Community Derived Standards for LA ICP MS U (Th )Pb Geochronology Uncertainty Propagation, Age Interpretation and Data Reporting
The LA ICP MS U (Th )Pb geochronology international community has defined new standards for the determination of U (Th )Pb ages. A new workflow defines the appropriate propagation of uncertainties for these data, identifying random and systematic components. Only data with uncertainties relating to random error should be used in weighted mean calculations of population ages; uncertainty components for systematic errors are propagated after this stage, preventing their erroneous reduction. Following this improved uncertainty propagation protocol, data can be compared at different uncertainty levels to better resolve age differences. New reference values for commonly used zircon, monazite and titanite reference materials are defined (based on ID TIMS) after removing corrections for common lead and the effects of excess 230Th. These values more accurately reflect the material sampled during the determination of calibration factors by LA ICP MS analysis. Recommendations are made to graphically represent data only with uncertainty ellipses at 2s and to submit or cite validation data with sample data when submitting data for publication. New data reporting standards are defined to help improve the peer review process. With these improvements, LA ICP MS U (Th )Pb data can be considered more robust, accurate, better documented and quantified, directly contributing to their improved scientific interpretation.