Calibration method for ¹⁹⁰Os spike content based on recommended age of standard reference materials

The Rhenium-Osmium (Re-Os) isotope system is a key technique for the direct dating and genetic tracing of metallic ore deposits, sedimentary strata, and other geological materials, while Isotope Dilution-Negative-Thermal Ionization Mass Spectrometry (ID-N-TIMS) is currently the most widely used analytical method. Herein, the compositional accuracy of the 190Os spike is critical for maintain the reliability of dating results; however, the content of the laboratory calibrated 190Os spike tends to drift due to external physical factors such as temperature fluctuations and solvent evaporation. Therefore, this study established a rapid and efficient spike content correction method, a traceability correction method centered on the recommended age of the Huanglongpu molybdenite reference material (GBW04435; HLP), which was reverse verified using the reverse dilution method with Os standard solution. The experimental results show that when correcting the 190Os spike content based on the recommended age and original model age, the weighted average correction factors are 1.057±0.010 (95% confidence level) and 1.054±0.012 (95% confidence level), respectively. Correspondingly, the weighted average 190Os spike contents are (112.46±1.06)×10-9 and (112.14±1.28)×10-9, respectively. The reverse dilution correction results of the Os standard solution indicate that the 190Os spike content is (111.28±1.28)×10-9, which is essentially consistent with the recommended age correction results within the 2σ error range. This combined main-auxiliary correction method not only provides a simple and efficient solution for verifying spike composition but also significantly reduces random errors via the auxiliary calibration mechanism. Compared with traditional methods, it greatly shortens the time and cost of secondary calibration of the 190Os spike and significantly improves the accuracy and reproducibility of Re-Os isotope dating of molybdenite. It is important to note that this method is premised on the traditional calibration of the spike. Currently, it is primarily employed for the systematic, simplified correction of post-calibration 190Os spike content. However, to achieve higher dating precision and accuracy, integration with the traditional precise calibration protocol for the 190Os spike remains necessary.