Distribution of U and Th in apatites: implications for U-Th/He thermochronology

The U-Th/He thermochronology technique assumes a homogeneous distribution of U and Th within the analysed crystals. Cathodoluminescence imaging reveals a strong chemical heterogeneity within apatite a mineral widely used for U-Th/He dating. This heterogeneity is then susceptible to induce large errors when calculating the U-Th/He age. Chemical analysis using laser ablation ICP-MS of the various zones shown by cathodoluminescence display a link between the Ce, U and Th concentration and the luminescence intensity allowing the U-Th/He age to be corrected for zonation. (C) 2003 Academie des sciences. Publie par Editions scientifiques et medicales Elsevier SAS. Tons droits reserves.