This paper works on the metavolcanites as thin layers in the thick metasedimentary rocks of the Laochanghe Formation. The results show that the starting age of the Dahongshan Group is advanced to (1 711±4) Ma which confirms again the existence of the old crystalline basement in western Yangtze Block, and that there was a metamorphic event around ～850 Ma in the Neoproterozoic which must be a regional metamorphism related to the Neoproterozoic magmatism.