Abstract: Plagiogranite was recognized for the first time in the Goicang ophiolites in Xizang. The examination of geology, petrology, lithochemistry and geochemistry has disclosed that the plagiogranite may be allocated to the abnormal oceanicridge granites. The mantle-derived magmas are the same as those of metamorphic peridotite, basic dykes and basic lava. The plagiogranite as the relicts from the basic-ultrabasic magmatic differentiation should be assigned to the light-coloured rocks and member rocks in the Goicang ophiolites.