Hafnium isotope characterization of the GJ-1 zircon reference material by solution and laser-ablation MC-ICPMS

Twenty four splits from two different GJ-1 reference material zircon crystals were analyzed for their Lu and Hf concentrations, Lu/Hf and Hf isotopic compositions by solution ID-MC-ICPMS. Lutetium and Hf concentrations are variable between single splits ranging from 9.34 ppm to 14.3 ppm and 4976 ppm to 7719 ppm, respectively, with an average 176Lu/177Hf = 0.00025. Concentrations of both elements show a positive correlation, which argue for in-homogeneity of the zircon with respect to HREE and Hf, and however, do not affect the isotope composition. Solution data from two laboratories (Amsterdam and Münster) yield an average present day 176Hf/177Hf of 0.282000 ± 0.000005 (2σ weighted mean), which we recommend as a reference and nomination value for laser-ablation Hf isotope analyses. Cl imaging shows no visible banding or zonation for CL-active elements. Laser-ablation Hf isotopic analyses yield homogeneous 176Hf/177Hf identical within analytical uncertainties with the value obtained by the solution work, which make these zircons suitable for Hf isotope determinations using LA-MC-ICPMS analyses. Notably, one laser-ablation analysis shows elevated Yb and Lu contents with a significantly lower 176Hf/177Hf, pointing to possible small scale in-homogeneity with elevated HREE contents.