⁴⁰Ar/³⁹Ar Ages of the Da Lien Granite Related to the Nui Phao W Mineralization in Northern Vietnam

Abstract 40 Ar/ 39 Ar dating was conducted on the Da Lien granite related to greisen‐skarn type polymetallic (W‐CaF 2 ‐Cu‐Bi‐Au) mineralization in Nui Phao, northern part of Vietnam in the South China Plate. Biotite and muscovite separates from the biotite‐muscovite granite and greisenized granite indicate four plateau ages: 82.2 ± 0.4 Ma, 82.8 ± 0.3 Ma, 81.5 ± 0.3 Ma and 82.5 ± 0.4 Ma. The plateau ages were not significantly influenced by excess 40 Ar in dated minerals or by loss of radiogenic 40 Ar due to hydrothermal activities. The results indicate that solidification of granite related to the polymetallic mineralization occurred in the Late Cretaceous between 82.8 Ma and 81.5 Ma.