蒸馏法富集纯化Os实验条件研究及其在负离子热电离质谱测量中的应用

微蒸馏是富集纯化Os的一项重要化学前处理技术,提高Os回收率对提高Os的负离子热电离质谱(NTIMS)测量精度尤为重要。在微蒸馏过程中,蒸馏温度、吸收液体积、蒸馏时间等对Os回收率具有重要影响,但目前微蒸馏的实验条件不够明确,导致Os回收率不稳定,影响NTIMS测量精度,易增加所得Re-Os年龄误差。本文以自制的含Os溶液为对象,以ICP-MS为测量手段,对微蒸馏过程中多种实验条件对Os回收率的影响进行深入研究,以期获得最佳微蒸馏实验条件,满足后续NTIMS对Os信号强度的测量要求。结果表明:在溶液蒸干温度为120℃并保持15 min,微蒸馏温度为80℃,氢溴酸吸收液体积为15μL,微蒸馏时间为2 h的条件下,获得Os回收率为80%~90%,能够满足多种地质样品尤其是中酸性岩浆岩、热液硫化物等pg级地质样品的NTIMS测量要求,在保证Os信号强度的情况下提高了分析效率。     

沥青样品铼-锇同位素分析溶解实验研究

沥青样品中Re、Os含量较低,且组成复杂,因含有大量有机质,在溶样过程中会释放大量CO2,需要大量氧化剂。控制样品称样量和氧化剂比例、用量对保证Os的回收率以及测量信号的稳定性非常重要。本文根据沥青样品组成特点改进了Re-Os同位素分析技术方法,称样量由原来的0.2 g增加到0.4 g,氧化剂由原来的3 mLHCl、6 mL HNO3改为3 mL HCl、4 mL HNO3、3 mL H2O2,改进的方法所得到Os的信号强度提高了大约2倍。考察了改变溶剂组成对不同称样量沥青的氧化效果,研究了氧化剂中加入H2O2对不同称样量沥青样品溶解效果,以及对Os的回收率和仪器测量信号强度的影响程度。采用2 mL HCl、5 mL HNO3、2 mL H2O2作为氧化剂,Carius管高温密闭溶样,直接蒸馏法或传统蒸馏法分离富集Os,丙酮萃取法分离纯化Re,用电感耦合等离子体质谱法(ICP-MS)对采自云南某铅锌矿床的沥青样品Re-Os同位素进行分析测定。沥青的Re-Os同位素等时线年龄为(60±2)Ma(MSWD=2.5,n=7),初始187Os/188Os值为4.36±0.14,表明该沥青样品中Re-Os同位素体系的封闭性较好,而且物质来源为典型的壳源性质。建立的方法能够用于沥青年龄厘定与来源示踪方面的研究。     

两种质谱仪在辉钼矿铼-锇年龄测定中的应用比较

对同一地区但Re、Os含量不同的一组辉钼矿样品,分别采用电感耦合等离子体质谱(ICP-MS)和负离子热表面电离质谱(NTIMS)对其Re-Os年龄进行了测定比较。结果表明,该组样品的平均Re-Os模式年龄分别为(138.3±4.0)Ma和(141.0±3.6)Ma(2σ,n=9),采用ISOPLOT软件的模式1进行等时线计算,得到等时线年龄分别为(138.6±2.9)Ma(2σ,n=9)和(141.6±1.9)Ma(2σ,n=9),两者在目前水平下的误差范围内基本一致。另外,分别采用ICP-MS和NTIMS对辉钼矿Re-Os年龄国家一级标准物质GBW04435和GBW04436进行了测定,所得的结果吻合也较好。     

