胶东邓格庄金矿床成因:地质年代学和同位素体系制约

邓格庄金矿地处华北克拉通胶东半岛东部苏鲁超高压带内,黄金储量已超过50t,是胶东牟平-乳山成矿带第二大石英脉型金矿床。矿体产于昆嵛山岩体和荆山群变质岩接触带附近的昆嵛山岩体中,金矿体受控于金牛山断裂带西侧的次级断裂。矿石中的硫-铅-氢-氧同位素值表明成矿流体主要来源于岩浆,具有以地壳为主兼具地幔混合特征,通过深渊断裂发生迁移,在成矿晚期遭受天水混染。围岩昆嵛山二长花岗岩高精度的锆石U-Pb年龄为155. 8Ma,成矿前期蚀变岩中蚀变矿物钾长石和绢云母~(40)Ar-~(39)Ar精确测年结果分别为123Ma和104Ma。结合近年来前人的研究资料,我们建立了胶东金矿集区中生代岩浆岩演化序列,将其划分为160～150Ma、130～110Ma、110～100Ma三个阶段,并给出了大规模爆发式成矿的年龄峰值(120±10Ma)。认为邓格庄金矿既非以变质流体为特征的典型造山型金矿,也非浅成低温热液型金矿,而是伴随华北克拉通岩石圈减薄、软流圈物质上涌、地壳拉张而使壳幔混合流体在浅部以大纵深脉状集中成矿为基本特征的中温岩浆热液型金矿。

The genesis of Denggezhuang gold deposit in Jiaodong: Constraints from multigeological chronology and isotope system

The Dunggezhuang gold deposit is located in the Sulu ultrahigh pressure (UHP) metamorphic belt in the eastern Jiaodong Peninsula, North China Craton. Its gold reserves have exceeded 50t so far explored. It is the second largest quartz vein type gold deposit in the Mouping-Rushan metallogenic belt, Jiaodong. The orebody occurs in the Kunyushan rock mass near the contact zone between the Kunyushan monzogranite and the Jingshan Group metamorphic rock, and the gold orebody is controlled by the secondary faults on the west side of the Jinniushan fault zone. The S-Pb-H-O isotopic compositions indicate that the ore-forming fluids are mainly derived from magmatic sources and have crustal and mantle mixing characteristics. They migrated through deep faults and are contaminated by meteoric water in the late stage of mineralization. The Kunyushan monzogranite was emplaced at 155.8Ma. The accurate dating results of the altered minerals K-feldspar and sericite ⁴⁰Ar-³⁹Ar in the pre-metallogenic altered rocks are 123Ma and 104Ma, respectively. Combined with previous data, the Mesozoic magmatic rock evolution sequence in this region is established, which can be divided into 160~150Ma, 130~110Ma and 110~100Ma stages, with the peak age value of large-scale explosive mineralization around 120±10Ma. It is considered that the Denggezhuang gold deposit is neither a typical orogenic gold deposit characterized by metamorphic fluids nor an epithermal gold deposit, but a medium-low temerature magmatic hydrothermal gold deposit characterized by large-depth vein-like concentration in shallow crust and mantle mixed fluids accompanied by lithospheric thinning, asthenospheric material upwelling and crustal extension in the North China Craton.