关键词: 合肥盆地, 碎屑锆石定年, 物源分析, 张八岭隆起

Abstract: The Hefei Basin in southeastern North China block was formed during the collision between the South and North China blocks. It transformed from a foreland basin, developed by northward thrusting of the Dabie Orogen, into a fault subsidence basin in an extensional tectonic setting in the Early Cretaceous. The Middle Jurassic Yuantongshan Formation in the Hefei foreland strata features lacustrine facies, which is very different from fluvial facies within the Lower Jurassic Fanghushan Formation. In order to obtain detailed provenance information, we performed detrital zircon LA-ICP MS U-Pb dating of purple siltstone from the Yuantongshan Formation, Feixi district. Zircon dating results of two collected samples revealed two major age peaks at ~2.0 Ga and ~770 Ma and one minor peak at ~2.4 Ga. Histograms of detrital zircon ages for the Yuantongshan Formation and Yangtze block are almost identical, suggesting that the later is provenance of the former. Considering that provenance of strata in a basin should not originate from other side of a watershed, provenance of the Yuantongshan Formation, therefore, is likely rocks cropping out in the Zhangbaling Uplift in the Middle Jurassic. In the early period of the Yanshanian movement, a fold-and-thrust belt occurred in the Lower Yangtze region. The Zhangbaling Uplift raised significantly at that time, causing surface rocks to erode while only the Zhangbaling Group and Feidong Complex preserved. Materials eroded from the Zhangbaling Uplift were transported to and deposited in the Hefei Basin to form the Yuantongshan Formation.

Key words: Hefei Basin, detrital zircon dating, provenance analysis, Zhangbaling Uplift