Geological Party No. 243, CNNC, Chifeng 024000, Inner Mongolia, China

 The Baoligaomiao Formation, located in the Arshan area of the Da Hinggan Ling (Mts. ), compri? ses a continental sedimentary?volcanic rock series, predominantly formed of sedimentary clastic rocks and andes? ites, which have undergone regional metamorphism and have been converted into the low greenschist facies. This study focuses on the zircon U??Pb dating and geochemical analysis of the low?grade metamorphic rocks of Baoligao? miaoFormation. By integrating lithologic petrographosed and metamorphic deformation characteristics, the research aims to reconstruct the protolith structure and explore the sedimentary setting. The results indicate that the LA?? ICP??MS zircon U??Pb age of the metamorphic andesites in the Arshan area is approximately (312. 1 ± 1. 2) Ma, belonging to the Late Carboniferous and Early Permian periods, and it is identified as part of Baoligaomiao Forma? tion. The protolith assemblage of Baoligaomiao Formation in the Arshan area is a typical terrigenous intermediate? acidic volcano?sedimentary lacustrine facies. The sedimentary tectonic environment is the intra?arc basin of the ac? tive continental margin, which is consistent with the tectonic environment of the Late Carboniferous??Early Permianin Erlian ??Hegenshan ophiolite?accretionary complex.