Pb-Isotope Analyses of USGS Reference Materials

Conventional corrections for thermal ionisation mass spectrometer (TIMS) induced Pb-isotopic fractionation often result in a loss of accuracy because the commonly employed pure Pb reference materials (NIST SRM 981, 982) frequently exhibit markedly different fractionation behaviour to real geological samples. As a result, these SRMs are inappropriate for comparison and/or correction of inter-operator/ laboratory biases. A matrix-matched reference material would be preferable but, as yet, no systematic study has approached this problem. Here we present high quality Pb-isotope ratio determinations, obtained using a double spike procedure, for six USGS reference materials in an attempt to address this deficiency. Our data suggest that most of these rocks could be used as isotopic reference materials comparable, in terms of uncertainty, to the NIST SRMs. However, significant differences in isotopic composition exist between first (e.g. BCR-1) and second (e.g. BCR-2) generation samples. The cause of these differences remains unclear but has significant implications for their use as trace element reference materials.     

Silver Content of Some USGS Standard Rocks

The state of the art for silver determination in silicate rocks is discussed on the basis of available data on geostandards. A neutron activation procedure for silver in rocks is briefly described, and data on seven new USGS standard rocks are presented and discussed.     

Calcium Isotopic Compositions of Sixteen USGS Reference Materials

Calcium isotopic compositions of sixteen Ca‐bearing USGS geological reference materials including igneous and sedimentary rocks are reported. Calcium isotopic compositions were determined in two laboratories (GPMR, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan; and CIG, Centre for Isotope Geochemistry, University of California, Berkeley) using the ⁴²Ca‐⁴⁸Ca double‐spike technique by thermal ionisation mass spectrometry. As opposed to common cation exchange resin, a micro‐column filled with Ca‐selective resin (DGA resin) was used in order to achieve high recovery (> 96%) and efficient separation of Ca from the sample matrix. The intermediate measurement precision was evaluated at 0.14‰ (2s) for δ^44/40Ca_SRM915a at GPMR, based on replicate measurements of pure Ca reference material NIST SRM 915a, NIST SRM 915b and seawater. Overall, the measurement uncertainties in both laboratories were better than 0.15‰ at the 2s level. Result validation was carried out for all available data sets. The Ca isotopic compositions of USGS reference materials are not only in agreement between GPMR and CIG, but also in agreement with previously published data within quoted uncertainties. The comprehensive data set reported in this study serves as a reference for both quality assurance and interlaboratory comparison of high precision Ca isotopic study.     

Trace Metal Speciation of USGS Reference Sample MAG-I

The USGS reference sample marine mud MAG-1 has been subjected to a sequential extraction procedure designed to partition the constituent trace metals into five fractions: I-exchangeable; II- bound to carbonates; III-bound to Fe-Mn oxides; IV- bound to organic matter; V- residual. The analytical approach involved successive chemical extractions and the subsequent determination of trace metal concentrations (Co, Cu, Ni, Pb, Zn; Fe, Mn) in the leachates by atomic absorption spectrophotometry. The chemical speciation results obtained on four replicate sub-samples demonstrate that the coefficients of variation for metal concentrations in the individual fractions are generally better than + 10%. Comparison with published values for total trace metal concentrations in the MAG-1 sample suggests that the overall accuracy of the chemical extraction procedure is satisfactory.     

美国地质调查局工作重点变化分析与思考

美国地质调查局(USGS)不同时期财政预算拨款数额和结构的变化,不仅反映其工作重点的变化,更深层次是反映出 USGS 围绕国家重大需求做出的战略调整。2015年 USGS 优先项目预算提案中增资内容主要包括生态环境修复、水资源管理、与非常规天然气开发相关的水力压裂影响研究、数据更新与制图、可持续能源开发等几个方面。在分析近20年来美国地质调查局重点工作变化的基础上,提出了中国地质调查工作应紧密围绕我国经济新常态形势下的国家需求,以生态文明建设为核心,加强对清洁能源、矿产和地下水资源的调查力度,为保障经济社会发展需求服务。     

Germanium Contents of USGS Standard Rocks by Flameless Atomic Absorption

Germanium in 13 USGS standard silicate rooks was determined by flameless atomic absoprtion using a procedure which permits the determination of 0.2 ppm of germanium in as little as 50 mg of sample. The mean germanium content found is (in ppm Ge) for the new USGS standards: BHVO-1, 1.60; SDC, 1. 51; STM-1, 1. 32; QLO-1, 1. 28; RGM-1, 1. 24; and for- the older USGS standards: W-l, 1.S3; BCR-1, 1.39; G-l, 1.19; GSP-1, 1.16; AGV-1, 1.06; G-2, 0.96; PCC-1, 0.80; DTS-1, 0.72.     

