DETERMINATION OF THE BAIYINGAOLAO FORMATION IN WUNUER AREA, DAXINGANLING MOUNTAINS: Geological Implication

A large number of Mesozoic volcanic rocks are developed in Daxinganling Mountains of Northeast China, among which the Early Cretaceous volcanic rocks serve as an important part. The stratigraphic attribution and tectonic setting of the Early Cretaceous volcanic rocks of the early stage are controversial currently. Taking the Early Cretaceous rhyolites in Wunuer area of Daxinganling Mountains as the study object, the authors carry out the zircon U-Pb dating and lithogeochemical determination. The results show that the LA-ICP-MS zircon U-Pb age is 134.3±1.8 Ma, indicating the early Early Cretaceous. According to rock association and spatiotemporal distribution, the rhyolites are assigned to Baiyingaolao Formation. The lithogeochemical analysis indicates that the rhyolites in the area belong to high-Si high-K weak peraluminous calc-alkaline series, characterized by enrichment of LILEs(K, Rb and Ba), and depletion of Sr and HFSEs(Nb, P and Ti), relative enrichment of LREEs and depletion of HREEs, with moderate negative Eu anomaly. Combined with the regional geological background and previous research results, it is concluded that the Baiyingaolao Formation in Wunuer area was formed in the volcanic arc setting related to the westward subduction of Paleo-Pacific Ocean.