| 西藏邦铺铅锌矿区石英二长斑岩锆石U-Pb年龄、Hf同位素和稀土元素特征及其地质意义 |
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| 关键词:Bangpu LA-ICP-MS zircon U-Pb dating quartz monzonite porphyry Tibet |
| 基金项目:国家973项目(编号: 2011CB403103);青藏专项(编号: 1212011085529) |
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| Zircon U-Pb Ages, Hf Isotope and REE of Quartz Monzonite Porphyry in the Bangpu Pb-Zn Mining Area of Tibet and Their Geological Significance |
| The Bangpu Mo (Cu) polymetallic deposit is a large-size porphyry deposit newly discovered in the Gangdise belt, where there exist many intrusive rocks of different types and stages. The investigation of the Pb-Zn deposit located in the contact zone in the southeast part of the ore district has been very insufficient, in despite of the attention and exploitation paid to it. In this paper, U-Pb dating of LA-ICP-MS zircon and Hf isotopes and trace elements of zircon were used to investigate ore-bearing quartz-monzonite porphyry outcropped in the lead-zinc mining area, and the weighted average age of the 23 zircons 206Pb/238U is (15.43 ± 0.12) Ma (MSWD = 2.7, n = 23), suggesting a Miocene magmatic product. After the completion of the zircon dating, part of the dated zircons were analyzed systematically for the in-situ analysis of Hf isotopes. The 176Hf /177Hf ratio varies in the range of 0.28279–0 .282913, and εHf(t) varies in the range of 0.6 – 5.0. The testing results of Hf isotope and the Hf isotope of geochemical reservoirs and depleted mantle are similar, indicating that the source area or the quartz monzonite porphyry in this area mainly came from the depleted mantle, but in the process of magmatic evolution it was contaminated by the lower crust. The analyses of REE show the depletion of light REE and enrichment of heavy REE as well as the obvious existence of positive Ce anomaly and negative Eu anomaly, suggesting zircons of typical magmatic genesis. The results are consistent with the previous study of the Mo (Cu) mining area, and hence it is inferred that lead-zinc ore and molybdenum (copper) ore are products from the same porphyry system. It is shown that this deposit is somewhat identical with Jiama and Qulong large-size porphyry deposits in the region, with unified geodynamic background and deep magmatic activity. |
| CHEN-Wei,WANG Li-qiang,HU Zheng-hua,LUO Mao-cheng,LENG Qiu-feng,TANG Xiao-qian,WANG Yi-yun,YANG Yi,ZHANG Zhi.2012.Zircon U-Pb Ages, Hf Isotope and REE of Quartz Monzonite Porphyry in the Bangpu Pb-Zn Mining Area of Tibet and Their Geological Significance[J].Acta Geoscientica Sinica,33(4):569-578. |
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