Zircon U-Pb ages and Hf isotopic compositions of the granites from Bayanwula area and their geological significance

The Bayanwula area is located in the middle part of the Erlian Basin, eastern part of the Central Asian orogenic belt, and hosts some sand-type uranium deposits.In this paper, the authors present two LA-ICP-MS zircon U-Pb ages and Hf isotopic compositions for granites from the study area, which show that the emplacement ages of these granitic rocks are 292±3 Ma and 288±2 Ma.Theses ages are consistent with those of granitic and volcanic rocks occurring in the Bayinbaolige horst of the Bayanwula area.The data obtained by the authors and previously published data indicate that a magma belt consisting of Late Carboniferous-Early Permian granitic and volcanic rocks were developed in the Bayinbaolige horst of the Bayanwula area.Zircon Hf isotopic compositions show that two granite samples have ε_Hf(t)values of +10.6 to +18.2, which are similar to those of the Early Permian granitic rocks located on the Bayinbaolige horst of the study area, indicating that the granites were derived from the partial melting of juvenile lower crust.Integrated with geological data, this study indicates that the formation of the sand-type uranium deposits developed in the upper member of the Saihan Formation was associated with tectonic-magmatism processes that happened in the eastern part of the Central Asian orogenic belt during Phanerozoic, which provided many optimum conditions for these sand-type uranium deposits.