Sm-Nd dating of the protolith of blueschist in the Shuanghu area, Tibet

Abstract: The 40Ar/39Ar age of crossite in blueschist in the Shuanghu area, Tibet, but the age of the protolith of the blueschist is highly controversial. Previously most researchers think that the protolith is earlier than Devonian in age and some researchers even think it to be Meso-and Neoproterozoic in age and call it the Amugang Group. On the basis of 1:100000 mapping and measurements of the section, the authors collected relevant samples and obtained the Sm-Nd isochron ages of 272 ± 7Ma, 268 ± 5.6Ma and 252 ± 4.6Ma for the protolith of the blueschist. On that basis, combined with the regional geological conditions and occurrence of blueschist in the Shuanghu area, it is believed that the age of the protolith of the blueschist is Permian, and the age of the Amugang Group is assigned to Permian and the age of the Qiagelela ophiolite is determined to be late Early Permian. The age dating provides important evidence for the evidence of the Paleo-Tethys in Lungmu Co-Shuanghu.