 They suggest the head of mantle plume, which sited beneath the South China Block, led to rifting and bimodal magmatism since 825 Ma.The discovery of 825 Ma komatiitic basalts in Yiyang, which is indicative of hot mantle source, provides an indisputable evidence for the presence of a mantle plume.However, there is alternative genesis of komatiites like hydrous melting in the subduction zone.