Detrital Zircon U-Pb Geochronology Characteristics and Geological Significance of the Ebian Group in the Western Yangtze Block

Key words: 
• Meso-Neoproterozoic /
• Ebian Group /
• Detrital zircon /
• Provenance analysis /
• Tectonic setting

Abstract: [Objectives] The Ebian Group in the western Yangtze Block has traditionally been regarded as one of the representative lithostratigraphic units of the late Mesoproterozoic in South China. The sedimentation age and provenance characteristics of Ebian Group can provide important constraints for reconstructing the Meso- Neoproterozoic tectonic evolution of the Yangtze Block under the background of the assembly of the global Rodinia supercontinent. [Methods] In this study, petrological and detrital zircon U-Pb geochronological analyses were conducted on metasedimentary rocks of the Ebian Group. [Results] The detrital zircon ages of two metamorphic fine-grained litharenite sandstones from the Jiadanqiao Formation of the Ebian Group range from 1950 to 900 Ma. The main relative probability peaks are ca. 910 Ma, ca. 1570 Ma, and ca. 1730 Ma, with secondary peaks at ca. 1130 Ma, ca. 1390 Ma, ca. 1840 Ma, and ca. 2500 Ma. The maximum depositional ages are 908 ± 8 Ma (MSWD = 0.10, n = 5) and 905 ± 5 Ma (MSWD = 0.52, n = 9), respectively. [Conclusion] Combining with regional geological data, the depositional age of the Jiadanqiao Formation of the Ebian Group is constrained to be 910~860 Ma. The sediment source was mainly from magmatic rocks in the western Yangtze Block, with a predominant direction towards the south side. It is speculated that the formation occurred during the early Neoproterozoic micro-block assembly and is associated with the global assembly process of the Rodinia supercontinent.