1988 Compilation of Elemental Concentration Data for USGS Basalt BCR-1

Concentration data on up to 82 individual constituents in USGS Basalt BCR-1 have been collected from 1395 journal articles and technical reports. These data are summarized in consensus (mean) values with uncertainties expressed as ± one standard deviation. Mean values are also calculated as a function of analytical procedure and all raw data are given in the tables. Recommended values are proposed based upon data criteria used by NIST (National Institute of Standards and Technology, formerly the National Bureau of Standards or NBS).     

USGS Reference Samples Attapulgite ATT-1 and Bentonite CSB-1

The U.S. Geological Survey has prepared an attapulgite and a bentonite as reference samples because of their economic importance. The attapulgite (ATT-1) is from the Meigs-Attapulgite-Quincy fuller's earth district of Georgia and Florida, and the bentonite (CSB-1) is from the Northern Black Hills bentonite district of Wyoming, Montana, and South Dakota. The chemical and mineralogical properties of these two samples are quite different. Provisional values calculated from the few analytical data and the X-ray diffraction mineralogy are presented for those who wish to use the clays as reference samples.     

Determination of Fluorine, Chlorine and Water in Eight USGS Reference Samples

Eight reference samples from the U.S. Geological Survey have been analysed for their contents of F, Cl and water. After pyrolysis F was determined with an ion-selective electrode, Cl by colorimetry and water by Karl-Fischer titration.     

Determination of Niobium in 15 USGS Standard Rocks by NEutron Activation Analysis

The niobium concentrations in 15 U.S.G.S. standard rocks were measured by neutron activation analysis. The niobium was separated from the rock matrix (in the presence of ⁹⁵Nb tracer, which was used to measure the fraction recovered) before irradiation to improve the sensitivity. Results of this work are compared with those obtained by other techniques. Some results obtained by multielement X-ray fluorescence procedures agree well with the present data, but a systematic disagreement exists between these and the spectrophotometric data.     

Compilation of Boron Concentration Data for NBS, USGS and CCRMP Reference Materials

Boron concentration data on 69 different biological, coal and geological reference materials issued by NBS, USGS and CCRMP have been collected from 1951-1986. Data from 135 journal articles and technical reports are included. These data are summarized in consensus (mean) values with uncertainties expressed as pm one standard deviation. Mean values are also calculated as a function of analytical procedure and all raw data are given in the tables.     

Instrumental Neutron Activation Determination of 23 Elements in 8 New USGS Standard Rocks

The trace elements Ce, Co, Cr, Cs, Dy, Eu, Gd, Hf, La, Nd, Ni, Rb, Sb, Sc, Sm, Ta, Tb, Th, Tm, U, V, Yb and Zr have been determined by instrumental neutron activation analysis and U by delayed neutron counting in the USGS standard rock samples STM-1, RGM-1, QLO-1, SDC-1, BHVO-1, SCo-1, SGR-1 and MAG-1. The results are compared with those found in the literature.     

Determination of Fluorine and Chlorine in Eight USGS Reference Samples Using Automated Photometric Analysis

Eight USGS reference samples have been analysed for F and Cl by automated photometric analysis following alkali fusion. The results obtained are, generally, in fairly good agreement with those quoted in the literature.     

中国石油资源安全评价

通过分析石油安全的影响因素, 分短期和长期分别建立了石油安全评价指标体系。运用层次分析法评估了中国不同阶段的石油安全, 其结果表明: 石油市场(短期)安全随着价格变化而不断波动; 石油战略(长期)安全随着我国石油消费量的不断上升, 石油安全状况呈现下降趋势。     

Determination of Platinum in USGS Manganese Nodule Reference Samples by a Fire Assay-Spectrographic Method

Data on platinum in manganese nodules by a combined fire assay-spectrographic procedure agree reasonably well with data obtained by a fire-assay flameless atomic-absorption spectroscopic method. A plea is made for the contribution of much more data on Pt in these samples for arriving at valid conclusions and for showing their geochemical and economical interest.     

Atomic Absorption Analysis of USGS Reference Sample Marine Mud MAG-1 for Selected Trace Elements

USCS reference sample marine mud MAG-1 has been analyzed for 12 trace elements by flame atomic absorption spectrophotometry (11 elements) and graphite furnace (Cd). Individual and mean values are given and compared to published data. Precision as % coefficient of variation is given and the relative accuracy of the method assessed in relation to established rock standards.