Late Paleozoic-Mesozoic Basin Evolution In The Longmenshan-Dabashan Region And Its Tectonic Implications

The Late Paleozoic-Mesozoic strata of the Logmenshan-Dabashan area, northwestern Sichuan Province, are selected for the basin evolution study. We adopted the detrital zircon U-Pb geochronology and sandstone petrography to decipher the provenance of Late Paleozoic-Mesozic strata. Our results in combination with the previous researches indicate that the major provenance of the Northwest Sichuan basin during Permian is the Yangtz Block. While during middle Triassic period sediments were contributed by Qinling orogen and North China block in addition to Yangtz block. The sediment provenance for northwest Sichuan basin and Songpan-Ganzi basin is same until Jurassic. It indicates that the western part of South and North China blocks collided before Anisian(226-245Ma). Moreover, Based on the zircon age data from Triassic and Jurassic strata in Songpan-Ganzi and our research area, we concluded that the exhumation of the Longmenshan mountain was limited until late Triassic and significant uplift occurred in Jurassic.