LA-ICP-MS zircon U-Pb geochronology of the tuffs on the uppermost of the Emeishan basalt succession in Panxian County,Guizhou Province:Constraints on genetic link between Emeishan large igneous province and the mass extinction

In 1990s,some researchers suggested a temporal link between volcanism of the Emeishan Large Igneous Province(ELIP) and the mass extinction at the Permian-Triassic Boundary(P-TB),and were supported by the 40Ar/39Ar isotopic dating showing that the ELIP formed in the Late Permian.However,in recent years,a quantity of SHRIMP U-Pb datings suggested that the large-scale volcanism erupted at ~260Ma.Hence,the ELIP volcanism has been attributed to be the cause of the end-Guadalupian mass extinction in the Middle Permian.In contrast,the intense volcanism in Siberian traps has been considered to be the main cause of the P-T boundary great mass extinction which has been ascribed to a global environmental change due to voluminous gases and volcanic ash production.Recently,we have found a ~100m thick tuff layer in the uppermost of Emeishan basalt succession in the Panxian County,Guizhou Province,the eastern ELIP.Our new LA-ICP-MS zircon U-Pb dating on tuff from the uppermost of the Emeishan basalt succession yields an average age of 251.0±1.0Ma,coeval to those from ash or clay beds in the P-TB of the Meishan section in Zhejiang Province.Consequently,the end of the Emeishan flood volcanism is consistent with the main pulse of the P-TB Siberian large igneous province.Thus,our new dating result provides us a clue of a cause-and-effect relationship between the Emeishan large igneous province and the largest mass extinction in the earth's history(P-TB).