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

Abstract

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 (2450–2600Ma), Early Proterozoic (1700–1900Ma), Late Proterozoic (700–850Ma), and Late Paleozoic–Mesozoic (100–300Ma). 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.