Large-scale tectonic magmatism and extensive gold mineralization have occurred in the eastern North China Craton(NCC)(Jiaodong and Liaodong peninsulas)since Mesozoic,which indicated that the region experienced decrato...Large-scale tectonic magmatism and extensive gold mineralization have occurred in the eastern North China Craton(NCC)(Jiaodong and Liaodong peninsulas)since Mesozoic,which indicated that the region experienced decratonization process.The genesis type of granites evolved from S-type to I-type and A-type during Late Jurassic to Early Cretaceous,and thus reflects the evolution of geodynamics in the Late Mesozoic,indicating the varied subduction process of the Paleo-Pacific Plate(PPP)and the craton destruction.The evolution of geochemical features shows that the mantle beneath the Jiaodong Peninsula evolved from EM-II in Jurassic to EM-I in Early Cretaceous,demonstrating that the mantle switched from enriched to depleted.The gold of decratonic gold deposits in Jiaodong Peninsula mainly comes from the lithospheric mantle domains metasomatized by fluids derived from the metamorphism and dehydration of the subducted slab in the mantle transition zone.The rapid decomposition of minerals leads to the concentrated release of ore-forming fluids,and this process leads to the explosive gold mineralization during the craton destruction.Extensive magmatic uplift and extensional structures,triggered by the craton destruction in Early Cretaceous formed the extensional tectonic system,providing space for the decratonic gold deposits in Jiaodong Peninsula.展开更多
The recent deep prospecting results in the Jiaojia area of Eastern Shandong Province indicate that the Jiaojia ore field composed of several individual gold deposits as previously suggested is actually an ultra-large ...The recent deep prospecting results in the Jiaojia area of Eastern Shandong Province indicate that the Jiaojia ore field composed of several individual gold deposits as previously suggested is actually an ultra-large gold deposit.This deposit covers an area of ～40 km2,and shows a structural control by the Jiaojia fault and its secondary faults.Gold orebodies generally occur along the same mineralization-alteration belt,and the main orebodies intersect with each other or exhibit a parallel or overlapping distribution.This deposit＇s reserves are estimated to be 1,200t of gold,being the first gold deposit of more than 1000t gold reserves in China.The No.Ⅰ-1 orebody in the Shaling-deep Sizhuang ore blocks holds gold reserves greater than 350 t,or 29 percent of the total reserves,followed by the No.Ⅰ orebody in Matang-Jiaojia ore blocks with exceeding 150t gold reserves.This deposit mainly occurs in the footwall of the Jiaojia fault,and presents zoned patterns in mineralization,alteration and structures.The strongly mineralized zones agree with strongly altered and tectonically fractured zones.These orebodies display strataform-like,veinlike or lenticular shapes,and generally show characteristics of pinching out and reappearing,branching and converging,expanding and shrinking.The orebodies commonly occur along positions where the fault strike changes and in gentle locations with dips changing from steep to gentle.The main orebodies are parallel to the main plane of the orecontrolling fault,and tend to be gentle from the surface to the deep.The orebodies mainly plunge to the southwest,with plunge angle of 45°-606° Orebodies near the main plane of the ore-controlling fault have more gold resource than those away from main fault zone.The slant depth of orebodies is generally larger than the length along its strike direction; orebodies become thick and gold grades become low from the shallow area to the deep area.Ore-forming fluids are H2O-CO2-NaCl±CH4 type with medium-temperature and moderate to low salinity.Sulfur isotopic values （δ34SCDT） for gold ores range between 11.08‰ and 12.58‰,indicating mixed sulfur sources; hydrogen isotopic values （δDVSMOW） range from-83.68‰ to-116.95‰ and oxygen isotopic values （δ18OV-SMOW） range between 12.04‰ and 16.28‰.The hydrogen and oxygen isotopes suggest that ore-forming fluids originated from primary magma,and mixing with a large amount of atmospheric water during the late stage.The Eastern Shandong Province gold deposits are associated with magmatic activities which have mantle crust-mixed source,and also share some similarities with orgenic and epithermal hydrothermal golddeposits.Because Eastern Shandong Province gold deposits with unique metailogenic features and formation setting which are different from other gold deposit types in the world,we call it the Jiaojiatype gold deposits.The kiloton class Jiaojia gold deposit is related to fluid activities,extension and detachment resulted from thermal upweiling of magmas.The strong magmatic activities in the middle to late stage of early Cretaceous in Eastern Shandong Province lead to active fluids,and provided abundant ore-forming materials for gold depsoits.Moreover,many extensional structures resulting from crustal extension provided favourable space for orebody positioning.展开更多
基金Supported by projects of the Youth Science and Technology Innovation Fund of Shandong Provincial No.6 Exploration Institute of Geology and Mineral Resources(No.LY-QK-202203)National Natural Science Foundation of China-Shandong Joint Fund(No.U2006201).
