STUDY ON THE TECTONIC EVENTS IN THE SYSTEM OF THE LONGMEN MOUNTAIN-WEST SICHUAN FORELAND BASIN, CHINA

There are seven tectonic events in the system of the Longmen Mountain West Sichuan Foreland Basin, depending on the Ar Ar dating, zircon and apatite fission track analyses and dating, ESR dating and computer modeling. The first tectonic event (D 1) took place at the end of the Carnian stage, formed S 1 cleavage and F 1 fold, and resulted in the regional low temperature dynamical metamorphism. The second tectonic event (D 2) at the end of Norian stage resulted in the formation of conglomerate of the Fourth Member of Upper Triassic Xujiahe Formation, the unconformity between the Fourth Member of Upper Triassic Xujiahe Formation and its underlying rocks, and strong magmatism. The third event (D 3) happened at 120~130 Ma and made strong magmatism and metamorphism. The other four tectonic events (D 4, D 5, D 6, D 7) took place at 60 Ma, 30~40 Ma, 20~25 Ma, and 10 Ma, respectively and made the system of the Longmen Mountain West Sichuan Foreland Basin thrusting and uplifting.