Geological, geochronological, geochemical, and Sr–Nd–O–Hf isotopic constraints on origins of intrusions associated with the Baishan porphyry Mo deposit in eastern Tianshan, NW China

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• 作者：Yinhong Wang ; Chunji Xue ; Jiajun Liu ; Fangfang Zhang
• 关键词：Zircon U–Pb age ; Molybdenite Re–Os dating ; Sr–Nd–O–Hf isotopes ; Baishan porphyry Mo deposit ; Eastern Tianshan
• 刊名：Mineralium Deposita
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：51
• 期：7
• 页码：953-969
• 全文大小：6,405 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Geology
  Mineral Resources
  Mineralogy
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-1866
• 卷排序：51

文摘

The Baishan porphyry Mo deposit (0.72 Mt; 0.06 % Mo) is located in the interior of the eastern Tianshan orogenic belt in Xinjiang, NW China. The deposit comprises 15 orebodies that are associated with monzogranite and granite porphyry stocks and are structurally controlled by roughly EW-trending faults. Secondary ion mass spectrometry (SIMS) zircon U–Pb dating of the monzogranite and granite porphyry yielded the Middle Triassic age (228 ± 2 to 227 ± 2 Ma), which coincide with the molybdenite Re–Os model ages ranging from 226 ± 3 to 228 ± 3 Ma. The Triassic monzogranite and granite porphyry belong to high-K calc-alkaline series and are characterized by high SiO<sub>2sub> and Al<sub>2sub>O<sub>3sub> and low MgO, TiO<sub>2sub>, and P<sub>2sub>O<sub>5sub> concentrations, with negative Eu anomalies (δEu = 0.55–0.91). The least-altered monzogranite and granite porphyry yield uniform ε<sub>Ndsub>(t) values from +1.6 to +3.6, and wide (87Sr/86Sr)<sub>isub> ratios ranging between 0.7035 and 0.7071, indicating that they were derived from the lower crust. In situ O–Hf isotopic analyses on zircon using SIMS and laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) indicate that the δ18O and ε<sub>Hfsub>(t) values of zircon from a monzogranite sample vary from 6.1 to 7.3 ‰ and +8.0 to +11.7, respectively, whereas zircon from a granite porphyry sample vary from 6.2 to 6.9 ‰ and +7.3 to +11.2, respectively. The geochemical and isotopic data imply that the primary magmas of the Baishan granite were likely derived from partial melts from the lower crust involving some mantle components. The Baishan Mo deposit and granitic emplacement were proposed to be most likely related to post-orogenic lithospheric extension and magmatic underplating. An extensional event coupled with the rising of hot mantle-derived melts triggered partial melting of the lower crust, as well as provided metals (Mo).