Nondestructive rare earth element imaging of fish teeth from deep‐sea sediments

X‐ray fluorescence computed tomography is an emerging imaging modality that allows for the nondestructive reconstruction of the internal distribution of elements within a sample. The common use of X‐ray excitation energy (up to approximately 20 keV) has necessitated the use of l ‐shell fluorescence for heavy elements. In this study, based on high energy X‐ray at BL13W1 of the Shanghai Synchrotron Radiation Facility, we employed high‐energy excitation for tomographic imaging of the heavy metals (rare earth elements) in fish teeth from deep‐sea sediments on the micrometer scale using K‐shell X‐ray fluorescence. The virtual cross‐sectional distribution of La, Ce, Pm, Pr, Nd, and Sm were obtained, thereby providing a feasible approach for analyzing the enrichment mechanism of rare earth elements. Copyright © 2015 John Wiley & Sons, Ltd.     

高分辨率光谱学揭示东太平洋CC区结核金属赋存状态及富集机制

赤道东太平洋克拉里昂-克利珀顿带（CCZ）是全球最有经济潜力的结核成矿带,存在巨量的Mn,Co,Ni,Cu,Zn和Li金属资源。前人对CCZ结核的研究偏重化学、矿物学分析,对结核显微纹层、金属赋存状态缺少高分辨率光谱学分析,制约了对金属富集机制的理解。采用扫描电镜（SEM）、X射线衍射仪(XRD)、微区X射线荧光面扫(XRF)、激光剥蚀电感耦合多接受质谱仪(LA-ICP-MS)对克拉里昂-克利珀顿带结核的显微纹层展开高分辨率分析,结果表明结核是由水成层韵律和成岩层韵律交替形成的。水成层由水羟锰矿组成,具有低的Mn/Fe,Li,Ni,Cu,Zn和高的Co,Fe,Ti,V含量,推测受铁的羟基氧化物库仑力吸附作用和高价锰氧化物八面体的表面氧化作用,水成层吸纳高含量Co,Ti和V元素。成岩层矿物组分主要是水钠锰矿,吸纳高含量的Li,Ni,Cu和Zn,其吸纳能力随Mn/Fe升高而提高,当Mn/Fe>8达到峰值。笔者认为结核生长环境中的Mn和Fe相对通量控制了结核的矿物类型和化学组分,而金属通量也可能影响了结核的金属成分。     

深海富钴结核微区X射线荧光光谱分析和数据挖掘

西太平洋富钴结核是近年来新发现的海底固体矿产资源,富含Mn,Fe,Co,Ni和Cu等多种关键金属元素。富钴结核是一种非均质的地球化学和矿物学集合体,粒径约6 cm的结核在生长过程中记录了数千万年的海洋沉积历史,亟需高分辨率的分析技术揭示古海洋环境信息。采用微区X射线荧光光谱仪（μ-XRF）,对C3BC1704富钴结核开展多元素面扫描,获得了原位高分辨率多元素的信号强度数据,评价了μ-XRF技术在富钴结核中的应用质量。元素信号谱峰特征和数据频谱分布结果显示,富钴结核中Mn,Fe,Ti,Co,Ca和Ni等元素信号强度敏感,数据呈现相对较好的正态分布特征,可用于定量或半定量分析;Si,Cu和Al等元素信号较弱,数据呈现左偏的正态分布特征,建议相关数据仅作参考。μ-XRF获得的数据量庞大且彼此独立,本研究将不同元素连接成彼此关联的多维矩阵,实现了数据的位置信息和特征元素之间的数学运算和筛选,了解了金属元素的分布和变化特征,揭示了富钴结核生长过程的环境变化。结果显示,Mn和Fe等元素在生长层中波动剧烈,金属元素在富钴结核中的分布极不均匀,显示出多成因类型的交替微层和7个大的生长周期旋回。C3BC1704富钴结核主体暴露在海水中,金属元素主要来自海水,化学组成指示为典型的水成成因。进一步定量分析结果显示,Mn,Cu和Ni等元素含量从内部向外围呈现同步降低的趋势,Fe,Ti和Co等元素含量则呈现同步升高的趋势,这些特征指示早期偏向于成岩富集环境,晚期则以水成富集为主。富钴结核金属元素的分布和变化特征,清晰呈现了富钴结核的生长结构,揭示了富钴结核生长过程的环境变化,有利于富钴结核的成矿模型的构建。     

