辽东五龙金矿田岩浆深部演化与金成矿作用：年代学及微区地球化学制约

Early Cretaceous intructive rocks and two types gold deposits, e.g., auriferous quartz vein type and altered rock type, develop in the Wulong gold district, eastern segment of the North China Craton. These gold deposits have close spatial relationship with intructive rocks. However, relationship between the magmatic evolution and gold mineralization, differents for mineralized mechanism of the two types of mineralization are rare studied in the Wulong district. The proposed project will focus on the relationship between gold mineralization and intructive rocks, and mineralized differents of the Wulong and Sidaogou deposits. LA-ICPMS U-Pb dating for zircon and pyrite Re-Os dating (or sericite 40Ar/39Ar dating) are used to provide constraints on the formation ages of gold ore-bodies and ore-related rocks. The association and distribution of trace elements in sulfide minerals, as well as compositions for individual melt inclusions will be analyzed by LA-ICPMS. In addition, in-situ sulfur istopic compositions of pyrites from different mineralization stages, the Wulong and Sidaogou deposits, will also be analyzed by SIMS or LA-MC-ICPMS. These geochronological and in-situ geochemical data will provide significant insights into the separation process of sulfide melt in the magma chamber and its contribution to the gold enrichment, as well as differents of mineralized mechanism of the auriferous quartz vein and altered rock types ore-bodies. Furthermore, the relationship between magmatic evolution process and gold mineralization, and mineralized differents, will be discussed to build a geologically reasonable metallogenic models for gold deposits in the Wulong district. Therefore, results of this proposal will significantly promote the understanding the relationship between large scale gold mineralization and destruction of the North China Craton.

华北克拉通东部的五龙金矿田内发育早白垩世侵入岩及与其具有密切关系的石英脉型和蚀变岩型金矿床。但深部岩浆演化过程与金成矿作用联系及矿化差异等方面研究薄弱。立项选取五龙和四道沟两个典型金矿床，在详细的野外地质调查和岩相学/矿相学观察基础上，综合利用锆石LA-ICPMS U-Pb、黄铁矿Re-Os或绢云母Ar-Ar定年法、硫化物熔融包裹体LA-ICPMS成分分析、硫化物LA-ICPMS微量元素及微区S同位素测试等先进测试技术，深入开展成岩成矿年代学、岩浆深部演化过程、熔体分离、金沉淀及矿化差异研究。从源区探讨岩浆活动对金成矿的贡献及矿化差异机制，建立合理的成矿模式，深化华北克拉通破坏与金大规模成矿作用这一科学问题的理解。

石英脉型和蚀变岩型金矿常常密切共生，但是两者的矿化差异机制及与深部岩浆演化之间的联系仍存在争议。华北克拉通东部的五龙金矿田内发育早白垩世侵入岩及与其具有密切关系的石英脉型和蚀变岩型金矿床，是研究这两种类型金成矿作用关联的理想对象。本项目以五龙石英脉型和四道沟蚀变岩型金矿床为重点研究对象，在详细的野外地质调查和岩相学/矿相学观察基础上，开展了年代学及矿物-全岩地球化学研究，取得主要结论及认识如下：（1）锆石U-Pb定年和前人的年代学成果厘定五龙金矿田的成岩与成矿时代均为126-119 Ma，金的成矿事件与早白垩世岩浆活动在时间和空间上具有强烈的耦合性。（2）五龙金矿田内大量发育的中基性脉岩群的成因研究表明，由于古太平洋板块的快速俯冲和回撤，辽东半岛岩石圈在早白垩世发生了大规模的减薄/破坏，伴随着深源的岩浆作用及金成矿事件。（3）五龙金矿田内大面积出露的早白垩世中酸性岩体具有壳幔混合的成因，进一步指示辽东半岛在早白垩世整体处于一个大规模的伸展构造背景。（4）野外地质调查、闪长质包体中硫化物熔融包裹体LA-ICPMS微区微量元素分析及常规/原位S-Pb同位素示踪表明，五龙金矿田的金成矿作用与三股流岩体关系不大，而与中基性脉岩所代表的深源壳幔混合岩浆相关。（5）综合矿床地质、流体包裹体、H-O同位素、硫化物LA-ICPMS微区微量元素及原位S同位素等研究，本文认为，五龙石英脉型和四道沟蚀变岩型金矿虽然存在矿化差异，但具有相似的成矿流体与成矿物质来源，且成矿时代相当，空间位置临近，应形成于同一深部岩浆系统。两者之间的矿化差异可能由赋矿围岩和控矿构造方面的差异导致。（6）建立了辽东五龙金矿田早白垩世深部岩浆作用与金成矿耦合模式，并提出五龙金矿田深部仍具有较大的成矿潜力，可为区域乃至同类型矿床找矿勘查工作提供借鉴与参考。在该项目的资助下，共发表论文10篇和国际学术会议论文2篇。