蒸馏分离-电感耦合等离子体质谱法测定地球化学样品中痕量钌和锇

建立了蒸馏分离-电感耦合等离子体质谱法测定地球化学样品中痕量钌和锇的分析方法。进行了蒸馏温度和时间、氧化剂、吸收液等条件的选择,消除了等离子体质谱法测定钌和锇的干扰。样品用过氧化钠熔融,酸化后以高锰酸钾-过硫酸钾-氯化钠作为同时蒸馏钌和锇的氧化剂,采用20 mL 50 g/L水合肼溶液同时吸收从混合物中分离出来的痕量钌和锇,用电感耦合等离子体质谱法测定。方法的检出限Ru为0.020 ng/g,Os为0.015 ng/g;方法加标回收率Ru为94.0%~102.7%,Os为96.0%~102.4%;精密度为4.72%~9.58%(n=12)。方法经国家一级标准物质验证,钌和锇的测定结果与标准值相符。     

安徽省金寨县沙坪沟钼矿中贵重分散元素铼的分析

采用Na2O2-CaO混合熔炉,达到完全分解辉钼矿和其它难溶矿的目的,干扰元素经两次沉淀分离消除,利用高铼酸根对碲酸还原产生催化极谱波,进行碲加入量和和干扰元素的试验,采用H2SO4-Na2SO4-Te底液催化极谱法,在JP-2D极谱仪上中辉钼矿痕量的铼,收到满意效果。解决了地勘一线实验室无ICP-MS等大型设备测定辉钼矿中分散元素铼     

含辉钼矿全岩样品Re-Os同位素定年研究:在北京大庄科钼矿床中的应用

采用硝酸在比色管中对辉钼矿样品中Re含量进行初测的方法,测得辉钼矿标准样品JDC Re含量与推荐值在误差范围内基本一致,与传统的Carius管法相比,该方法具有简便快速的特点。传统的辉钼矿Re-Os同位素定年分析对象为辉钼矿单矿物,根据所测得的187Re/187Os值获得辉钼矿的Re-Os年龄,Re、Os在辉钼矿中大量富集,而在硅酸盐矿物中几乎没有,探索性地对含有辉钼矿的全岩样品进行Re-Os同位素定年,虽然所得Re、Os含量偏低,但187Re/187Os值不会变。该方法省去了选样过程花费的大量时间,避免了选样过程中可能造成的交叉污染。采用同位素稀释Carius管逆王水法探索性地对北京大庄科钼矿床中含辉钼矿全岩样品进行Re-Os同位素年龄测定,获得了(137.6±3.7)Ma精确的等时线年龄,与挑选出辉钼矿单矿物样品的Re-Os同位素等时线年龄(136.8±2.6)Ma吻合较好,直接厘定了大庄科钼矿的成矿时代。该年龄与矿区汉家川石英二长岩锆石U-Pb年龄一致,表明大庄科钼矿的形成与汉家川石英二长岩关系较为密切,为中国东部第二期大规模成矿作用的产物,形成于中国东部岩石圈伸展环境。     

Carius管直接蒸馏快速分离锇方法的改进

蒸馏法是Re-Os同位素测量体系从基质中分离Os的一种快捷方法,但装置繁琐,清洗工作量大,已成为限制其应用的瓶颈。文章对Carius管传统蒸馏装置进行了改进,利用橡胶滴头代替硅胶管和玻璃堵头自制Carius管直接蒸馏接口装置,简化了气体进出口管路,使用电蒸笼代替电热套,对蒸馏时间、样品溶液稀释倍数和吸收液体积等蒸馏条件进行了优化。改进后的装置升温速度、稳定性和简便性得到提高,简化了实验器皿,有利于降低空白,实现在较小操作空间内大批量样品的同时处理。Carius管直接蒸馏实验结果表明,Os的回收率可达86.7%～95.2%。在长时间(2 h)蒸馏条件下,Os回收率比传统蒸馏瓶法高约41%。针对不同样品类型和测试仪器,可选择相应的蒸馏条件,有效压缩了样品处理时间,提高了测量计数。对Re-Os定年标准物质GBW 04436(JDC)测定5次的模式年龄为(139.5±1.9)Ma～(142.0±2.1)Ma,标准物质GBW 04435(HLP)测定2次的模式年龄为(220±3.3)Ma～(223.0±3.2)Ma,分别与标准值(139.6±3.8)Ma和(221.4±5.6)Ma在不确定度范围内一致。改进后的Carius管直接蒸馏装置已应用于日常样品处理。     

