The protolith of the studied amphibolite is ortho-plagioclase amphibolite, with the geochemical characteristics of tholeiite series basic volcanic rocks. The chondrite-normalized REE patterns are rightward inclined and the primitive mantle normalized trace element spidergrams are characterized by enriched Rb, Ba, Nb and Ta and depleted Sr, Th and U. High resolution LA-ICP-MS in situ dating yields the age of (863±10) Ma for gneissic amphibolite in Nyainrong Rock Group located in Nyainrong microblock, northern Nagqu County, Tibet, which indicates the protolith age of basic volcanic rocks and further restricts the formation age of Nyainrong rock group.