Abstract: Located at both sides of the large, NNE trending DamxungLhasa extension fault, the Gulou granitoids belong to part of the Nyainqentanglha granites in the Gangdise tectonic belt. The main rock types include porphyritic granodiorite, porphyritic granite, biotite adamellite and garnet-granitite. Their K-Ar dating age are about 11 Ma, revealing that the Gulou granitoids were formed in the Miocene epoch. The Gulou granitoids are high in SiO₂, Al₂O₃ and K₂O+Na₂O, and are low in FeO+Fe₂O₃, MgO and CaO, showing the features of metaluminous high-K calc-alkaline granites. They are also LREE-rich, HREE-depletion, have obvious Eu negative anomaly; LILE-rich and HFSE-depletion. In the curves of the trace element distribution patterns normalized by the primitive mantle, they are Rb, Th-rich and Nb, Ta, Ba, Sr, Ti-depletion. These Miocene granitoids were interpreted to be formed in a postcollisional tectonic setting and to have a close relationship with the E-W crustal extension. They were resulted from the crustal partial melting related to crustal extension and plateau uplifting post the collisional orogeny.

Key words: Gulou granitoids, geochemistry, tectonic setting, Miocene, Gangdise tectonic belt