Isotopic Dating of the Nyainqentanglha Granite and Its Significance

The Nyainqentanglha granite, a batholith with an area of 1500 km2 in the central Lhasa block, comprises mainly of medium-fine-grained biotite monzonitic granite and medium-coarse-grained biotite monzonitic granite. K-Ar dating, Rb-Sr dating, SHRIMP U-Pb dating of representative samples of the batholith shows that the crystallization age of the medium-fine-grained biotite monzonitic granite is 8.49±0.14 Ma, 8.07±0.35Ma and 8.70±1.40 Ma, 18.3±0.4 Ma and that of the medium-coarse-grained monzonitic granite is 9.80±0.35 Ma, 9.33±0.41 Ma, 11.01±0.24 Ma. The emplacement and crystallization of the Nyainqentanglha granite, the youngest granite batholith ever known inside the Lhasa block, have a close relationship with the collisional orogeny, crustal thickening, plateau uplifting, E-W crustal extension and have a dynamic genetic relationship with the crustal partial melting.