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High-precision isotopic characterization of USGS reference materials by TIMS and MC-ICP-MS
Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, 6339 Stores Road, V6T 1Z4 Canada
Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, 6339 Stores Road, V6T 1Z4 Canada
Department of Earth and Environmental Sciences, UniversitéLibre de Bruxelles, CP 160/02, Avenue F.D. Roosevelt, 50, Brussels, B-1050, Belgium
Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, 6339 Stores Road, V6T 1Z4 Canada
Department of Earth and Environmental Sciences, UniversitéLibre de Bruxelles, CP 160/02, Avenue F.D. Roosevelt, 50, Brussels, B-1050, Belgium
Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, 6339 Stores Road, V6T 1Z4 Canada
Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, 6339 Stores Road, V6T 1Z4 Canada
Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, 6339 Stores Road, V6T 1Z4 Canada
Department of Earth and Environmental Sciences, UniversitéLibre de Bruxelles, CP 160/02, Avenue F.D. Roosevelt, 50, Brussels, B-1050, Belgium
Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, 6339 Stores Road, V6T 1Z4 Canada
Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, 6339 Stores Road, V6T 1Z4 Canada
Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, 6339 Stores Road, V6T 1Z4 Canada
Department of Geology, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin, 54702-4004, USA
The Pacific Centre for Isotopic and Geochemical Research (PCIGR) at the University of British Columbia has undertaken a systematic analysis of the isotopic (Sr, Nd, and Pb) compositions and concentrations of a broad compositional range of U.S. Geological Survey (USGS) reference materials, including basalt (BCR-1, 2; BHVO-1, 2), andesite (AGV-1, 2), rhyolite (RGM-1, 2), syenite (STM-1, 2), granodiorite (GSP-2), and granite (G-2, 3). USGS rock reference materials are geochemically well characterized, but there is neither a systematic methodology nor a database for radiogenic isotopic compositions, even for the widely used BCR-1. This investigation represents the first comprehensive, systematic analysis of the isotopic composition and concentration of USGS reference materials and provides an important database for the isotopic community. In addition, the range of equipment at the PCIGR, including a Nu Instruments Plasma MC-ICP-MS, a Thermo Finnigan Triton TIMS, and a Thermo Finnigan Element2 HR-ICP-MS, permits an assessment and comparison of the precision and accuracy of isotopic analyses determined by both the TIMS and MC-ICP-MS methods (e.g., Nd isotopic compositions). For each of the reference materials, 5 to 10 complete replicate analyses provide coherent isotopic results, all with external precision below 30 ppm (2 SD) for Sr and Nd isotopic compositions (27 and 24 ppm for TIMS and MC-ICP-MS, respectively). Our results also show that the first- and second-generation USGS reference materials have homogeneous Sr and Nd isotopic compositions. Nd isotopic compositions by MC-ICP-MS and TIMS agree to within 15 ppm for all reference materials. Interlaboratory MC-ICP-MS comparisons show excellent agreement for Pb isotopic compositions; however, the reproducibility is not as good as for Sr and Nd. A careful, sequential leaching experiment of three first- and second-generation reference materials (BCR, BHVO, AGV) indicates that the heterogeneity in Pb isotopic compositions, and concentrations, could be directly related to contamination by the steel (mortar/pestle) used to process the materials. Contamination also accounts for the high concentrations of certain other trace elements (e.g., Li, Mo, Cd, Sn, Sb, W) in various USGS reference materials.
Received 22 February 2006; accepted 23 May 2006; published 10 August 2006.
Citation: (2006), High-precision isotopic characterization of USGS reference materials by TIMS and MC-ICP-MS, Geochem. Geophys. Geosyst., 7, Q08006, doi:10.1029/2006GC001283.
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