The timing of the initial collision between the South and North China blocks constraining from the sediments in the eastern Sichuan Basin.

ABSTRACT

In this study, detrital zircon U-Pb geochronology, trace element and Hf isotopic compositional data from the Early-Middle Triassic clastic rocks in the eastern Sichuan Basin were obtained to distinguish the sediment provenance and constrain the timing of the initial collision between the South China and North China blocks. Detrital zircons from the Early Triassic Feixianguan Formation clastic rocks yield one major age peak at 2476 Ma and three minor age peaks at 1886, 802 and 304 Ma. These detrital zircons may be derived from the South China Block. Detrital zircons from the Early Triassic Jialingjiang Formation clastic rocks yield multiple age peaks at 979, 856, 392 and 269 Ma, indicating a mixed sediment provenance from the South China Block and Qinling Orogenic Belt. This is the first appearance of the detritus with the Qinling Orogenic Belt affinity in the eastern Sichuan Basin. Detrital zircons from the Middle Triassic Leikoupo Formation clastic rocks yield two centralized age peaks at 447 and ca. 245 Ma. These zircons may mainly be derived from the Qinling Orogenic Belt. The results indicate an abrupt change in the detrital zircon U-Pb provenance from the South China Block to the Qinling Orogenic Belt during the Early-Middle Triassic. Integrating the provenance change and other geological characteristics, we suggest that the initial collision in the eastern Qinling Orogenic Belt occurred in the Early Triassic.