Timing of granite emplacement and cooling in the Songpan-Garze Fold Belt (eastern Tibetan Plateau) with tectonic implications

New U-Pb and Rb-Sr geochronology on syn- and post-orogenic granites provide constraints on the timing of major tectonic events in the Songpan-Garz fold belt, west Sichuan, China. The Ma Nai granite was probably syn-kinematic with the main deformation and yields an age of 197 +/- 6 Ma that is interpreted as an upper age limit of the Indosinian event. Zircons and apatites from the post-kinematic Rilonguan granite also yield Jurassic ages (195 +/- 6 and 181 +/- 4 Ma). The post-orogenic Markam massif gives two ages of 188 +/- 1 and 153 +/- 3 Ma. Both granites are undeformed and cut structures in the Triassic sedimentary rocks. These results demonstrate that the major deformation and decollement tectonics in the Songpan-Garze fold belt occurred prior to the Early Jurassic. The wide range of ages obtained for postkinematic granites (from Early Jurassic to Late Jurassic) suggests that, locally, magmatic activity persisted for a long time (at least 50 Ma) after the Indosinian compressional tectonism. No Tertiary ages have been obtained, suggesting that these granites were not affected strongly by the India-Asia collision. (C) 2003 Elsevier Ltd. All rights reserved.