Geochronological and mineralogical constraints on mineralization of the Hetai goldfield in Guangdong Province,South China |
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| Affiliation: | 1. CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Department of Geology, University of Regina, Regina S4S 0A2, Canada;1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. Guangxi Museum of Nationalities, Nanning, Guangxi 530022, China;3. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China;4. Key Laboratory of Vertebrate Evolution and Human Origin of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China;5. University of Chinese Academy of Sciences, Beijing 100049, China;1. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China;4. Center for Earth Environment & Resources, Sun Yat-sen University, Guangzhou 510275, China;5. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;6. Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;2. CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;3. Department of Geology, University of Regina, Regina S4S 0A2, Canada;4. Team 402, Hunan Geology and Mineral Resources Exploration and Development Bureau, Changsha 410014, China;1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China;2. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China;3. Seismological Bureau of Sichuan Province, Chengdu 610041, China;4. State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;5. Sichuan Changning Natural Gas Development Co., Ltd, Chengdu 610000, China;1. School of Earth Sciences, Lanzhou University, Lanzhou 730000, China;2. Key Laboratory of Mineral Resources in Western China (Gansu Province), Lanzhou 730000, China;3. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, CAGS, Beijing 100037, China;1. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;4. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China |
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| Abstract: | The Hetai goldfield, located in the southern segment of the Qinzhou Bay-Hangzhou Bay Juncture Orogenic Belt (QHJB), is the largest concentration of gold deposits in Guangdong Province, South China. The gold mineralization is hosted within the late Neoproterozoic to early Paleozoic Yunkai Group and strictly confined to mylonite (ductile shear) zones. The nature of the structural control of mineralization, in particular the role of ductile versus brittle deformation and their ages, which remain unclear despite numerous previous studies, are examined in this paper through an integrated study of geochronology and mineralogy.Lamellar and filament structures shown by pyrite and pyrrhotite in the ores suggest that sulfidation took place during ductile deformation and syntectonic metamorphism, but the majority of the ores are associated with brittle deformation features. In combination with macroscopic and microscopy observations on shear fabrics, LA-ICP-MS U-Pb dating on zircons of hydrothermal origin from mylonites suggests that the Hetai goldfield was subjected to two shearing events: an early sinistral ductile shearing at ca. 240 Ma, and a late dextral ductile-brittle shearing at ca. 204 Ma (Indosinian). These ages are ca. 90–30 Ma older than the previously published gold mineralizing ages of ca. 175–152 Ma (Yanshanian), suggesting that the main gold mineralization and related brittle deformation significantly postdate the ductile deformation. This inference is supported by the mineralization temperatures estimated from geothermometers of arsenopyrite (ca. 350–290 °C), chlorite (ca. 260–230 °C), and sphalerite (ca. 230–170 °C) intergrown with native gold, which are considerably lower than that for the ductile deformation (500–300 °C or higher). Based on these data, we propose that the gold mineralization in the Hetai goldfield predominantly occurred during the Yanshanian event, and only minor gold mineralization and associated sulfidation took place during the earlier Indosinian ductile deformation. |
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| Keywords: | LA-ICP-MS U-Pb dating Hydrothermal zircon Mineral geothermometry Mylonite (ductile shear) zone Hetai goldfield South China |
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