RMJG Rutile: A New Natural Reference Material for Microbeam U-Pb Dating and Hf Isotopic Analysis

Matrix-matched reference materials are necessary for accurate microbeam U-Pb dating and Hf isotopic determination. This study introduces the RMJG rutile as a new potential reference material, which was separated from Palaeoproterozoic pelitic granulites collected in Hebei Province, China. LA-ICP-MS measurements indicate the RMJG rutile has extremely low Th (< 0.003 +/- 0.01 mu g g(-1)) and common Pb contents, but high Hf (102 +/- 34 mu g g(-1)), U (61 +/- 11 mu g g(-1)), and radiogenic Pb ( 20 mu g g(-1)) contents. Moreover, the rutile yields relatively constant U-Pb ages and Hf isotopic data. The LA-ICP-MS analyses suggest that this rutile has a concordant U-Pb age with a statistical mean Pb-206/U-238 and Pb-207/U-235 ages of 1749.9 +/- 32.1 Ma and 1750.0 +/- 26.4 Ma, respectively (2s), which are statistically indistinguishable from its ID-TIMS ages (1750.6 +/- 8.4 and 1750.1 +/- 4.7 Ma). Precise determination of the Hf-176/Hf-177 ratio by MC-ICP-MS in solution mode (0.281652 +/- 0.000006) is in good agreement with the statistical mean of the LA-MC-ICP-MS measurements (0.28166 +/- 0.00018). Therefore, the limited variations of RMJG U-Pb age and Hf isotopic composition together with its extremely low common Pb and high Hf, U and Pb contents make it an ideal calibration and monitor reference material for LA-ICP-MS measurements.