Metallogenic age and hydrothermal evolution of the Jidetun Mo deposit in central Jilin Province,northeast China: Evidence from fluid inclusions,isotope systematics,and geochronology |
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| Institution: | 1. College of Earth Sciences, Jilin University, Changchun 130061, China;2. Institute of Geology, Chinese Academy of Geological Science, Beijing 100037, China;1. CSIRO, Mineral Resources, Discovery Program, Kensington 6151, Western Australia, Australia;2. Centre for Exploration Targeting, University of Western Australia, Crawley 6009, Western Australia, Australia;3. Sandfire Resources Ltd., West Perth 6005, Western Australia, Australia;1. Laboratory of Isotope Geology, MLR, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China;2. Laboratory of Metallogeny and Mineral Assessment, MLR, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, PR China;1. Chengdu Institute of Geology and Mineral Resources, Chengdu 610081, China;2. Tibet Institute of Geological Survey, Lhasa 850000, China;3. Geological Team 5 of the Tibet Bureau of Geology and Mineral Exploration and Development, Golmud, Qinghai 816000, China;1. Key Laboratory for Evolution of Past Life and Environment in Northeast Asia (Jilin University), Ministry of Education, Changchun 130026, China;2. Research Center of Paleontology and Stratigraphy, Jilin University, Changchun 130026, China;3. Wuxi Research Center of Petroleum Geology, SINOPEC, Wuxi 214126, China;4. Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China;5. College of Earth Sciences, Jilin University, Changchun 130061, China;1. College of Earth Sciences, Jilin University, Jianshe Str. 2199, Changchun 130061, Jilin, China;2. Department Geology and Geography, University of Salzburg, Hellbrunner Str. 34, Salzburg A-5020, Austria;3. State Key Laboratory of Continental Dynamics, Northwest University, Northern Taibai Str. 229, Xi’an 710069, Shaanxi, China;4. Shenyang Institute of Geology and Mineral Resource, Northern Huanghe Str. 2, Shenyang 110034, Liaoning, China;5. Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, School of Earth and Space Sciences, Peking University, Yiheyuan Str. 5, Beijing 100871, China;1. CODES, Centre of Excellence in Ore Deposits, University of Tasmania, Private Bag 79, Sandy Bay, Hobart, TAS 7001, Australia;2. AIRIE Program, Department of Geosciences, Colorado State University, Fort Collins, CO 80523-1482, USA;3. CEED, Centre for Earth Evolution and Dynamics, PO Box 1048, University of Oslo, Norway;4. Sandfire Resources NL, PO Box 1495, West Perth, WA 6872, Australia |
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| Abstract: | The Jidetun deposit is a large porphyry Mo deposit that is located in central Jilin Province, northeast China. The Mo mineralization occurs mainly at the edge of porphyritic granodiorite, as well as the adjacent monzogranite. Field investigations, cross-cutting relationships, and mineral paragenetic associations indicate four stages of hydrothermal activity. To determine the relationships between mineralization and associated magmatism, and better understand the metallogenic processes in ore district, we have undertaken a series of studies incluiding molybdenite Re–Os and zircon U–Pb geochronology, fluid inclusions microthermometry, and C–H–O–S–Pb isotope compositions. The molybdenite Re–Os dating yielded a well-defined isochron age of 168.9 ± 1.9 Ma (MSWD = 0.34) that is similar to the weighted mean 206Pb/238U age of 173.5 ± 1.5 Ma (MSWD = 1.8) obtained from zircons from the porphyritic granodiorite. The results lead to the conclusion that Mo mineralization, occurred in the Middle Jurassic (168.9 ± 1.9 Ma), was spatially, temporally, and genetically related to the porphyritic granodiorite (173.5 ± 1.5 Ma) rather than the older monzogranite (180.1 ± 0.6 Ma). Fluid inclusion and stable (C–H–O) isotope data indicate that the initial H2O–NaCl fluids of mineralization stage I were of high-temperature and high-salinity affinity and exsolved from the granodiorite magma as a result of cooling and fractional crystallization. The fluids then evolved during mineralization stage II into immiscible H2O–CO2–NaCl fluids that facilitated the transport of metals (Mo, Cu, and Fe) and their separation from the ore-bearing magmas due to the influx of abundant external CO2 and heated meteoric water. Subsequently, during mineralization stage III and IV, increase of pH in residual ore-forming fluids on account of CO2 escape, and continuous decrease of ore-forming temperatures caused by the large accession of the meteoric water into the fluid system, reduced solubility and stability of metal clathrates, thus facilitating the deposition of polymetallic sulfides. |
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| Keywords: | Jidetun deposit Fluid inclusions H–O–C–S–Pb isotope Molybdenite Re–Os Zircon U–Pb Central Jilin Province |
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