Geochronology and isotope geochemistry of the Baogutu porphyry copper deposit in the West Junggar region, Xinjiang, China

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• 作者：Ping Shen^a ; ^{pshen@mail.iggcas.ac.cn} ; Yuanchao Shen^a ; Hongdi Pan^b ; Xian-hua Li^a ; Lianhui Dong^a ; ^c ; Jingbin Wang^a ; ^d ; Heping Zhu^a ; Huawu Dai^a ; Weina Guan^a ; ^c
• 关键词：SIMS zircon U&ndash ; Pb ; Molybdenite Re&ndash ; Os ; Biotite 40Ar/39Ar ; Isotopes geochemistry ; Baogutu porphyry copper deposit ; West Junggar region ; China
• 刊名：Journal of Asian Earth Sciences
• 出版年：2012
• 期刊代码：40_13679120
• 类别：ear
• 出版时间：30 April, 2012
• 卷：49
• 期：Complete
• 页码：99-115
• 文件大小：3782 K

摘要

The Baogutu copper deposit, a newly-discovered middle-sized porphyry copper deposit, is located in the West Junggar region of Xinjiang, NW China. Baogutu is associated with a Late Carboniferous intrusive complex that was emplaced into Lower Carboniferous volcano-sedimentary strata. The intrusive complex comprises main-stage diorites and minor late-stage diorite porphyries. Their intrusive activity occurred in 313.0 卤 2.2 Ma to 312.3 卤 2.2 Ma based on U-Pb zircon SIMS analyses. Molybdenite separated from ore-bearing quartz veins yields Re-Os model ages from 309.4 卤 4.4 Ma to 314.1 卤 4.5 Ma with a weighted mean age of 312.4 卤 1.8 Ma. Biotites, separated from fresh diorite and hydrothermal breccias in main-stage diorites, yield ⁴⁰Ar/³⁹Ar plateau ages of 308.26 卤 1.88 and 305.69 卤 1.76 Ma, respectively. These dates obtained from three independent dating techniques constrain the ore-forming age of the Baogutu deposit.

Stable isotopes (H, O, S) and radiogenic isotope (Pb) have been used to discriminate the sources of the ore-forming fluid at Baogutu. The 未¹⁸O (1.14-1.74鈥? and 未D (鈭?4鈥?to 鈭?8鈥? data indicate that the water of the ore-forming fluids was derived from magmatic water. The 未³⁴S values (鈭?.24鈥?to +0.4鈥? show that the sulfur isotope composition of the ore fluids is characterized by magma sulfur. Lead isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 17.92-18.89, ²⁰⁷Pb/²⁰⁴Pb = 15.45-15.62, ²⁰⁸Pb/²⁰⁴Pb = 37.68-38.36) indicate that the lead of the ore fluids is derived from the mantle. These data confirm the occurrence of a Cu-Au-Mo mineralizing event at Late Carboniferous in the Baogutu region and the ore-forming fluids are mainly derived from the mantle. The event is inferred to be associated with Late Carboniferous Junggar oceanic crust subduction.