Determination of Gold, Silver and Platinum-Group Elements in Geochemical Reference Materials by Direct Atomic Emission Spectral Analysis Using a Multichannel Analyser Recording Device

A procedure for the analysis of geochemical samples has been developed based on direct atomic-emission spectrometry for the determination of silver, gold and the platinum-group elements. Instrumentation comprised a DC arc emission two-jet plasmatron coupled to a diffraction spectrograph and multichannel analyser for recording emission spectra. Spectrum analysis used a comprehensive library of spectral lines for practically all elements excited using this emission source. The software programme for the automatic registration of spectra and subsequent data processing are described and results presented for a number of geochemical reference materials.     

高温高压改色处理Ⅰa型褐色钻石的光谱鉴定特征

Ⅱa型钻石的高温高压改色及褪色研究已开展了大量工作,然而对Ⅰa型Cape系列褐色钻石在高温高压处理条件下的行为尚不明确。为解析实验室钻石鉴定工作中遇到的黄色钻石颜色成因问题,本文选取了Ⅰa型Cape系列褐色钻石作为研究对象,进行高温高压改色处理实验,并对处理前后的样品的紫外可见吸收光谱、红外吸收光谱以及光致发光光谱等谱学特征进行对比分析。结果表明:经高温高压改色处理后,钻石颜色由灰褐色变为褐黄色,钻石的紫外可见吸收光谱、红外吸收光谱和光致发光光谱也发生了很大改变。经处理的褐色钻石,其紫外可见吸收光谱中除原有的415nm和477nm吸收外,还产生503.2nm吸收,同时550nm至短波的吸收增强,钻石因此由原来的灰褐色变为褐黄色;红外吸收光谱中,1498、1520、1547cm~(-1)三个峰变为一个以1498cm~(-1)为中心的吸收宽峰;光致发光光谱中,产生了明显的H3(503.2nm)以及H2(986.2nm)缺陷。本研究获得的光谱变化特征为准确鉴定高温高压改色处理的Cape型钻石提供了依据,也为更好地理解晶格中氮、氢等相关的格子缺陷在高温高压条件下的变化机理提供了实验数据和分析。     

同结线附近AbxAnxDiy系列硅酸盐熔体结构及其结晶相的光谱研究

通过高温熔融，对同结线附近一系列硅酸盐熔体进行淬冷或不同速度冷却，实验获得的样品经过显微拉曼光谱分析，对比研究了AbxAnxDiy系列熔体在不同结线附近熔体结构跨相区变化情况，以及析出晶体对相应熔体结构的继承特点，熔体结构单元相对含量，在相界线两侧有某种程度的突变，熔体结构的变化对熔体的粘度，密度影响不同，拉曼光谱检测显示，硅酸盐玻璃的结构对降温速度变化不敏感，晶体对其相应熔体结构的部分继承作用，可能意味着晶体生长单元与熔体结构单元密切相关。     

紫色“山仔濑石”的颜色成因及成矿机制研究

紫色“山仔濑石”为寿山石的一种，是一种由层状硅酸盐矿物组成的黏土质玉石。其表层风化为黄色，内部为紫色，属于图章石中较为稀少的颜色品种。本文采用常规的宝石显微镜对其外观特征进行详细观察；利用X射线粉晶衍射仪、显微激光拉曼光谱仪、扫描电子显微镜、激光剥蚀等离子质谱仪等对其矿物组成、化学成分、稀土元素特征及谱学特征进行测试；利用全岩化学分析、紫外-可见光分光光度计、SPSS分析模型对其颜色成因进行研究。结果发现紫色“山仔濑石”的主要矿物组成为伊利石，次要矿物为独居石、磷钡铝石、赤铁矿和重晶石；其稀土元素指示性数据呈现出轻稀土元素富集，重稀土元素亏损的现象，指示其矿物成因与还原的酸性热液蚀变有关；紫色“山仔濑石”的紫色色调深浅与伊利石中Mn含量高低呈现正相关性；紫色“山仔濑石”内主要矿物和次要矿物的种类、分布特征和形成温度的不同说明在成矿后期存在多期热液侵入，紫色“山仔濑石”的形成过程与寿山地区的成矿规律具有一致性。     

Isothermal compression of an eclogite from the Western Gneiss Region (Norway)

In the Western Gneiss Region in Norway, mafic eclogites form lenses within granitoid orthogneiss and contain the best record of the pressure and temperature evolution of this ultrahigh-pressure (UHP) terrane. Their exhumation from the UHP conditions has been extensively studied, but their prograde evolution has been rarely quantified although it represents a key constraint for the tectonic history of this area. This study focused on a well-preserved phengite-bearing eclogite sample from the Nordfjord region. The sample was investigated using phase-equilibrium modelling, trace-element analyses of garnet, trace- and major-element thermobarometry and quartz-in-garnet barometry by Raman spectroscopy. Inclusions in garnet core point to crystallization conditions in the amphibolite facies at 510–600°C and 11–16 kbar, whereas chemical zoning in garnet suggests growth during isothermal compression up to the peak pressure of 28 kbar at 600°C, followed by near-isobaric heating to 660–680°C. Near-isothermal decompression to 10–14 kbar is recorded in fine-grained clinopyroxene–amphibole–plagioclase symplectites. The absence of a temperature increase during compression seems incompatible with the classic view of crystallization along a geothermal gradient in a subduction zone and may question the tectonic significance of eclogite facies metamorphism. Two end-member tectonic scenarios are proposed to explain such an isothermal compression: Either (1) the mafic rocks were originally at depth within the lower crust and were consecutively buried along the isothermal portion of the subducting slab or (2) the mafic rocks recorded up to 14 kbar of tectonic overpressure at constant depth and temperature during the collisional stage of the orogeny.     

