Provenance records of the North Jiangsu Basin,East China:Zircon U-Pb geochronology and geochemistry from the Paleogene Dainan Formation in the Gaoyou Sag

Detailed zircon U-Pb dating and whole-rock geochemical analyses were carried out on the sedimentary rocks of the Paleogene Dainan Formation from Gaoyou Sag in the North Jiangsu Basin,East China.Whole-rock rare earth element characteristics suggest that the provenance was mainly from the Late Proterozoic low-grade metamorphic felsic rocks in the Dabie-Sulu orogenic belt,with the parent rocks probably being the I-type high-potassium granite gneiss.Cathodoluminescence images indicate that most of the detrital zircons are originally magmatic.A few zircons show overgrowths,indicating multiple-episode tectonic events.The U-Pb age distribution patterns of the detrital zircons suggest four main magmatic episodes in the provenance:Late Archean-Early Proterozoic(2450-2600 Ma),Early Proterozoic(1700-1900 Ma),Late Proterozoic(700-850 Ma),and Late Paleozoic-Mesozoic(100-300 Ma).These zircon U-Pb age and whole-rock geochemical results suggest that the sediments of the Dainan Formation were mainly sourced from the recycled orogenic belts within and/or around the North Jiangsu Basin,including the basement of the Yangtze Block,the Neoproterozoic rocks in the Dabie-Sulu orogenic belt,and the Mesozoic igneous rocks in the south part of Zhangbaling Uplift.