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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.
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 than conventional spot mode analysis and can be applied to irregular small grains or heterogeneous areas of zircon. 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 element distributions. Using zircon M257 as standard, the U-Pb ages of other zircon standards, including Qinghu, Plesovice, Temora and 91500, were measured to (2σ) as 158.8 ± 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. 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.