中国陆架沉积物标准物质研制

报道了我国研制的2个大陆架沉积物标准物质MS-E1,MS-S1。MS-E1和MS-S1的原样分别取自东海和南海。样品经风干、破碎,球磨制备成均匀的粉体样品。均匀性采用高精度的X射线荧光光谱法检验。样品的化学组分采用国内外多实验室协同分析方式定值,有7个国内实验室和9个国外实验室参加了合作分析。测试组分均为67个,分别有43和42个组分定为保证值,8和9个组分作为参考值。全组分百分总和分别为99.8%和99.6%。经2年多的试用,2个标准物质已于2005年被国家计量部门批准为国家一级标准物质,其编号分别为:GBW07335和GBW07336。     

Formation,growth and dissociation of clathrate hydrate crystals in liquid water in contact with a hydrophobic hydrate-forming liquid

Variations in macroscopic morphology of hydrate crystals formed to intervene between a liquid-water phase and a liquid-hydrochlorofluorocarbon (HCFC) phase have been observed. The HCFC used was R-141b (CH₃CCl₂F) which is known to form a structure II clathrate hydrate at temperatures lower than 281.5 K, the triple liquid-water/hydrate/liquid-R-141b equilibrium temperature T_tri, under the atmospheric pressure. Each experiment was commenced by immersing an R-141b drop in a quiescent pool of water, which was either an ordinary pure water having no prior contact with R-141b or a water presaturated with R-141b at a temperature higher than T_tri. With presaturated water held at a large subcooling (∼6.5 K) below T_tri, we have distinguished two stages of hydrate-crystal growth, which are greatly different from each other both in crystal-growth morphology and in time span. The primary stage is characterized by lateral growth of a thin, fine-grained polycrystalline layer along the surface of each R-141b drop for a period of several tens of seconds. The secondary stage begins typically with a delay of some 10 min and lasts for a few tens of hours; it is characterized by radial growth of plate-like crystals standing upright on the outer surface of the drop-enclosing hydrate shell formed in the primary stage, thereby protruding into the liquid-water phase. A subsequent temperature rise within the range below T_tri causes a dissolution of plate-like crystals, leaving the hydrate shell apparently unchanged. The second stage is never observable with pure water and/or at a small subcooling (≲2 K). A qualitative interpretation of these observations is presented.     

Scaling of the near-wall layer beneath turbulent separated flow

This paper is a continuation of an earlier paper [P.E. Hancock, Velocity scales in the near-wall layer beneath reattaching turbulent separated and boundary layer flows, Eur. J. Mech. B Fluids 24 (2005) 425–438] in which it is proposed that each Reynolds stress has its own velocity scale. Two of these, $u_{\tau }^{\prime }$ and $w_{\tau }^{\prime }$, are directly related by definition to the r.m.s. of the wall-shear-stress fluctuations (${\tau }_x$ and ${\tau }_z$) in the streamwise and transverse directions. They are also velocity scales for the true dissipation of the turbulent kinetic energy and the Kolmogorov velocity and length scales at the surface. From asymptotic considerations it is shown that the other two scales are related to averages involving instantaneous gradients of wall-shear-stress fluctuations. The measurements, made using pulsed-wire anemometry into the viscous sublayer, show that $u_{\tau }^{\prime }$ and $w_{\tau }^{\prime }$ are also the velocity scales for the respective streamwise and transverse fourth-order velocity moments, together with the viscous velocity scale ($\nu /y$). Normalised, the fourth-order moments show an inner-layer-like behaviour independent of both position and direction, like that seen in the second-order moments [P.E. Hancock, Velocity scales in the near-wall layer beneath reattaching turbulent separated and boundary layer flows, Eur. J. Mech. B Fluids 24 (2005) 425–438]. However, not surprisingly, the third order moments exhibit an effect of mean shear, seen in the skewing of the probability distributions. Though not measured directly, the measurements imply the behaviour of the averaged products of fluctuations in wall-shear-stress and wall-pressure-gradient ($\overline{{\tau }_x\partial p/\partial x}$ and $\overline{{\tau }_z\partial p/\partial z}$). Normalised, they also are independent of position and direction. Some of the results presented apply more generally to the near-wall region beneath turbulent flow.     

