Abstract

GONZALEZ-GUZMAN, Reneé; WEBER, Bodo; TAZZO-RANGEL, María D.  and  SOLARI, Luigi. Validation of digestion and element separation methods and a new data reduction program (IsotopeHf^®) for Lu-Hf isotope dilution analysis by MC-ICP-MS. Rev. mex. cienc. geol [online]. 2016, vol.33, n.2, pp.254-269. ISSN 2007-2902.

The Lu-Hf isotope system is not only an important geo chronometer but also a powerful tool for petrogenetic studies. To determine reliable analytical results of this system from rock and mineral samples, a protocol is established that includes appropriate sample digestion, a three-stage HREE-Hf ion-exchange separation procedure, a data acquisition protocol by MC-ICP-MS, and an R-based data reduction software package (IsotopeHf®) that transforms raw mass spectrome-try data into meaningful isotopie ratios, including all the necessary corrections for spiked samples. Our 176Hf/177Hf results of both mafic and felsic geochemical reference standards agree with those reported by other authors. However, results obtained using PicoTrace® pressure digestion system (DAS®) yield significantly higher 176Lu/177Hf for felsic rocks with high Hf content (> 15 ppm) compared to data obtained by Parr® bomb dissolution, indicating incomplete digestion of HFSE-rich phases like zircon under specific conditions of DAS® digestion. The high degree of Hf purity attained using our chemical procedure, MCI CP-MS measurement protocol, and the IsotopeHf® program yielded accurate data with reliable and reproducible Lu-Hf isotope ratios within typical analytical uncertainties.

Keywords : Lu-Hf; MC-ICP-MS analysis; digestion methods; data reduction software; geochemical reference standards.

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