Re-Os同位素稀释N-TIMS测定计算方法

为了更好地实现Re-Os同位素实验室之间数据比对,本实验室在了解国内外部分实验室的数据处理方法的基础上,提出了本实验室的N-TIMS Re、Os同位素计算方法。本文所涉及到的Re、Os同位素计算方法包括氧同位素干扰校正、Re同位素比值和含量计算、Os同位素测定质量分馏校正方法、三峰法和全峰法Os同位素比值和含量计算、测定结果的不确定度、Isoplot作图基本参数介绍和相关系数Rho的计算。对于辉钼矿和普通Os信号弱(~(187)Os/~(188)Os2000)的样品适合采用三峰法计算Os同位素比值,普通Os信号强(~(187)Os/~(188)Os2000)的样品应该采用全峰法计算同位素比值。在全峰法计算中,按照指数分馏规律以迭代计算方式校正Os同位素比值的质量分馏,采用5iso方法进行样品中Os和稀释剂中Os的摩尔比(N_(5iso)/S)_(Os)的计算。     

~(186)锇和~(188)锇双同位素稀释法在辉钼矿铼-锇测年中的应用

以经过负离子热表面电离质谱仪准确标定的1 86Os和1 88Os双同位素作为稀释剂 ,利用1 86Os和1 88Os计算1 87Os的含量 ,能有效地减少用等离子体质谱仪测定1 87Os时由于仪器本身的不稳定性及质量歧视效应所产生的误差 ,使测量准确度比用单同位素作为稀释剂有明显提高。方法应用于辉钼矿Re -Os年龄标准参考物及样品的测定 ,结果与参考值一致 ,5份试样测定的RSD <3%。     

黄铁矿 Re-Os 同位素定年化学前处理若干条件初探

对黄铁矿 Re-Os 同位素定年化学前处理过程中的溶样温度、溶样酸介质及溶样时间进行了条件实验.温度实验结果表明,溶样温度对 Re 的测定结果影响不大,而对 Os 的测定结果影响较明显.溶样温度在120~220℃之间时,无论是 HNO3还是逆王水溶样, Re 含量在误差范围内都是一致的,但在120℃、150℃时, Os 的含量偏离真实值,可能是样品和稀释剂中的 Os 同位素并未完全达到平衡,在180℃、200℃和220℃时, Os 的含量基本一致且接近真实值.溶样酸介质实验表明, HNO3和逆王水溶样对 Re 的测定影响不大,而对 Os 的测定影响较明显.无论是用 HNO3还是逆王水溶样,在不同温度下所得到的 Re 含量是一致的,而在120℃、150℃时,逆王水溶样较 HNO3溶样所得到的 Os 含量更加接近真实值,180℃、200℃和220℃时,两种酸介质溶样得到的 Os 含量基本一致且接近真实值.用逆王水在200℃时溶样,时间为5 h、8 h、12 h、18 h所得到的 Re、187Os 含量基本一致,说明较高温度下在较短的时间内便能达到较好的溶样效果.Fe3+浓度对Re 的阴离子交换效率实验表明, Re 的回收率随着 Fe3+浓度的不断升高而逐渐下降.当黄铁矿取样量为3 g时,上柱体积控制在40 mL 左右可获得较高的 Re 回收率     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

Inter-regional correlation of transgressions and regressions in the Cretaceous period

Well investigated platforms have been selected in each continent, and the history of Cretaceous transgressions and regressions there is concisely reviewed from the available evidence. The factual records have been summarized into a diagram and the timing of the events correlated between distant as well as adjoining areas.On a global scale, major transgressions were stepwise enlarged in space and time from the Neocomian, via Aptian-Albian, to the Late Cretaceous, and the post-Cretaceous regression was very remarkable. Minor cycles of transgression-regression were not always synchronous between different areas. Some of them were, however, nearly synchronous between the areas facing the same ocean.Tectono-eustasy may have been the main cause of the phenomena of transgression-regression, but certain kinds of other tectonic movements which affected even the so-called stable platforms were also responsible for the phenomena. The combined effects of various causes may have been unusual in the Cretaceous, since it was a period of global tectonic activity. The slowing down of this activity followed by readjustments may have been the cause of the global regression at the end of the Cretaceous.     

