Recognition of Yanshanian magmatic-hydrothermal gold and polymetallic gold mineralization in the Laowan gold metallogenic belt,Tongbai Mountains: New evidence from structural controls,geochronology and geochemistry |
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| Institution: | 1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;2. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;3. Third Geological Survey Team, Henan Bureau of Geo-exploration and Mineral Development, Xinyang 464000, China;1. Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves, 9500, Bairro Agronomia, 91501-970 Porto Alegre, Rio Grande do Sul, Brazil;2. Departamento Nacional de Produção Mineral, Superintendência do Mato Grosso do Sul, Rua General Odorico Quadros, 123, 79020-260 Campo Grande, Mato Grosso do Sul, Brazil;3. Geological Survey of Brazil (CPRM), SUREG-GO, Rua 148, 485, Setor Marista, 74170-110 Goiânia, Goiás, Brazil;1. State Key Laboratory of Geological Processes and Mineral Resources, Faculty of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;2. Department of Geology, University of Regina, S4S 0A2 Regina, Canada;3. State Agency of Geology and Mineral Resources, Bishkek, Kyrgyzstan;1. Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100085, China;2. Key Laboratory of Tibetan Environment Changes and Land Surface Processes, CAS, Beijing 100085, China;3. Key Laboratory of Continental Collision and Plateau Uplift, CAS, Beijing 100085, China;4. Department of Earth and Atmospheric Sciences, City College of New York, CUNY, New York, NY 10031;5. University of Chinese Academy of Sciences, Beijing 100049, China;1. Guizhou Geological Survey, Bureau of Geology and Mineral Exploration and Development of Guizhou Province, Guiyang 550005, China;2. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;3. Architectural Engineering College, Guizhou Mingzu University, Guiyang 550025, China;4. Department of Resource and Environmental Engineering, Guizhou Institute of Technology, Guiyang, 550003, China;1. State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;2. Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia;3. National Research Center of Geoanalysis, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The Laowan metallogenic belt in China is an important metallogenic belt within the Tongbai orogenic belt, and contains the medium-sized Laowan and Shangshanghe gold deposits, the small Huangzhuyuan lead–zinc–silver–gold deposit and some gold and Cu–Pb occurrences. These deposits are hosted in Mesoproterozoic plagioclase amphibolite (or schist) and mica-quartz schist. The gold ores are mainly quartz veins and veinlets and disseminated altered ores. Subordinate ore types include massive sulfides and breccias. The Laowan gold deposit is characterized by three right-stepping en-echelon fracture-controlled alteration zones that dip gently to the south and includes disseminated, sheeted and stockwork ores. These lodes were formed by the interaction of ore-forming fluid with foliated-to laminated cataclasite within the transpressional faults. The Shangshanghe gold deposit is characterized by parallel ore lodes that dip steeply to the north, and includes quartz veins and breccias in addition to ores in altered wallrocks. These lodes were formed by focusing of fluids into transtensional faults. These ore controlling faults displaced early barren quartz veins 10 m horizontally with a dextral sense of motion. The ore-hosting structures at the Laowan and Shangshanghe deposits correspond to the P and R-type shears of a brittle dextral strike-slip fault system, respectively, which make angles of about 15° and ? 15° to the Laowan and Songpa boundary faults. The ore-controlling fault system post-dated formation of a ductile shear zone, and peak regional metamorphism. This precludes a genetic relationship between hydrothermal mineralization and regional metamorphism and ductile shear deformation. These gold deposits are not typical orogenic gold deposits. The metallogenic belt displays district-scale-zoning of Mo → Cu–Pb–Zn–Ag → Au relative to Songpa granite porphyry dike zone, suggesting the mineralization may be closely related to the granite porphyry. Measured δ34S of sulfides and δ18O and δD of fluid inclusion waters in auriferous quartz also are consistent with a magmatic source for sulfur and ore fluids. The similarity of Pb isotope ratios between the ores and Yanshanian granitoids suggests a similar source. As the age (139 ± 3 Ma) of granite porphyry obtained by zircon U–Pb isotope overlaps the mineralization age (138 ± 1 Ma: Zhang et al., 2008a), the gold and polymetallic metallogenesis of the Laowan gold belt has close spatial, temporal and possibly genetic relationships with Yanshanian high level magmatism. |
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