Highly fractionated Late Triassic I-type granites and related molybdenum mineralization in the Qinling orogenic belt: Geochemical and U–Pb–Hf and Re–Os isotope constraints |
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| Institution: | 1. The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, People''s Republic of China;2. State Key Laboratory of Continental Dynamics, Northwest University, Xi''an 710069, People''s Republic of China;3. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, People''s Republic of China;4. Xi''an Institute of Geology and Mineral Resources, Xi''an 710054, People''s Republic of China;1. Key Laboratory of Orogen and Crustal Evolution, Peking University, 5 Yiheyuan Road, Beijing, 100871, China;2. Beijing Institute of Geology for Mineral Resources, Beijing, 100012, China;3. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China;1. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;2. Graduate University of Chinese Academy of Sciences, Beijing, China;3. Geology Department, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1, Canada;4. No.1 geological party Xinjiang Bureau of Geology and Mineral exploration, Changji, 831100, China;5. Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;1. School of Earth Sciences, Lanzhou University, Lanzhou 730000, China;2. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;3. Department of Earth Sciences, Durham University, Durham, DH1 3LE, UK;4. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;1. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. Department of Earth Sciences, Durham University, Durham DH11 3LE, UK;3. School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;4. School of Earth Sciences, Lanzhou University, Lanzhou 730000, China;1. Development Research Center of Chinese Geological Survey, Beijing 100037, China;2. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;3. Beijing Institute of Geology for Mineral Resources, Beijing 100012, China;1. Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Minerals, College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, China;2. Jining Medical University, Jining 272067, China;3. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;4. Beijing Institute of Geology for Mineral Resources, Beijing 100012, China;5. Department of Geology, Juniata College, Huntingdon, PA, USA |
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| Abstract: | We present new data on the highly fractionated Late Triassic I-type Liyuantang granite, which is located in the middle segment of the South Qinling Subzone of central China and is associated with molybdenum mineralization. Zircon U–Pb dating indicates that the granite was emplaced at 210.1 ± 1.9 Ma, with a single zircon containing an inherited core that yielded an age of 449.8 ± 7.1 Ma. Magmatic zircons from the granite have εHf(t) values of ? 4.0 to + 1.5, whereas the inherited zircon core has a εHf(t) value of ? 5.3. Calculated Hf model ages of crust formation are indicative of substantial contributions from melting of Proterozoic crust that ranges in age from 1501 to 1155 Ma. The granite contains high concentrations of Si, Al, Na, and K, is enriched in Rb, Th, and U, has elevated Rb/Sr and Ga/Al ratios, and is depleted in Ti, Fe, Mn, Mg, Ca, and P, with significantly negative Eu anomalies (δEu = 0.33–0.50), similar to other highly fractionated I-type granites. These data indicate that the magmas that formed the Liyuantang pluton were produced during partial melting of Proterozoic garnet-absent quartz amphibolites. The magmas then fractionated apatite, feldspar, Ti-bearing phases, biotite, and hornblende prior to emplacement.Re–Os isotope analysis of molybdenite from the study area yields a mineralization age of 200.9 ± 6.2 Ma, suggesting that the Liyuantang molybdenum deposit formed during a previously unrecognized mineralization event. The present results, together with previous data, demonstrate that highly fractionated I-type granites associated with the second pulse of magmatism in the South Qinling subzone should be considered highly prospective for mineral exploration, focusing on Triassic–Early Jurassic granitoids. |
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