U, Pb and Th atomic environment in synthetic matrix-matched geo-standards

The most recent advances in mineral dating (geo-thermochronology) rely on the analysis of radioactive isotopes in µm3 volumes using Laser-Ablation ICP-MS. However, the efficiency of laser ablation for a given element depends on the minerals host and, matrix-matched standards are thus required. We have developed new protocols to obtain standards of controlled composition (U, Th, Pb) by synthesis routes for magnetite, spinel and calcite. The standards have been successfully tested with LA-ICP-MS and the next step is to characterize the atomic environment of (U, Th, Pb) so that these synthetic standards can be distributed to the geochronology community. XANES on 20BM (ROBL) is the most appropriate technique to achive that goal for the concentrations of interest. Compared with natural standards, a major step forward would be the manufacture of LA-ICP-MS standards with adjustable U, Th and Pb content.