Petrographic and trace element analysis of uranium-rich tufa calcite, middle Miocene Barstow Formation, California, USA     

Jennifer M. Cole  E. Troy Rasbury†  Isabel P. Montañez‡  Vicki A. Pedone§  Antonio Lanzirotti¶  Gilbert N. Hanson† 《Sedimentology》2004,51(3):433-453

An integrated petrographic and spectroscopic (X‐ray diffraction, phosphor imaging and synchrotron X‐ray absorption spectroscopy) study of tufas from the Miocene Barstow Formation, California, relates sample morphology, mineralogy and geochemical composition. The tufas, composed mainly of calcite that formed at the interface between an ancient alkaline lake and ground or spring waters, have textures similar to those of microbially mediated terrestrial stromatolites and travertines. The tufas have elevated concentrations of a number of trace elements including Mn, Fe, Sr and U. Synchrotron X‐ray fluorescence analyses show that U concentrations can exceed 500 p.p.m. X‐ray absorption spectroscopy indicates that the U in these samples is incorporated as U(IV). It is suggested here that alkaline lake waters had a high U/Ca ratio and tufa calcite formed where groundwater or (possibly epithermal) springs brought in Ca and trace elements such as Sr. The rapid, and possibly microbially mediated, precipitation of calcite allowed for incorporation of high concentrations of trace metals as either structural substitutes or extremely fine‐scale inclusions.  相似文献   

Synchrotron radiation X-ray diffraction in situ study of fine-grained minerals in shock veins of Suizhou meteorite   总被引：2，自引：0，他引：2  

XIE Xiande  SHU Jinfu & CHEN Ming . Guangzhou Institute of Geochemistry  Chinese Academy of Sciences  Guangzhou  China  . Geophysical Laboratory  Carnegie Institution of Washington  Washington  DC    USA Correspondence should be addressed to Xie Xiande 《中国科学D辑(英文版)》2005,48(6)

The Suizhou meteorite is an L6chondrite,which fell on April15,1986in Dayanpo,12.5km in the southeast of Suizhou City,Hubei Province,China[1].This meteorite is shock-metamorphosed to shock stage3—4[2].A few thin shock melt veins of0.02—0.09mm in width were observed in this chondrite[1,2].Similar to many other L6chondrites[3—5],the Suizhou shock veins contain two assemblages of high-pressure minerals[2,6—8]:(i)the“coarse-grained”assemblage of ringwoodite+majorite+NaAlSi3O8-hollandite…  相似文献   

应用同步辐射微束X射线荧光光谱法研究单个大气PM2．5颗粒物的源特征   总被引：3，自引：0，他引：3  

李晓林岳伟生  刘江峰万天敏  张桂林李燕  黄宇营何伟 华魏 《岩矿测试》2006,25(3):206-210

将高灵敏度的同步辐射微束x射线荧光光谱分析方法与计算机模式识别技术相结合，用于上海市大气PM2.5，单颗粒物的源识别。分析了污染排放源的PM2.5，单颗粒物，结果表明，来自不同污染排放源的颗粒物具有不同的能谱特征。同时分析了环境空气监测样品PM2.5，单颗粒物，结果表明，在上海市中心区大气PM2.5，的污染源主要以机动车尾气为主，而在吴淞工业区大气PM2.5，的污染源主要以钢铁工业尘和燃煤烟尘为主。  相似文献   

方钠石的原位高压X射线研究     

李海建 秦善刘景  李晓东巫翔 《岩石矿物学杂志》2006,25(4):323-326

在室温下使用金刚石对顶砧（DAC）高压装置和同步辐射光源，对架状硅酸盐矿物方钠石进行了原位高压X射线衍射实验，最高压力达到17．4GPa。在研究的压力范围内观察到在3GPa左右方钠石发生了一次相变，且压力大于6．3GPa时，d222出现异常增大。对方钠石在高压下相变以及d222增大的原因进行了分析，认为方钠石结构中存在着充填大阳离子的多面体笼和孔道，高压下这些笼和孔道容易扭曲变形，从而造成结构的改变。  相似文献   

地球内部物质物性的原位高温高压研究:大体积压机与同步辐射源的结合   总被引：2，自引：1，他引：2  

王雁宾 《地学前缘》2006,13(2):1-36

大体积压机(large-volume press,简称为LVP)与金刚石对顶砧(diamond-anvil cell,简称为DAC)是两种相辅相成的、在高压研究中不可或缺的重要技术。大体积压机在温压范围上较金刚石对顶砧小,但它具有更加均匀的温压环境以及高于金刚石对顶砧几千以至百万倍的试样体积。这些特色使大体积压机成为精确测量试样整体物性和系统研究复杂材料系列的理想工具。在过去的20年里,高压和同步辐射技术方面的进展使大体积高压研究取得了革命性的突破。文中选择近期地学界的一些重要科研成果和技术突破作为例子,力图对同步辐射和大体积高压技术在高温高压研究中的近期进展作综合评述,最后简略讨论了LVP的发展前景。  相似文献   

