西藏多不杂斑岩铜金矿钾长石^(40)Ar/^(39)Ar年龄及其地质意义

^(40)Ar/^(39)Ar Dating for K-feldspar from Duobuza Porphyry Copper-gold Deposit in Tibet,China and Its Geological Significance

西藏多不杂斑岩铜金矿是在班公湖—怒江成矿带发现的第一个斑岩型矿床。通过对多不杂矿床蚀变钾长石进行40Ar/39Ar年代学测试获得,蚀变钾长石的坪年龄为(118.31±0.60)Ma,反等时线年龄为(118.30±0.79)Ma,它们代表多不杂矿床钾化蚀变的年龄为119～118 Ma,与成矿年龄同期。多不杂矿床形成的岩浆-热液过程为,由岩浆期(约120Ma)演化至钾化和成矿期(119～118 Ma),再演化至绢英岩化期(118～115 Ma)。

Duobuza porphyry copper-gold deposit is a newly discovered deposit,which is located in the middle of Tibet plateau and in the west of Bangonghu-Nujiang metallogenic belt.K-feldspar from the potassic alteration zone was analyzed by 40Ar/39Ar dating technique,and these results yielded a plateau age of（118.31±0.60） Ma and a reverse isochron age of（118.30±0.79） Ma with initial 40Ar/36Ar=291±17,indicating that potassic alteration age in Duobuza porphyry deposit ranges from 119 to 118 Ma and coincide with the mineralization age（molybdenite Re-Os age,119-118 Ma）.The magmatic-hydrothermal evolution of Duobuza deposit should be from magmatic stage（around 120 Ma） to potassic alteration and mineralization（119-118 Ma）,then to phyllic alteration（118-115 Ma）,and the duration of magmatic-hydrothermal evolution probably persisted 5 million years.