其产地来源对祖母绿价值的评定具有重要影响。祖母绿的产地鉴别因而成为宝石实验室的重要技术,也是宝石学领域的研究热点。祖母绿的包裹体、谱学特征和化学成分是常用且关键的产地鉴别信息,但随着祖母绿产地研究数据的积累,传统的产地鉴别方法备受挑战。文章系统整理和归纳分析了全球各产地祖母绿的宝石学特征、包裹体信息、谱学特征和主微量成分数据,在综述前人研究结果的基础上,系统阐明了目前祖母绿产地鉴别的研究现状,总结了不同产地祖母绿的宝石学特征和包裹体特征,划分了紫外-可见光-近红外(UV-VIS-NIR)光谱类型,揭示了各产地祖母绿的成分指纹信息,并以案例的形式阐明区分祖母绿常见重要产地的方法。全球尺度的对比虽然表明不同产地祖母绿包裹体种类多数雷同、光谱趋同、成分含量范围重叠明显,但也从包裹体出现频率、UV-VIS-NIR光谱样式类型、重水吸收样式和成分投图参数的选择上提供了产地鉴别的新思路。综上所述,文章旨在促进祖母绿鉴别技术的发展,为祖母绿的产地溯源提供科学依据。     

福建云霄石榴子石宝石矿物学特征

福建云霄是我国重要的宝石级石榴子石产地,然而该区石榴子石的致色机理不清,制约了对其形成机制的理解及后续开发利用。本文选取7件福建云霄橙黄-橙红色石榴子石样品,利用傅立叶红外光谱、紫外-可见光光谱和拉曼光谱分析其谱学特征,使用电子探针及激光剥蚀电感耦合等离子体质谱仪(LA-ICP-MS)分析限定其主量、微量元素组成。结果表明云霄石榴子石主要为锰铝榴石,其颜色主要与二价锰(Mn²⁺)和铁离子(Fe²⁺)对可见光的吸收有关,Mn²⁺导致其主体呈橙色,少量Fe²⁺控制其橙红色调,微量Ti⁴⁺使其呈褐色调。福建云霄石榴子石样品核部锰含量相对较低而铁、镁含量较高,锰元素含量由核部向边部逐渐升高,且具有重稀土元素富集、轻稀土元素亏损的左倾配分模式和Eu负异常,表明其形成于岩浆结晶作用晚期。     

A new occurrence of retrogressed eclogite from the Sanbagawa belt of southwest Japan and its significance

The present paper reports, for the first time, the occurrence of an omphacite‐bearing mafic schist from the Asemi‐gawa region of the Sanbagawa belt (southwest Japan). The mafic schist occurs as thin layers within pelitic schist of the albite–biotite zone. Omphacite in the mafic schist only occurs as inclusions in garnet, and albite is the major Na phase in the matrix, suggesting that the mafic schist represents highly retrogressed eclogite. Garnet grains in the sample show prograde‐type compositional zoning with no textural or compositional break, and contain mineral inclusions of omphacite, quartz, glaucophane, barroisite/hornblende, epidote and titanite. In addition to the petrographic observations, Raman spectroscopy and focused ion beam system–transmission electron microscope analyses were used for identification of omphacite in the sample. The omphacite in the sample shows a strong Raman peak at 678 cm^?1, and concomitant Raman peaks are all consistent with those of the reference omphacite Raman spectrum. The selected area electron diffraction pattern of the omphacite is compatible with the common P2/n omphacite structure. Quartz inclusions in the mafic schist preserve high residual pressure values of Δω₁ > 8.5 cm^?1, corresponding to the eclogite facies conditions. The combination of Raman geothermobarometries and garnet–clinopyroxene geothermometry gives peak pressure–temperature (P–T) conditions of 1.7–2.0 GPa and 440–540 °C for the mafic schist. The peak P–T values are comparable to those of the schistose eclogitic rocks in other Sanbagawa eclogite units of Shikoku. These findings along with previous age constraints suggest that most of the Sanbagawa schistose eclogites and associated metasedimentary rocks share similar simple P–T histories along the Late Cretaceous subduction zone.     

基于近红外光谱技术的烃类与粘土矿物识别及其地质意义

沉积岩中自生粘土矿物受成岩过程中物化条件控制,是成岩系统物化条件的指示。近红外反射光谱技术对粘土矿物反应灵敏,在金属矿产勘探中已经得到了日益广泛的应用。首次对油气勘探地质井的试验工作,验证了近红外光谱数据不仅可以第一时间从岩石样品中直接提取微量烃信息,还能解译详细的粘土矿物组合及其变化,从而获取对油气勘探有价值的成岩温度和热成熟度信息。对鄂尔多斯富县地区试验样品的数据分析表明,生油和储油层中的粘土矿物组合(包括铵伊利石、绿泥石、高岭石)变化直接反映了成岩和构造演化物化条件的变化,对于全面理解盆地的环境条件并且判断油气生成的有利区位具有实际应用意义。     

Extent and nature of hydrocarbon occurrence in the groundwater of Kuwait

A study, aimed at characterizing the nature of anthropogenic and biogenic hydrocarbon contamination in the groundwater of Kuwait, was carried out using fluorescence spectroscopy and other analytical techniques. The results of these analyses have demonstrated that the groundwater in certain areas of northern Kuwait has been significantly impacted by contamination originating from the oil-contaminated surface soils. The study revealed that a water-soluble fraction (WSF) of the crude oil surface contamination appeared to be slowly leaching into the freshwater lenses located in the area. The study also showed that hydrocarbon pollutants were practically absent in the brackish water areas of central and southern Kuwait, except for a few isolated sites. However, nonpetroleum hydrocarbons, with ultraviolet-visible absorption characteristics and fluorescence characteristics typically associated with humic substances, were observed at a few sites in the brackish water fields.