Depositional age of the Dagushi Group in the Dahong Mountain, Hubei Prov-ince:Evidence from U-Pb ages of detrital zircons

The Dagushi Group, spread on the northern margin of the Yangtze Craton, is a well-preserved succession of the Mesopro-terozoic strata in South China, unconformably overlain by the Huashan Group.It is generally considered to have the same age as the Shennongjia Group.However, the isotopic geochronological evidence of material source is relatively insufficient.Detrital zircon UPb dating results of sandstone from Taiyangsi Formation on the bottom of Dagushi Group are first reported in this paper.The dating re-sults demonstrate that the oldest and youngest ages are 3.1~3.2Ga and 1124Ma, respectively.There are two age peaks of 2.65Ga and 2.75Ga in the detrital zircon.Its detrital zircon ages are consistent with the multi-period magmatic activities in Kongling Complex and Yangpo Complex before Neoproterozoic.Nevertheless, the Shennongjia Group, widely distributed in western Hubei Province, was deposited from 1.4Ga to 1.1Ga with three age peaks of 1.6Ga, 2~2.1Ga and 2.7~2.8Ga.These data indicate that the Dagushi Group was deposited obviously later than the Shennongjia Group, and hence they do not belong to the same stratigraphic sequence.