Despite the significant improvement on spatial resolution, NanoSIMS still preserves relatively high mass resolution, sensitivity, and analytical precision. It has become an important analytical platform to determine c...Despite the significant improvement on spatial resolution, NanoSIMS still preserves relatively high mass resolution, sensitivity, and analytical precision. It has become an important analytical platform to determine chemical compositions of solid materials, and has been widely used in space, earth, life, and materials sciences, etc. By using a Cs＋ ion beam with a size as small as 50 nm scanning over sample surfaces, we are able to obtain high spatial resolution images of up to 7 species simultaneously. When utilizing Faraday cup, high analytical precision of 0.3‰-0.5‰ （1SD） for C, O and S isotopic analysis can be achieved. Although this precision level is still lower than that of conventional SIMS, it already meets the major requirements of Earth Sciences. In 2011, the first NanoSIMS of China （Cameca NanoSIMS 50L） was installed at Institute of Geology and Geophysics, Chinese Academy of Sciences. Based on the working mechanism and analytical modes of the instrument, this paper will systematically introduce the analytical methods established with the NanoSIMS and their potential applications in earth sciences. These methods include trace element distribution images in mineral zoning, high spatial resolution （2-5/am） Pb-Pb and U-Pb dating, water content and H isotopic analysis for silicate glass and apatite, C isotopic analysis for diamond and graphite, O isotopic analysis for carbonate, S isotopic analysis for sulfides. In addition, the specific requirements for sample preparation will also be introduced in order to facilitate domestic earth scientists＇ use.展开更多
We report an imaging method of zircon U-Pb dating with NanoSIMS 50 L, which overcomes the significant U-Pb fractionation as the pit was sputtered deeper during conventional spot mode analysis and can be applied to irr...We report an imaging method of zircon U-Pb dating with NanoSIMS 50 L, which overcomes the significant U-Pb fractionation as the pit was sputtered deeper during conventional spot mode analysis and can be applied to irregular small grains or heterogeneous areas of zircon. The U-Pb and Pb-Pb ages can be acquired simultaneously for 2 μm×2 μm(for small grains) or 1 μm×9 μm(for zoned grains), together with Zr, Y and other trace elements distributions. Using zircon M257 as standard, the U-Pb ages of other zircon standards, including Qinghu, Plesovice, Temora and 91500, were measured to(2σ) as158.8±0.8, 335.9±3.4, 412.0±12 and 1067±12 Ma, respectively, consistent with the recommended values within the analytical uncertainties. Tiny zircon grains in the impact melt breccia of the lunar meteorite SaU 169 were also measured in this study,with a Pb-Pb age of 3912±14 Ma and a U-Pb age of 3917±17 Ma, similar to previous results reported for the same meteorite.The imaging method was also applied to determine U-Pb age of the thin overgrowth rims of Longtan metamorphic zircon, with a Pb-Pb age of 1933±27 Ma and a U-Pb age of 1935±25 Ma, clearly distinct from the Pb-Pb age of 2098±61 Ma and the U-Pb age of 2054±40 Ma for detrital cores.展开更多
基金supported by the National Natural Science Foundation of China(Grants Nos.41173012,41103031,41230209,41322022,41221002)
文摘Despite the significant improvement on spatial resolution, NanoSIMS still preserves relatively high mass resolution, sensitivity, and analytical precision. It has become an important analytical platform to determine chemical compositions of solid materials, and has been widely used in space, earth, life, and materials sciences, etc. By using a Cs＋ ion beam with a size as small as 50 nm scanning over sample surfaces, we are able to obtain high spatial resolution images of up to 7 species simultaneously. When utilizing Faraday cup, high analytical precision of 0.3‰-0.5‰ （1SD） for C, O and S isotopic analysis can be achieved. Although this precision level is still lower than that of conventional SIMS, it already meets the major requirements of Earth Sciences. In 2011, the first NanoSIMS of China （Cameca NanoSIMS 50L） was installed at Institute of Geology and Geophysics, Chinese Academy of Sciences. Based on the working mechanism and analytical modes of the instrument, this paper will systematically introduce the analytical methods established with the NanoSIMS and their potential applications in earth sciences. These methods include trace element distribution images in mineral zoning, high spatial resolution （2-5/am） Pb-Pb and U-Pb dating, water content and H isotopic analysis for silicate glass and apatite, C isotopic analysis for diamond and graphite, O isotopic analysis for carbonate, S isotopic analysis for sulfides. In addition, the specific requirements for sample preparation will also be introduced in order to facilitate domestic earth scientists＇ use.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 41430105, 41490631, 41573057 & 41521062)
文摘We report an imaging method of zircon U-Pb dating with NanoSIMS 50 L, which overcomes the significant U-Pb fractionation as the pit was sputtered deeper during conventional spot mode analysis and can be applied to irregular small grains or heterogeneous areas of zircon. The U-Pb and Pb-Pb ages can be acquired simultaneously for 2 μm×2 μm(for small grains) or 1 μm×9 μm(for zoned grains), together with Zr, Y and other trace elements distributions. Using zircon M257 as standard, the U-Pb ages of other zircon standards, including Qinghu, Plesovice, Temora and 91500, were measured to(2σ) as158.8±0.8, 335.9±3.4, 412.0±12 and 1067±12 Ma, respectively, consistent with the recommended values within the analytical uncertainties. Tiny zircon grains in the impact melt breccia of the lunar meteorite SaU 169 were also measured in this study,with a Pb-Pb age of 3912±14 Ma and a U-Pb age of 3917±17 Ma, similar to previous results reported for the same meteorite.The imaging method was also applied to determine U-Pb age of the thin overgrowth rims of Longtan metamorphic zircon, with a Pb-Pb age of 1933±27 Ma and a U-Pb age of 1935±25 Ma, clearly distinct from the Pb-Pb age of 2098±61 Ma and the U-Pb age of 2054±40 Ma for detrital cores.
