~40Ar/~39Ar neutron activation ages of quartz from the Jinman vein copper deposit in western Yunnan and their significance

摘要

Quartz samples collected from the Jinman vein copper deposit in the Lanping Basin of western Yunnan were determined by ~40Ar/~39Ar fast neutron activation techniques, and the spectra are characterized as being saddle-shaped. The samples yielded a plateau age of 58.05± 0.54 Ma, a minimum appearance age of 56.76±0.81 Ma and an isochron age of 54.30± 0.15 Ma, the three ages being close to each other, indicating that the ages of the quartz sam- ples so far determined are true and reliable. The plateau age represents the time of formation of Cu-bearing quartz veins, which is corresponding to Early Himalayan.