西藏曲水县达布斑岩型铜钼矿床金属沉淀机制探讨   总被引：6，自引：2，他引：4  

王艺云  唐菊兴  郑文宝  段吉琳  宋俊龙  杨超 《矿床地质》2015,34(1):81-97

西藏曲水县达布斑岩型铜钼矿床位于冈底斯成矿带中东段,其矿化体主要产于含矿斑岩体与围岩的内外接触带中。文章以矿石内Cu、Mo矿化石英脉中的流体包裹体为研究对象,探讨了成矿金属沉淀的机制。通过详细的显微镜下鉴定,发现Cu、Mo矿化阶段的流体包裹体类型均以L型为主,但Cu矿化阶段的V型包裹体明显较Mo矿化阶段多,而S型包裹体较少。Cu、Mo矿化石英脉中,常见L型、V型、S型流体包裹体共存的现象,且它们的均一温度范围非常接近,说明成矿流体经历了不混溶作用,使得高盐度流体与低密度气相流体发生分离。单个流体包裹体激光拉曼光谱测试显示,在Cu、Mo矿化阶段的气相包裹体中均检测到CO2的特征峰和H2O峰,而在Mo矿化阶段的气相包裹体仅检测到CH4特征峰,说明Mo矿化阶段的流体的相对还原性更强;同时,检测到硬石膏、赤铁矿、磁铁矿、黄铜矿、黄铁矿等子矿物,但硬石膏、赤铁矿、磁铁矿主要分布于Cu矿化阶段,说明Cu矿化阶段的流体氧化性相对较强。对单个流体包裹体进行同步辐射X射线荧光分析(SR-RXF)显示,Cu、Au等金属主要富集于流体包裹体气相中,表明Cu、Au元素可能是气相运移。对Cu、Mo硫化物沉淀的一系列化学反应研究表明,呈氧化态以及酸度低(HCl浓度低,即偏中性)的流体会促进黄铜矿饱和;活性较高的H2S和略呈还原性的流体有利于辉钼矿的沉淀。综合分析认为,铜矿化与偏中性、结晶分异程度相对较低的花岗闪长斑岩关系密切,而钼矿化与酸性、结晶分异程度相对较高的花岗斑岩关系密切。  相似文献   

同步辐射加速器X荧光分析技术在极地环境研究中的应用   总被引：1，自引：2，他引：1       下载免费PDF全文

谢周清  孙立广  程邦波  张莉  黄宇营 《极地研究》2004,16(2):99-105

本文简要介绍了同步辐射器X荧光(SRXRF)技术的分析原理和特点。概述了该技术在极地环境研究中的应用,并对其发展前景进行了展望。  相似文献   

Galactic magnetic turbulence from radio data     

Marco Regis 《Astroparticle Physics》2011,35(4):170-176

Fluctuations in the Galactic synchrotron emission can be traced by the angular power spectrum of radio maps at low multipoles. At frequencies below few GHz, large-scale anisotropies are mainly induced by magnetic field turbulence, since non-thermal electrons radiating at these frequencies are uniformly distributed over the scales of magnetic field inhomogeneities. By performing an analysis of five radio maps, we extract constraints on turbulence spectral index and halo scale. Results favour a power spectrum significantly flatter than for 3D Kolmogorov-like turbulence, and a thin halo. This can be interpreted as an indication supporting non-conventional models of propagation of cosmic-ray particles in the Galaxy, or as a suggestion of a spectral-index break in the observed magnetic turbulence power spectrum.  相似文献   

年轮化学示踪技术及在重现矿区重金属污染历史中的应用     

雷梅  郭立新  张山岭 《地理科学进展》2011,30(1):114-120

矿区自然分布的树木从环境中吸收重金属元素,并在形成层发育过程中将重金属元素储存在年轮中,通过分析年轮中重金属元素含量的变化特征,可以半定量判定不同污染途径对年轮中重金属元素的贡献率,进而重现矿区环境变迁历史.本文综述了国内外年轮化学在环境污染分析中的应用案例,针对影响年轮化学分析精度的各种环境因素,结合矿区污染特征,探...  相似文献   

BL Lac objects in the synchrotron proton blazar model     

A. Mücke  R. J. Protheroe  R. Engel  J. P. Rachen  T. Stanev 《Astroparticle Physics》2003,18(6):593-613

We calculate the spectral energy distribution (SED) of electromagnetic radiation and the spectrum of high-energy neutrinos from BL Lac objects in the context of the synchrotron proton blazar model. In this model, the high-energy hump of the SED is due to accelerated protons, while most of the low-energy hump is due to synchrotron radiation by co-accelerated electrons. To accelerate protons to sufficiently high energies to produce the high-energy hump, rather high magnetic fields are required. Assuming reasonable emission region volumes and Doppler factors, we then find that in low-frequency peaked BL Lacs (LBLs), which have higher luminosities than high-frequency peaked BL Lacs (HBLs), there is a significant contribution to the high-frequency hump of the SED from pion photoproduction and subsequent cascading, including synchrotron radiation by muons. In contrast, in HBLs we find that the high-frequency hump of the SED is dominated by proton synchrotron radiation. We are able to model the SED of typical LBLs and HBLs, and to model the famous 1997 flare of Markarian 501. We also calculate the expected neutrino output of typical BL Lac objects, and estimate the diffuse neutrino intensity due to all BL Lacs. Because pion photoproduction is inefficient in HBLs, as protons lose energy predominantly by synchrotron radiation, the contribution of LBLs dominates the diffuse neutrino intensity. We suggest that nearby LBLs may well be observable with future high-sensitivity TeV γ-ray telescopes.  相似文献