Dating Unit P at Kromdraai

The purpose of this study is to perform a U-Pb dating on the samples. The ultimate goal is dating the Kromdraai sedimentary unit where the samples come from. Sampling is done by pulverizing the samples in a mortar. Samples are leached, for cleaning, with cold 0.1 mol/L acetic acid. Saples are dissolved in 4.5 mol/L HNO3. One aliquot is taken from each sample and used for measuring REE abundance and the 238U/206Pb ratio on a quadrupole ICP-MS, with In as an internal standard. Another aliquot is taken and used to extract U on anion exchange resin. Matrix is eluted with 9 mol/L HCl, U is eluted with 0.1 mol/L HCl. This aliquot is then used to measure the 234U/238U ratio on a multi-collector ICP-MS, with standard (NIST) bracketing to correct instrumental drift. The rest of each sample is used to extract Pb on anion exchange resin. Matrix is eluted with 1 mol/L HBr, Pb is eluted with 6 mol/L HCl. This fraction is then used to measure Pb isotope composition on a multi-collector ICP-MS, with Tl doping to correct mass-dependent instrumental isotope fractionation and standard (NIST) bracketing to correct instrumental drift.