山西义兴寨金矿是五台山—恒山金矿集区内最为典型的金矿床,也是山西省最大的金矿床。近年来,在矿区河湾斑岩体的深部探矿过程中发现了一个大型蚀变斑岩型金矿体(>20 t Au)。然而,关于该蚀变斑岩金矿体的成因还缺乏相关的研究,因而...山西义兴寨金矿是五台山—恒山金矿集区内最为典型的金矿床,也是山西省最大的金矿床。近年来,在矿区河湾斑岩体的深部探矿过程中发现了一个大型蚀变斑岩型金矿体(>20 t Au)。然而,关于该蚀变斑岩金矿体的成因还缺乏相关的研究,因而制约了对该矿床深部及外围勘探工作的开展。本文通过对蚀变斑岩的锆石开展了LA–ICPMS原位的U–Pb同位素分析,结果表明蚀变石英斑岩的侵位时间为141±1 Ma,从而限定了蚀变斑岩金矿化的时间在131-141 Ma之间。对硫化物石英脉和蚀变斑岩型金矿石系统的元素地球化学分析结果表明两种类型矿石具有相似的特征,进而提出蚀变斑岩型金矿化与脉状金矿是同期成矿流体作用的结果。展开更多
The morphology, REE geochemistry and U-Pb geochronology of zircons from quartz monzodiorite in the Sunzhuang area, Fanshi County, Shanxi Province are presented in this study. The zircon crystals can be classified into...The morphology, REE geochemistry and U-Pb geochronology of zircons from quartz monzodiorite in the Sunzhuang area, Fanshi County, Shanxi Province are presented in this study. The zircon crystals can be classified into four main types as： AB, L, S and P, and 24 subtypes such as AB4, ABs, Ls, and S3. The maximum crystallization temperature of zircon was estimated as 850℃, with the minimum of 550℃. The peak temperatures of the zircon crystallization range from 650℃ to 700℃. The abundances of Th and U in the zircon grains show large variation with the Th/U values 〉 0.4. The Th and U values also show a positive correlation in most zircons. The REE abundance of zircon in the quartz monzodiorite ranges from 280.4 ppm to 2143 ppm with an average of 856.4 ppm. The chondrite normalized zircon REE patterns show two types, one is characterized by HREE enrichment and LREE depletion with positive Ce-anomaly and negative Eu-anomaly whereas the other is HREE enriched and LREE depleted with negative Eu-anomaly but without positive Ce-anomaly, and relatively flat patterns. The LA-ICP-MS U-Pb geochronology on the zircons yields a mean age of 133-0.87 Ma. Our data on zircon morphology, composition and U-Pb geochronology reveal that the parent magma of the quartz monzodiorite which was emplaced during late Yanshanian had a mixed crust-mantle source, with crustal components dominating. The magma is inferred to have been water rich and alkaline with initial high oxygen fugacity. Post-magmatic hydrothermal activity occurred under relatively reducing conditions which was conductive for gold precipitation in the Yixingzhai gold deposit.展开更多
文摘山西义兴寨金矿是五台山—恒山金矿集区内最为典型的金矿床,也是山西省最大的金矿床。近年来,在矿区河湾斑岩体的深部探矿过程中发现了一个大型蚀变斑岩型金矿体(>20 t Au)。然而,关于该蚀变斑岩金矿体的成因还缺乏相关的研究,因而制约了对该矿床深部及外围勘探工作的开展。本文通过对蚀变斑岩的锆石开展了LA–ICPMS原位的U–Pb同位素分析,结果表明蚀变石英斑岩的侵位时间为141±1 Ma,从而限定了蚀变斑岩金矿化的时间在131-141 Ma之间。对硫化物石英脉和蚀变斑岩型金矿石系统的元素地球化学分析结果表明两种类型矿石具有相似的特征,进而提出蚀变斑岩型金矿化与脉状金矿是同期成矿流体作用的结果。
基金supported by the Key Program of National Natural Science Foundation of China (Grand No.90914002)the China State Administrative Office of Ore-Prospecting Project for Critical Mines (Grant No.20089937)+1 种基金Nuclear energy research project:study on Sandstone-type uranium deposits prediction technology in Junggar superimposed large basin (Grant No.DH1142)the Introducing Talents of Discipline to Universities Program (B07011)
文摘The morphology, REE geochemistry and U-Pb geochronology of zircons from quartz monzodiorite in the Sunzhuang area, Fanshi County, Shanxi Province are presented in this study. The zircon crystals can be classified into four main types as： AB, L, S and P, and 24 subtypes such as AB4, ABs, Ls, and S3. The maximum crystallization temperature of zircon was estimated as 850℃, with the minimum of 550℃. The peak temperatures of the zircon crystallization range from 650℃ to 700℃. The abundances of Th and U in the zircon grains show large variation with the Th/U values 〉 0.4. The Th and U values also show a positive correlation in most zircons. The REE abundance of zircon in the quartz monzodiorite ranges from 280.4 ppm to 2143 ppm with an average of 856.4 ppm. The chondrite normalized zircon REE patterns show two types, one is characterized by HREE enrichment and LREE depletion with positive Ce-anomaly and negative Eu-anomaly whereas the other is HREE enriched and LREE depleted with negative Eu-anomaly but without positive Ce-anomaly, and relatively flat patterns. The LA-ICP-MS U-Pb geochronology on the zircons yields a mean age of 133-0.87 Ma. Our data on zircon morphology, composition and U-Pb geochronology reveal that the parent magma of the quartz monzodiorite which was emplaced during late Yanshanian had a mixed crust-mantle source, with crustal components dominating. The magma is inferred to have been water rich and alkaline with initial high oxygen fugacity. Post-magmatic hydrothermal activity occurred under relatively reducing conditions which was conductive for gold precipitation in the Yixingzhai gold deposit.