文摘Large-scale tectonic magmatism and extensive gold mineralization have occurred in the eastern North China Craton(NCC)(Jiaodong and Liaodong peninsulas)since Mesozoic,which indicated that the region experienced decratonization process.The genesis type of granites evolved from S-type to I-type and A-type during Late Jurassic to Early Cretaceous,and thus reflects the evolution of geodynamics in the Late Mesozoic,indicating the varied subduction process of the Paleo-Pacific Plate(PPP)and the craton destruction.The evolution of geochemical features shows that the mantle beneath the Jiaodong Peninsula evolved from EM-II in Jurassic to EM-I in Early Cretaceous,demonstrating that the mantle switched from enriched to depleted.The gold of decratonic gold deposits in Jiaodong Peninsula mainly comes from the lithospheric mantle domains metasomatized by fluids derived from the metamorphism and dehydration of the subducted slab in the mantle transition zone.The rapid decomposition of minerals leads to the concentrated release of ore-forming fluids,and this process leads to the explosive gold mineralization during the craton destruction.Extensive magmatic uplift and extensional structures,triggered by the craton destruction in Early Cretaceous formed the extensional tectonic system,providing space for the decratonic gold deposits in Jiaodong Peninsula.
基金financially supported by the National Natural Science Foundation of China (Grant No. 41230311)the National Science and Technology Support Program (Grant No.2011BAB04B09)
文摘The recent deep prospecting results in the Jiaojia area of Eastern Shandong Province indicate that the Jiaojia ore field composed of several individual gold deposits as previously suggested is actually an ultra-large gold deposit.This deposit covers an area of ～40 km2,and shows a structural control by the Jiaojia fault and its secondary faults.Gold orebodies generally occur along the same mineralization-alteration belt,and the main orebodies intersect with each other or exhibit a parallel or overlapping distribution.This deposit＇s reserves are estimated to be 1,200t of gold,being the first gold deposit of more than 1000t gold reserves in China.The No.Ⅰ-1 orebody in the Shaling-deep Sizhuang ore blocks holds gold reserves greater than 350 t,or 29 percent of the total reserves,followed by the No.Ⅰ orebody in Matang-Jiaojia ore blocks with exceeding 150t gold reserves.This deposit mainly occurs in the footwall of the Jiaojia fault,and presents zoned patterns in mineralization,alteration and structures.The strongly mineralized zones agree with strongly altered and tectonically fractured zones.These orebodies display strataform-like,veinlike or lenticular shapes,and generally show characteristics of pinching out and reappearing,branching and converging,expanding and shrinking.The orebodies commonly occur along positions where the fault strike changes and in gentle locations with dips changing from steep to gentle.The main orebodies are parallel to the main plane of the orecontrolling fault,and tend to be gentle from the surface to the deep.The orebodies mainly plunge to the southwest,with plunge angle of 45°-606° Orebodies near the main plane of the ore-controlling fault have more gold resource than those away from main fault zone.The slant depth of orebodies is generally larger than the length along its strike direction; orebodies become thick and gold grades become low from the shallow area to the deep area.Ore-forming fluids are H2O-CO2-NaCl±CH4 type with medium-temperature and moderate to low salinity.Sulfur isotopic values （δ34SCDT） for gold ores range between 11.08‰ and 12.58‰,indicating mixed sulfur sources; hydrogen isotopic values （δDVSMOW） range from-83.68‰ to-116.95‰ and oxygen isotopic values （δ18OV-SMOW） range between 12.04‰ and 16.28‰.The hydrogen and oxygen isotopes suggest that ore-forming fluids originated from primary magma,and mixing with a large amount of atmospheric water during the late stage.The Eastern Shandong Province gold deposits are associated with magmatic activities which have mantle crust-mixed source,and also share some similarities with orgenic and epithermal hydrothermal golddeposits.Because Eastern Shandong Province gold deposits with unique metailogenic features and formation setting which are different from other gold deposit types in the world,we call it the Jiaojiatype gold deposits.The kiloton class Jiaojia gold deposit is related to fluid activities,extension and detachment resulted from thermal upweiling of magmas.The strong magmatic activities in the middle to late stage of early Cretaceous in Eastern Shandong Province lead to active fluids,and provided abundant ore-forming materials for gold depsoits.Moreover,many extensional structures resulting from crustal extension provided favourable space for orebody positioning.
