Detrital zircon provenance of the lower yangtze foreland basin deposits: Constraints on the evolution of the early palaeozoic wuyi-yunkai orogenic belt in South China

摘要

The Lower Yangtze foreland basin is situated to the northwest of the early Palaeozoic Wuyi-Yunkai orogen in South China. To demonstrate its provenance history and the denudation of the orogen, seven sandstone samples were collected from the upper Ordovician to Silurian strata for U-Pb dating. The zircons show a broad range of ages that can be linked with the ages of specific units in the Wuyi-Yunkai orogen. The zircon spectra in the late Ordovician samples are similar to those in the pre-orogenic strata, suggesting a recycled source. The dominant age population of 880-740 Ma in the early Llandovery samples indicates that the middle Neoproterozoic volcanic rocks were the primary source. A significant age population of 460-425 Ma in the late Llandovery to Wenlock samples reflects the fact that the synorogenic magmatic and metamorphic rocks were exposed to provide detritus. The youngest zircons from the uppermost Silurian strata yield an age of 425 Ma, which approximates the inferred depositional age. This age, together with available biostratigraphic data, indicates that the foreland basin was formed 448-425 Ma ago. We surmise a possible link between the Wuyi-Yunkai orogen and the Appalachian-Caledonian orogen based on the geological constraints and palaeomagnetic data.