U-Th-Pb chemical dating of monazites using the proton microprobe

Proton Induced X-ray Emission (PIXE) analyses using the proton microprobe h ave been performed to obtain precise concentrations of major and trace elem ents in a range of monazite samples. With the proton microprobe, detection limits for U, Th and Pb are in the ppm range, thus making the instrument vi able for chemical dating, even in young monazite grains with low radiogenic Pb concentrations,The method has been tested successfully on monazites pre viously analysed by the SHRIMP ion microprobe, conventional mass spectromet ry and chemical dating with an electron microprobe. The high sensitivity of the proton microprobe has potential to be used for chemical dating of othe r minerals with U, Th and Pb abundances below the detection limit of the el ectron microprobe (e.g., zircon, sphene, rutile). (C) 1999 Elsevier Science B.V. All rights reserved.