DQPB: software for calculating disequilibrium U–Pb ages

Abstract

Abstract. Initial radioactive disequilibrium amongst intermediate nuclides of the U decay chains can have a significant impact on the accuracy of U–Pb ages, especially in young samples. For samples that can reasonably be assumed to have attained radioactive equilibrium at the time of analysis, a relatively straightforward correction may be applied. However, in younger materials where this assumption is unreasonable, it is necessary to replace the familiar U–Pb age equations with more complete expressions that account for growth and decay of intermediate nuclides through time. DQPB is software for calculating U–Pb ages while accounting for the effects of radioactive disequilibrium among intermediate nuclides of the U decay chains. The software is written in Python and distributed as both a pure Python package and a stand-alone graphical user interface (GUI) application that integrates with standard Microsoft Excel spreadsheets. The software implements disequilibrium U–Pb equations to compute ages using various approaches, including concordia intercept ages on a Tera–Wasserburg diagram, U–Pb isochron ages, Pb*/U ages based on single aliquots, and 207Pb-corrected ages. While these age-calculation approaches are tailored toward young samples that cannot reasonably be assumed to have attained radioactive equilibrium at the time of analysis, they may also be applied to older materials where disequilibrium is no longer analytically resolvable. The software allows users to implement a variety of regression algorithms based on both classical and robust statistical approaches, compute weighted average ages and construct customisable, publication-ready plots of U–Pb age data. The regression and weighted average algorithms implemented in DQPB may also be applicable to other (i.e. non-U–Pb) geochronological datasets.