西南印度洋超慢速扩张脊海底热液硫化物中金银矿物的富集特征及富集机制研究

通过电感耦合等离子体光谱仪(ICP-AES)以及扫描电镜等手段对超慢速扩张的西南印度洋中脊热液区的3个硫化物样品的金银含量及其赋存状态进行了研究。通过ICP-AES测定金银含量,结果发现3个样品均有Au和Ag富集的现象。通过能谱-扫描电镜联用(SEM/EDS),在三个样品中发现了大量的金银矿物。其中S27-4中,主要以不规则粒状的银金矿和自然金的形式赋存于硫化物中或者晶粒之间,而S35-22中,则发现了大量的银矿物和部分银金矿。能谱分析表明银矿物中常伴随有一定量的卤族元素,推测以卤化银的形式存在,银金矿除了以粒间金赋存还可以呈乳滴状被吸附在黄铁矿表面或者晶棱上,推测与黄铁矿表面缺陷有关。S35-17样品中银金矿是唯一被发现的矿物相,以包体金、吸附金和间隙金形式赋存。由于不同样品中,银金矿的摩尔比有所不同,指示形成环境有所不同。研究结果表明,S27-4的成矿流体中,Ag主要以AgCl-₂络合物迁移,Au经历了以AuCl-₂络合物到AuHS0络合物为主的转变,指示了其温度从中高温到中低温的变化过程,说明了传导冷却在这个变化过程中有重要作用。S35-22中金银矿物的形成也具有类似的富集机制,但S35-22中卤化银的形成显示了早期高温高氯度的流体环境。而黑烟囱样品S35-17中银金矿的形成则与热液流体与海水的混合作用有密切关系。     

Frobenius integrable decompositions for high-order nonlinear evolution equations

Two classes of nonlinear evolution equations are obtained, which possess Frobenius integrable decompositions. The resulting solitons are illustrated to describe the solution phenomena.     

福州盆地第四纪钻孔XRF连续扫描的元素特征及沉积相指示意义

对福州盆地河口地区一个39 m钻孔岩芯进行X-Ray Fluorescence(XRF)扫描,通过XRF元素连续扫描结果探讨福州盆地海陆交互地层在不同沉积单元中各元素的变化特征及其沉积相指示意义。钻孔岩芯从晚更新世晚期至全新世共经历了5个沉积阶段：湖泊相—河流冲积相—淤泥质滨海潮滩相—河口潮滩相—河流冲积相。XRF扫描结果表明：元素Co, Fe, Ti, Si及其与Rb的比值受到沉积物粒度影响较大,对陆相(河流相)和海相(潮滩相)中粒度特征相近的层位进行了元素均值统计显示,近岸河口湾海相沉积物中的Ca, Ti, Mn, Fe, Co等元素是陆相地层中的3～10倍,Si元素则在陆相层中相对富集。说明除了粒度因素,海-陆沉积环境的变化对元素的富集也起到了重要作用。Ca,Ti,Mn,Fe,Co等元素是较好的海相沉积指示元素,而Si则是较好的陆相沉积指示元素,K,Rb,Sr对陆相沉积具有一定的指示意义。研究结果表明XRF元素连续扫描可以识别沉积物的元素变化细节,并根据元素的强度变化进一步判断沉积相,可以作为沉积相划分的重要辅助手段。该研究为XRF连续扫描方法在海陆交互带的应用提供了实例。