Determination of Mercury in One Hundred and Sixteen Geological and Environmental Reference Materials Using a Direct Mercury Analyser

The mercury content of 116 reference materials (RMs) from ten international organisations was determined in this study, which focused on variability within and between batches of RMs. Direct mercury analysis (DMA) was applied to RMs having Hg contents between 1 and 6300 ng g^?1 and provided good precision and accuracy. Accuracy was demonstrated by the agreement of our results with certified values, while replicates were made to establish the precision. Low within‐batch variability was noted, with precision from 0.1 to 23% (n = 3–5) apparently depending on Hg content and homogeneity, whereas systematic offsets were detected among several batches. Thanks to the analysis of different batches; the homogeneity or heterogeneity of several RMs was shown, and thus, suitable RMs for quality control for Hg determinations could be recommended.     

The Preparation of Marine Geological Certified Reference Materials - Polymetallic Nodule GSPN-1 and Marine Sediment GSMS-1 from the Central Pacific Ocean*

This report describes the location, collection, preparation, homogeneity testing, analysis, data-processing and assignment of certified values of a polymetallic nodule (GSPN-1) and marine sediment (GSMS-1). Materials used in the preparation of these reference materials were collected in 1986 and 1987 from the central Pacific Ocean, by the Chinese Ministry of Geology and Mineral Resources (MGMR). A total of fifty one recommended element concentrations and five proposed concentrations are reported for GSPN-1. For GSMS-1, a total of fifty recommended and seven proposed values are presented.     

Caractérisation des ignimbrites néogènes du bassin d'Arequipa,Pérou

Four ignimbritic units have filled the Arequipa Basin and outcrop around the Chachani Volcano. (1) The oldest Río Chili ignimbrite is 13.33 Ma old; (2) the most widespread La Joya ignimbrite is 4.9 Ma old; (3) the Arequipa Airport ignimbrite (1.65 Ma) flowed from an area buried beneath Chachani; (4) the Yura Tuffs, 1.02 Ma old, are restricted to the west of Chachani. All are calc-alkaline rhyolites with plagioclase, biotite, quartz, sanidine, and opaques, but the Río Chili and La Joya ignimbrites also contain amphibole. Trace elements of the older ignimbrites reflect stronger crustal influence. To cite this article: P. Paquereau et al., C. R. Geoscience 337 (2005).     

Modélisation du festonnage des barres sableuses d'avant-côte : application à la côte aquitaine,France

Nearshore crescentic bars play a key role in nearshore morphodynamics. These bars are observed all along the Aquitanian Coast, with a mean wavelength of about 700 m. A non-linear stability analysis is undertaken to simulate the development of crescentic patterns. Results show that self-organization mechanism can lead alone to the development of these alongshore rhythmic features. Simulated wavelengths are in agreement with observations on the Aquitanian Coast. To cite this article: B. Castelle et al., C. R. Geoscience 338 (2006).     

Estimates of present-day erosion based on sediment transport in rivers: a case study in Taiwan

We discuss the present-day sediment transport by rivers, and hence the erosion rate in upstream basins, based on the example of Taiwan Rivers where large datasets are available. After data correction, the values of the suspended sediment load in the lower Kaoping River are nearly three times smaller than those from the literature. On the other hand, we add the bed load evaluated from numerical modelling, despite limitations from data and models. Whereas the contribution of the chemical denudation rate in Taiwan is minor, the bed load is significant and must be evaluated. We point out that biases in data collection may favour high values of suspended load data, and that large series of datasets are needed to reduce uncertainties and smooth the time variability effect. To cite this article: F.-C. Li et al., C. R. Geoscience 337 (2005).     

Determination of Cr,Cu, Ni,Sn, Sr and Zn Mass Fractions in Geochemical Reference Materials by Isotope Dilution ICP‐MS

Isotope dilution (ID) mass spectrometry is a primary method of analysis suited for the accurate and precise measurement of several trace elements in geological matrices. Here we present mass fractions and respective uncertainties for Cr, Cu, Ni, Sn, Sr and Zn in 10 silicate rock reference materials (BCR‐2, BRP‐1, BIR‐1, OU‐6, GSP‐2, GSR‐1, AGV‐1, RGM‐1, RGM‐2 and G‐3) obtained by the double ID technique and measuring the isotope ratios with an inductively coupled plasma‐mass spectrometer equipped with collision cell. Test portions of the samples were dissolved by validated procedures, and no further matrix separation was applied. Addition of spikes was designed to achieve isotope ratios close to unity to minimise error magnification factors, according to the ID theory. Radiogenic ingrowth of ⁸⁷Sr from the decay of ⁸⁷Rb was considered in the calculation of Sr mass fractions. The mean values of our results mostly agree with reference values, considering both uncertainties at the 95% confidence level, and also with ID data published for AGV‐1. Considering all results, the means of the combined uncertainties were < 1% for Sr, approximately 2% for Sn and Cu, 4% for Cr and Ni and almost 6% for Zn.     

