The oldest Mo porphyry mineralization in the Yangtze Valley Metallogenic Belt of eastern China: Constraints on its origin from geochemistry,geochronology and fluid inclusion studies at Matou |
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| Institution: | 1. South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 Xingang Street, Guangzhou 510301, China;2. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Wushan, Guangzhou 510640, China;3. College of Resource and Metallurgy, Guangxi University, Nanning, Guangxi 530004, China;4. University of Chinese Academy of Sciences, Beijing 100049, China;5. Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China;1. School of Earth Sciences, Zhejiang University, 38 Zheda Road, Hangzhou, Zhejiang 310027, China;2. Earth Dynamic Research Group, The Institute for Geoscience Research (TIGeR) and ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), Department of Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia;3. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China;1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;2. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;3. Department of Earth and Atmospheric Sciences, Indiana University, Bloomington, IN 47405, USA |
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| Abstract: | The Matou Mo(-Cu) deposit, located in the Yangtze Valley Metallogenic Belt of central-eastern China, is a typical porphyry-type Mo deposit. The orebodies at the deposit are hosted by Matou porphyritic granodiorite, which is the largest intrusive in the area. Quartz vein-type and disseminated sulfide mineralization are well developed in the porphyry and near its contact with Silurian sandstone. Crosscutting relationships indicate that porphyritic granodiorite is the oldest phase in the pluton, which is crosscut by a porphyritic diorite containing traces of chalcopyrite, and later dolerite dykes. These phases have U-Pb zircon dates of 147 ± 3, 140 ± 1 and 135 ± 1 Ma, which confirms the cross-cutting relationships observed in the field. A Re-Os molybdenite isochron age of 147 ± 4 Ma indicates that the porphyritic granodiorite is the source of the oldest Mo mineralization in the metallogenic belt and was formed during a change of the tectonic setting in the area, from an intracontinental orogeny to extensional tectonics. From 147 to 135 Ma, crust-mantle interaction played an important role in the formation of magmatic rocks at Matou. Systematic petrological and geochemistry investigations reveal that the three phases have a crust source with minor input from the mantle. Investigation of ore-forming fluid, H-O isotopes, S isotopes, and the Re content of molybdenite indicate that the ore-forming fluid and metals were derived from the lower crust. During the evolution of fluid from initial magmatic fluids (stage I) to ore-forming fluids (stage II), fluid boiling accompanied by the input of relatively cooler meteoric water led to the deposition of the Mo mineralization. |
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| Keywords: | Yangtze Valley Metallogenic Belt Matou Oldest Mo porphyry mineralization Fluid boiling Crust-mantle interaction |
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