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 Lu-176/Hf-177=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 Munster) yield an average present day Hf-176/Hf-177 of 0.282000 +/- 0.000005 (2 sigma 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 Hf-176/Hf-177 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 Hf-176/Hf-177, pointing to possible small scale inhomogeneity with elevated HREE contents. (C) 2008 Elsevier B.V. All rights reserved.