Electron-microprobe dating of monazite

Abstract. Monazite (LREE, ThO2)PO4 is an accessory mineral in leucogranites and metapelites. It crystallizes with zircon from granitic melts. During metamorphism the formation of monazite is possible at a wide range of conditions. High contents of Th and its decay to Pb during geological time spans provide the prerequisite for a dating method without analysis of isotopic ratios. Monazite Th-U-Pb ages can be calculated from a bulk chemical analysis by electron-microprobe (EMP). This analytical technique is non-destructive and in-situ with a great spatial resolution. Besides the characteristics of monazite and the properties of EMP this paper is focused on the different age calculation methods that have been developed during the last years