Thermochronology of the monzonitic granite related to the Hutouya Cu-Pb-Zn polymetallic deposit in Qiman Tage, Qinghai Province

The Hutouya mining area in Qiman Tage of Qinghai Province owns the characteristics of inner-and exo-contact belt skarn subtype mineralization. The magmatic intrusive activities are strong in this area. The carbonatite formation of different ages is exposed extensively. The combination of metal metallogenic elements is complex. The potential for the ore prospecting is great. This study is based on the thermochronology theory for rock bodies. The total energy of rock bodies is proportional to its scale. The thermal energy is larger as the scale of rock bodies is larger, the thermal effect is larger as the thermal energy is larger, and the cooling rate is larger as the thermal effect is larger. The cooling rate is calculated via the closure temperature of different minerals. The authors studied Ar-Ar ages of biotite and plagioclase from the Hutouya mining area. The ⁴⁰Ar-³⁹Ar plateau ages of biotite and plagioclase from the HTY002 monzonitic granite sample related to mineralization are 2(33.6 ±2.2) Ma and (231.5 ±1.3) Ma, respectively. The ⁴⁰Ar-³⁹Ar plateau ages from the HTY016 sample are (229.6±2.3) Ma and (219.3±1.8) Ma, respectively. The ⁴⁰Ar-³⁹Ar plateau ages of the HTY019 sample are (224.7±2.6) Ma and (222.2±2.2) Ma, respectively. The calculated cooling rates are 57.14℃/Ma, 11.65℃/Ma, and 48.00℃/Ma. Where the compositions of the intrusive rocks are similar, the differences of the unit thermal energies of their emplacement are very small. Because the total energy of rock bodies is proportional to its scale, the total energies of rock bodies of different scales are different. The thermal energy of large rock bodies is large, the time of balance with the surrounding rock is long, the thermal effect is large, and the cooling rate is low. The cooling rates of different minerals from the Hutouya mining area are similar. The values of the cooling rates are high, varying from 11 to 57℃/Ma, so the thermal effect is large. It is thus concluded that the potential for the ore prospecting is great in the Hutouya mining area.