Zircon fission-track and U-Pb double dating using femtosecond laser ablation-inductively coupled plasma-mass spectrometry: A technical note

We present a new LA-ICP-MS system for zircon fission-track (FT) and U-Pb double dating, whereby a femtosecond laser combined with galvanometric optics simultaneously ablates multiple spots to measure average surface U contents. The U contents of zircon measured by LA-ICP-MS and standardized with the NIST SRM610 glass are comparable to those measured by the induced FT method, and have smaller analytical errors. LA-ICP-MS FT dating of seven zircon samples including three IUGS age standards is as accurate as the external detector method, but can give a higher-precision age depending on the counting statistics of the U content measurement. Double dating of the IUGS age standards gives FT and U-Pb ages that are in agreement. A chip of the Nancy 91500 zircon has a homogeneous U content of 84 ppm, suggesting the possibility of using this zircon as a matrix-matched U-standard for FT dating. When using the Nancy 91500 zircon as a U-standard, a zeta calibration value of 42-43 year cm(2) for LA-ICP-MS FT dating is obtained. While this value is strictly valid only for the particular session, it can serve as a reference for other studies.