LAUSR

Abstract U-Pb dating can provide age constraints on carbonate minerals from a wide range of geological settings. A major practical limitation, however, is the need for rapid and efficient extraction of Pb and U from large numbers of typically low-Pb (≤10 ng/g) calcite samples, while maintaining low blanks (∼10 pg Pb) and high Pb-U yields and purity. Here we describe a well-tested ion exchange procedure able to extract Pb and U from large (up to 200 mg) calcite samples using a single pass over a mini-column filled with small (∼0.1 ml) volumes of AG1-X8 anion exchange and Eichrom TRU-resins. This ‘stacked resin’ technique halves the time spent on elemental extractions and provides MC-ICPMS-ready Pb and U fractions in a single day. The method results in considerable savings in laboratory time and allows higher sample throughput, without negative impacts on data quality. It is ideally suited for high-precision U-Pb dating of speleothems where large numbers of samples need to be processed, but it is equally adaptable to calcites from other settings. While not explored as part of this work, the stacked resin technique should also be applicable to other carbonates (dolomite, ankerite, siderite).