New UPb zircon ages from Tonga (Cameroon): coexisting Eburnean–Transamazonian (2.1 Ga) and Pan-African (0.6 Ga) imprints

The central domain of the Pan-African Belt in Cameroon is characterized by abundant porphyritic granitoids, which were emplaced synkinematically and variably orthogneissified in relation with ENE-striking steeply dipping transcurrent shear zones. These plutonic rocks have intermediate to felsic compositions and constitute a high-K calk-alkaline series. Conventional UPb zircon dating yields an age of 618 Ma for this syntectonic Pan-African magmatism in the Tonga area. The country rocks are made of metabasites (garnet amphibolites) and tonalitic to trondhjemitic gneisses, which suffered two distinct orogenic cycles: the first one is the Palaeoproterozoic Eburnean–Transamazonian cycle at 2.1 Ga and the second one is the Pan-African orogenesis. These new ages confirm the existence of an extensive Palaeoproterozoic crust in Cameroon and question the areal extent of the Congo–São Francisco craton towards the north. To cite this article: E.L. Tanko Njiosseu et al., C. R. Geoscience 337 (2005).     

Proposal for an International Molybdenum Isotope Measurement Standard and Data Representation

Molybdenum isotopes are increasingly widely applied in Earth Sciences. They are primarily used to investigate the oxygenation of Earth's ocean and atmosphere. However, more and more fields of application are being developed, such as magmatic and hydrothermal processes, planetary sciences or the tracking of environmental pollution. Here, we present a proposal for a unifying presentation of Mo isotope ratios in the studies of mass‐dependent isotope fractionation. We suggest that the δ^98/95Mo of the NIST SRM 3134 be defined as +0.25‰. The rationale is that the vast majority of published data are presented relative to reference materials that are similar, but not identical, and that are all slightly lighter than NIST SRM 3134. Our proposed data presentation allows a direct first‐order comparison of almost all old data with future work while referring to an international measurement standard. In particular, canonical δ^98/95Mo values such as +2.3‰ for seawater and ?0.7‰ for marine Fe–Mn precipitates can be kept for discussion. As recent publications show that the ocean molybdenum isotope signature is homogeneous, the IAPSO ocean water standard or any other open ocean water sample is suggested as a secondary measurement standard, with a defined δ^98/95Mo value of +2.34 ± 0.10‰ (2s).     

δ98/95Mo values and Molybdenum Concentration Data for NIST SRM 610, 612 and 3134: Towards a Common Protocol for Reporting Mo Data

Molybdenum concentration and δ^98/95Mo values for NIST SRM 610 and 612 (solid glass), NIST SRM 3134 (lot 891307; liquid) and IAPSO seawater reference material are presented based on comparative measurements by MC‐ICP‐MS performed in laboratories at the Universities of Bern and Oxford. NIST SRM 3134 and NIST SRM 610 and 612 were found to have identical and homogeneous ⁹⁸Mo/⁹⁵Mo ratios at a test portion mass of 0.02 g. We suggest, therefore, that NIST SRM 3134 should be used as reference for the δ–Mo notation and to employ NIST SRM 610 or 612 as solid silicate secondary measurement standards, in the absence of an isotopically homogeneous solid geological reference material for Mo. The δ^98/95Mo_{JMC Bern} composition (Johnson Matthey ICP standard solution, lot 602332B as reference) of NIST SRM 3134 was 0.25 ± 0.09‰ (2s). Based on five new values, we determined more precisely the mean open ocean δ^98/95Mo_{SRM 3134} value of 2.09 ± 0.07‰, which equals the value of δ^98/95Mo_{JMC Bern} of 2.34 ± 0.07‰. We also refined the Mo concentration data for NIST SRM 610 to 412 ± 9 μg g^?1 (2s) and NIST SRM 612 to 6.4 ± 0.7 μg g^?1 by isotope dilution. We propose these concentration data as new working values, which allow for more accurate in situ Mo determination using laser ablation ICP‐MS or SIMS.     

Determination of Incompatible Trace Elements in Mantle Clinopyroxenes by LA-ICP-MS: A Comparison of Analytical Performance with Established Techniques

Incompatible trace element abundances have been determined in mantle-derived clinopyroxenes by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in a comparative study with established microanalytical and bulk techniques. Individual clinopyroxene grains were sampled for the laser ablation study from sieved mineral separate fractions, from which similar mineral grains had been previously extracted for microprobe (SIMS) and bulk (INAA and ID-TIMS) analysis. Mineral grains were ablated with variable degrees of surface spatial resolution (50-200 μm) in order to maximise ICP-MS analyte count rates and to improve detection limits. A comparison of results from the different techniques reveals that for the most homogeneous samples LA-ICP-MS can achieve excellent levels of agreement with other techniques (10%) and good precision for most of the studied elements (1-5% RSD). Variations in calculated concentrations by LA-ICP-MS confirm inter- and intra-mineral heterogeneity determined by SIMS, reflecting changes in sample composition and texture. The long-term reproducibility of the technique is shown by the consistency of results for one sample analysed on thirteen occasions over a period of nine months.