Baogutu copper deposit in Western Junggar area is a mesoscopic porphyry deposit found in recent years. Study on its geochronology will help further understand ore genesis and regional ore-forming pattern. A series of ...Baogutu copper deposit in Western Junggar area is a mesoscopic porphyry deposit found in recent years. Study on its geochronology will help further understand ore genesis and regional ore-forming pattern. A series of small quartz-diorite and granodiorite stocks outcrop at Baogutu area, numbered I―X according to their size. A detailed exploration on Number V stock confirmed it as a mesoscopic scale copper deposit, and various exploration work has been carried out on other stocks with ore-forming evidence. This paper studies geochronology of Number V stock using zircon SHRIMP U-Pb and single mineral K-Ar method. Twenty-five SHRIMP ages yield two 206Pb/238U weighed mean ages of 335.6 ± 7.8 Ma and 311.4 ± 3.3 Ma respectively. The older date is considered to be inherited zircon from either surrounding rock tuff or deep granitoid batholith, whereas the younger date is the formation age of ore-bearing intrusion. K-Ar ages of ore-forming biotites, 296.0 ± 3.7 Ma and 297.3 ± 3.8 Ma, in combination with Re-Os age of molybdenite, 310 Ma, confirm the ore-forming age of 310-296 Ma. Granophyre and dioritic porphyrite dikes cut Number V stock and their K-Ar ages range from 278 to 240 Ma, which confine the lower boundary of the mineralization. The framework of Baogutu ore-forming geochrono-logy can be established based on these data.展开更多
基金Supported by China Geological Survey (Grant No. 1212010630603)National Science and Technology Supporting Program (Grant No. 2006BAB07B08)
文摘Baogutu copper deposit in Western Junggar area is a mesoscopic porphyry deposit found in recent years. Study on its geochronology will help further understand ore genesis and regional ore-forming pattern. A series of small quartz-diorite and granodiorite stocks outcrop at Baogutu area, numbered I―X according to their size. A detailed exploration on Number V stock confirmed it as a mesoscopic scale copper deposit, and various exploration work has been carried out on other stocks with ore-forming evidence. This paper studies geochronology of Number V stock using zircon SHRIMP U-Pb and single mineral K-Ar method. Twenty-five SHRIMP ages yield two 206Pb/238U weighed mean ages of 335.6 ± 7.8 Ma and 311.4 ± 3.3 Ma respectively. The older date is considered to be inherited zircon from either surrounding rock tuff or deep granitoid batholith, whereas the younger date is the formation age of ore-bearing intrusion. K-Ar ages of ore-forming biotites, 296.0 ± 3.7 Ma and 297.3 ± 3.8 Ma, in combination with Re-Os age of molybdenite, 310 Ma, confirm the ore-forming age of 310-296 Ma. Granophyre and dioritic porphyrite dikes cut Number V stock and their K-Ar ages range from 278 to 240 Ma, which confine the lower boundary of the mineralization. The framework of Baogutu ore-forming geochrono-logy can be established based on these data.
