引用本文：李振生,赵卓娅,李建勋,李全忠,张交东,牛浩.2018.华北克拉通东南缘寒武系底部黑色碎屑岩系的物源分析及其对晚前寒武纪地质演化的约束[J].地质学报,92(9):1803-1828. LI Zhensheng,ZHAO Zhuoya,LI Jianxun,LI Quanzhong,ZHANG Jiaodong,NIU Hao.2018.Provenance Analysis of the Black Clastic Rock Series at the Cambrian Base in the Southeastern Margin of North China Craton and Its Constraints on the Late Precambrian Geologic Evolution[J].Acta Geologica Sinica,92(9):1803-1828.
Provenance Analysis of the Black Clastic Rock Series at the Cambrian Base in the Southeastern Margin of North China Craton and Its Constraints on the Late Precambrian Geologic Evolution
Abstract:The sequence division, sedimentary age and provenance of the black clastic rock series called Madian Formation (or Fengtai Formation) between Neoproterozoic and Cambrian dolomites in the southeastern margin of North China Craton (NCC) are still debated. In this study, comprehensive analysis using elemental geochemistry and detrital zircon U-Pb geochronology has provided important evidence for stratigraphic framework and Meso Neoproterozoic to Early Paleozoic tectonic evolution of the southeastern margin of NCC. The enrichment coefficients (EF) of most elements and U-Pb ages of detrital zircons of the whole Madian Formation are similar, and the latter mainly concentrated between 2.6 Ga and 1.0 Ga with multiple age peaks of ~2.5 Ga, ~2.1 Ga, ~1.8 Ga, 1.6~1.4 Ga and 1.3~1.0 Ga. The Madian Formation is generally considered a continuous transgressive stratum of the Cambrian series 2 epoch in the passive continental margin, with sediments entirely derived from the Xuhuai area in the interior of the North China Craton. The Madian Formation is characteristic of two-ends mixing between Neoproterozoic carbonatic sedimentary caprocks and early Precambrian metamorphic basements, manifested by difference of petrology, element geochemistry and provenance. Detrital zircons of >18 Ga were derived from the Early Precambrian metamorphic basement, while the Mesoproterozoic detrital zircons and gravel grade dolomite debris clastic particles were from the Neoproterozoic sedimentary caprocks, with a very small amount of Neoproterozoic detrital zircons from the Neoproterozoic basic dykes. 1.6~1.4 Ga and 1.3~1.0 Ga detrital zircon records in the Neoproterozoic and lower Paleozoic of the periphery of NCC confirm that a Meso-Neoproterozoic tectonic belt developed at least in the eastern and southern margins of NCC, which are similar to those in the North Qinling region and was strongly involved in the process of Columbia supercontinent breakup and Rodinia supercontinent convergence during the Mesoproterozoic era.
The tectonic belt was the main provenance supply area for rift basins in the eastern to southern margin of NCC during early Neoproterozoic era, and started breaking up from NCC at 900Ma so that its provenance proportion has been completely missing in Early Paleozoic Madian formation deposition.