应用扫描电镜-红外与反射光谱研究海水灰色Akoya珍珠特异的矿化微结构特征

近年来海水灰色Akoya珍珠是珍珠类饰品的新宠,前期研究主要聚焦在对其海水属性、各结构单元的元素赋存特征、辐照处理及其鉴别方法等方面.本文借助紫外可见(UV-Vis)反射光谱仪、显微红外光谱仪、扫描电镜等技术,对具有白色内核的一类灰色珍珠的宝石学与其精细结构特征进行研究.结果表明:①在珍珠的珠核与珍珠层之间,基本存在厚...     

Quasars in the field of 88 Leonis

We present spectroscopically confirmed quasars in the 25 sq. degrees A1-field to a limiting magnitude of m_B = 18.0. Our estimate of the quasar density of 0.28 ± 0.11 objects per sq. degree based on the “complete” sample of A1-qusars is in agreement with the observed integral number-magnitude relation. However, we consider this value as still a lower limit of the quasar density in the A1-field due to the uncertainties during the colour based selection of objects, especially their brightness dependence, resulting in serious selection effects. Thus, the quasar density of the A1 survey may be underestimated up to 30% and does not contradict the recently estimated incompletness of the BQS survey.     

浙江方家山高岭土矿床中高岭石亚族矿物的研究

珍珠陶石、地开石和高岭石是高岭石亚族矿物的三种多型。其中高岭石最常见,地开石较少见,而珍珠陶石是十分罕见的多型。本文作者应用Ｘ射线衍射、红外光谱和醋酸钾夹层化合物的方法,研究了浙江方家山高岭石矿物特征。研究表明,用醋酸钾为夹带剂形成的珍珠陶石夹层化合物具有１４．０的特征衍射峰,经水分子取代后形成８．３５特征的珍珠陶石水合化合物,而高岭石仅部分形成７．３０水合夹层化合物。从而确定了方家山高岭土矿床是以高岭石为主含珍珠陶石的矿床,其珍珠陶石主要赋存于粗粒级的高岭土中。高岭石与珍珠陶石晶畴呈消长关系可能说明珍珠陶石是后期较强应力下由高岭石转变来的。     

基于红外光谱技术研究云南普朗斑岩铜矿的蚀变和矿化特征

近年来红外光谱技术作为一种绿色、快速、无损、精确探测矿物的技术手段而倍受关注,针对斑岩型矿床蚀变矿物高度叠加、蚀变分带界线不明显、细粒蚀变矿物多、黏土蚀变矿物多等特征,该技术在蚀变矿物识别和勘探信息解读等方面优势突出。本文应用红外光谱技术对云南普朗斑岩铜矿区钻孔ZK1801岩心进行矿物识别和蚀变分带划分的研究,识别出钾硅酸盐化带、绿帘石-绿泥石化带、绿泥石-伊利石化带、石英-伊利石化带和泥化带。研究表明:普朗铜矿整个钻孔的蚀变矿物主要有石英、钾长石、绢云母、绿泥石、绿帘石、高岭石、蒙脱石、伊利石等;根据矿化特征,发现铜矿体广泛赋存在钾硅酸盐化带和绿帘石-绿泥石化带中,与矿化关系密切的蚀变矿物"石英+钾长石+绢云母"和"绿帘石+绿泥石",可以作为普朗矿床勘查的标型蚀变矿物组合;研究区广泛发育的绢云母Al—OH波长随钻孔深度增加而逐渐从2210～2205nm减小到2202～2198nm, Al—OH波长2210～2205nm(长波绢云母)与矿化关系密切,可以作为普朗矿床勘查的指示信息。     

热红外反射光谱技术在石英含量评价中的应用

石英是热液矿床重要的找矿标志,也是影响页岩气储层可压裂性评价的关键性因素,目前主要利用X射线衍射方法和扫描电镜矿物定量分析方法进行实验室内石英定量分析。为满足野外钻井现场进行快速、大批量矿物定量分析的需求,本文以羌塘盆地泥岩、砂岩、砾岩、灰岩和白云岩等沉积岩样品为研究对象,应用热红外反射光谱技术和综合自动矿物岩石学(QEMSCAN)矿物定量分析技术,开展了石英热红外反射光谱含量评价研究。结果表明:石英在8625nm、12640nm和14450nm三个特征中心波长位置的相对深度(D_(8625)、D_(12640)、D_(14450))可以用来区分陆源碎屑岩和碳酸盐岩,当D_(8625)0.14或D_(12640)0.02或D_(14450)0.02时,样品岩性主要为陆源碎屑岩,否则主要为碳酸盐岩。此外,D_(8625)、D_(12640)、D_(14450)三个石英光谱特征参数均与石英含量具有高度的相关性,均可以利用最小二乘法构建石英含量评价模型。以拟合优度(R~2)和均方根误差(RMSE)两个指标评价三个模型的精度,其中根据D_(8625)参数建立的石英含量估算模型的拟合优度最大(R~2=0.9237),且均方根误差最小(RMSE=8.51),基于此认为D_(8625)石英光谱参数可以作为评价石英含量的最优光谱指标。本文基于热红外反射光谱技术建立的该种野外快速估算钻井中石英含量的方法,为热液矿床找矿勘查和页岩气勘探开发提供了借鉴和参考。