华北克拉通北缘早白垩世金成矿与地幔物质的贡献

Contribution of mantle materials to Early Cretaceous gold mineralization in the northern margin of the North China Craton

华北克拉通北缘是我国重要的金成矿带,早白垩世金矿床主要分布在成矿带的中-东段赤峰-朝阳矿集区、五龙-猫岭矿集区、夹皮沟矿集区、老岭矿集区及附近区域。本文综述了华北北缘早白垩世金矿床的地质及同位素地球化学特征,讨论了早白垩世地幔组分参与金成矿的证据和过程。研究表明,华北北缘早白垩世金矿床与矿区内中-基性岩脉具有密切的时空关系;金矿脉中石英流体包裹体氢-氧同位素、碳酸盐矿物碳同位素及含金黄铁矿氦-氩同位素组成揭示成矿流体以岩浆水为主,具有壳-幔混合来源的特征;硫-铅-锶-钕同位素组成显示成矿物质具有显著的上地幔贡献。个别金矿床原位硫同位素组成反映成矿流体经历了强烈的水-岩反应,从围岩中萃取了部分硫等成矿组分。总体上,华北北缘早白垩世金矿具有基本一致的地质和地球化学特征,反映了幔源岩浆对金矿床的成矿流体及成矿物质具有重要贡献,其金成矿过程与早白垩世(140~120Ma)华北克拉通破坏及相关的壳幔相互作用有关。

Northern margin of the North China Craton(NCC)is an important gold metallogenic belt in China,the Early Cretaceous gold deposits are mainly distributed in the Chifeng-Chaoyang,Wulong-Maoling,Jiapigou and Laoling gold districts and nearby area.This paper discusses the evidence of the mantle components involved in the Early Cretaceous gold mineralization in the northern margin of NCC based on the geological and isotopic geochemistry characteristics.The Early Cretaceous gold deposits are closely related to the meso-mafic dikes in gold districts.Moreover,the hydrogen and oxygen isotopic composition of fluid inclusions in quartz,carbon isotope of carbonate minerals and helium and argon isotopes of pyrites reveal that ore-forming fluid is mainly magmatic water,which is characterized by crust-mantle mixing.The sulfur and lead isotopes of sulfides in the ores support a mixed crust-mantle source of the ore-forming materials,and the upper mantle contributes significantly to the ore-forming materials.Additionally,the in-situ sulfur isotopic composition of individual gold deposits shows that the magmatic-hydrothermal fluid haphazardly extracts ore-forming components from the host rock during the intense water-rock reaction.Generally,geological and geochemical characteristics of the Early Cretaceous gold deposits in the northern margin of NCC indicate that the mantle has significantly contributed to the ore-forming materials and fluids,which caused by the Early Cretaceous(140~120Ma)craton destruction and related crust-mantle interaction of the northern margin of NCC.