The lamprophyres of Afyon stratovolcano,western Anatolia,Turkey: description and genesis

The Afyon stratovolcano exhibits lamprophyric rocks, emplaced as hydrovolcanic products, aphanitic lava flows and dyke intrusions, during the final stages of volcanic activity. Most of the Afyon volcanics belong to the silica-saturated alkaline suite, as potassic trachyandesites and trachytes, while the products of the latest activity are lamproitic lamprophyres (jumillite, orendite, verite, fitztroyite) and alkaline lamprophyres (campto-sannaite, sannaite, hyalo-monchiquite, analcime–monchiquite). Afyon lamprophyres exhibit LILE and Zr enrichments, related to mantle metasomatism.     

METAMORPHIC PETROLOGY

正20140751 Guo Xincheng(Geological Party,BGMRED of Xinjiang,Changji 831100,China);Zheng Yuzhuang Determination and Geological Significance of the Mesoarchean Craton in Western Kunlun Mountains,Xinjiang,China(Geological Review,ISSN0371-5736,CN11-1952/P,59(3),2013,p.401-412,8     

GEOCHEMICAL EXPLORATION

正20141058 Chen Ling(Key Laboratory of Mathematical Geology of Sichuan Province,Chengdu University of Technology,Chengdu610059,China);Guo Ke Study of Geochemical Ore-Forming Anomaly Identification Based on the Theory of Blind Source Separation(Geosci-     

SEISMIC GEOLOGY

正20141334 Chen Kun(Institute of Geophysics,China Earthquake Administration,Beijing100081,China);Yu Yanxiang Shakemap of Peak Ground Acceleration with Bias Correction for the Lushan,Sichuan Earthquake on April20,2013(Seismology and Geology,ISSN0253-4967,CN11-2192/P,35(3),2013,p.627-633,2 illus.,1 table,9 refs.)Key words:great earthquakes,Sichuan Province     

HISTORICAL GEOLOGY & STRATIGRAPHY

正20141624 Cai Xiongfei(Key Laboratory of Geobiology and Environmental Geology,Ministry of Education,China University of Geosciences,Wuhan 430074,China);Yang Jie A Restudy of the Upper Sinian Zhengmuguan and Tuerkeng Formations in the Helan Mountains(Journal of Stratigraphy,ISSN0253-4959CN32-1187/P,37(3),2013,p.377-386,5 illus.,2 tables,10 refs.)     

PALEONTOLOGY

正20142263Lü Shaojun(Geological Survey of Jiangxi Province,Nanchang 330030,China)Early-Middle Permian Biostratigraphical Characteristics in Qiangduo Area,Tibet(Resources SurveyEnvironment,ISSN1671-4814,CN32-1640/N,34(4),2013,p.221-227,2illus.,2tables,22refs.)Key words:biostratigraphy,Lower Permian,Middle Permian,Tibet     

MATHEMATICAL GEOLOGY

正20142560Hu Hongxia(Regional Geological and Mineral Resources Survey of Jilin Province,Changchun 130022,China);Dai Lixia Application of GIS Map Projection Transformation in Geological Work(Jilin Geology,ISSN1001-2427,CN22-1099/P,32(4),2013,p.160-163,4illus.,2refs.)     

GEOCHEMISTRY

正20140692 Duo Tianhui(No.402 Geological Team,Exploration of Geology and Mineral Resources of Sichuan Authority,Chengdu611730,China);Wang Yongli Computer Simulation of Neptunium Existing Forms in the Groundwater(Computing Techniques for Geophysical and Geochemical Exploration,ISSN1001-1749,CN51-1242/P,35(3),