Subduction of the Paleo Pacific Plate at the southeast edge of the South China Block during the Early to Middle Jurassic: Sedimentary records from Fujian Province

Abstract

During the Mesozoic, the tectonic evolution of the southeastern margin of the South China Block was mainly influenced by the subduction of the Palaeo-Pacific Plate. The sedimentary basins along the southeastern margin of the South China Block have preserved the sedimentary record of this process. In this paper, the sedimentary rocks of the Lishan Formation and Zhangping Formation in the Zhangping area of the southeastern margin of the South China Block are studied in terms of sedimentology, petrography, lithogeochemistry, U–Pb chronology of detrital zircon, and zircon trace elements. The study shows that the detrital zircon U–Pb age of the Lishan Formation is 2965–202 Ma, with two major age groups: 253–220 Ma and 1925–1799 Ma; the detrital zircon U–Pb age of the Zhangping Formation is 2587–190 Ma, with two major age groups: 246–234 Ma and 1929–1861 Ma; the ancient sediments in the samples are affected by recycle, and the Early Jurassic source area in the study area is an acidic magma zone, while the Middle Jurassic source area is located in a moderately acidic magma zone and recycle body; the Early Jurassic Lishan Formation and Middle Jurassic Zhangping Formation are mainly derived from the Wuyi Massif. In the upper section of the Lishan Formation, the secondary age groups of ca.448 and ca.773 Ma occur, and the detrital zircons in this section are mainly from the Jiangnan orogenic belt. The ongoing subduction of the Paleo-Pacific Plate led to the formation of diverse back-arc basins within the region; during the Early Jurassic, it was a back-arc compressional basin, transitioning into a back-arc extensional basin during the Middle Jurassic.