Vice Professor YANG Wei and his team report a new method of Pb-Pb dating for zircon and baddeleyite with a lateral resolution of <2μm and U-Pb dating for zircon with a lateral resolution of <5μm using CAMECA NanoSIMS 50L. The O-primary beam was optimized to a current of ~500 pA with a diameter of 1.7μm. The zircon standard M257 and baddeleyite standard Phalaborwa were dated by the Pb-Pb method, yielding 207Pb/206Pb ages of 563±14 Ma and 2058 ±6 Ma, respectively. These results agree well with the recommended ages within analytical uncertainties. Four zircon standards, including Qinghu, Plesovice, Temora, and 91500 were dated by the U-Pb method.

Their study demonstrates that Pb-Pb ages of zircon and baddeleyite can be determined with a lateral resolution of <2μm, and U-Pb ages of zircon can be measured with a lateral resolution of <5μm by CAMECA NanoSIMS. This technique will have important applications to high lateral resolution dating, such as thin layers of zoned zircons, small grains of lunar zircon, and micron-sized baddeleyites in Martian meteorites and in various achondrites from differentiated asteroids.

Fig. Pb-Pb dating results of standard zircons M257 and U-Pb dating results of standard zircons Qinghu. (Image by YANG)

Yang et al. Precise micrometre-sized Pb-Pb and U-Pb dating with NanoSIMS. Journal of Analytical Atomic Spectrometry. 2012, 27(3): 479-487(Download Here)