Drivers for late Paleozoic to early Mesozoic orogenesis in South China: Constraints from the sedimentary record

摘要

Unconformity bound Permo-Triassic successions in the Qinfang Basin, South China Craton, reflect tectonic processes associated with tectonothermal activity along the margins of the craton. The provenance record of these successions, based on modal analysis, geochemical composition, detrital zircon U–Pb ages, and paleocurrent data indicate derivation from the adjoining Precambrian Yunkai massif and surrounding Paleozoic sedimentary units. The quartz dominated nature of the siliciclastic units, along with their high Th/Sc and Zr/Sc ratios indicate a recycled orogen source. Detrital zircons fromLate Permian to Early Triassic samples displaymajor age groups at 1100–800 Ma, 650–500 Ma, 480–420 Ma, with subordinate age groups at 2800–2400 Ma, 1900–1600 Ma and 1400–1200 Ma. Late Triassic sandstones show a similar detrital zircon age pattern as well as a 300–250 Ma age group. Integration of this provenance data with regional geological information suggests that the unconformity at the base of the Permian succession is related to subduction of the Paleo-Tethys ocean to the south of the craton, whereas the major driver for Triassic tectonic activity corresponds with terrane accretion and the termination of Paleo-Tethys Ocean subduction along the southwest margin of the craton.