铜陵地区岩浆演化与铜金成矿：单矿物原位元素和同位素研究

The genesis of magmatic rocks and ore deposits in Tongling region has been a subject of hot debate. Mesozoic dioritic intrusions have close genetic relationship with Cu-Au deposits, e.g., pyroxene diorite/pyroxene monzodiorite generally corresponds to gold deposits, quartz diorite/quartz monzodiorite related to copper deposits, and granodiorite is often associated with copper and polymetallic ore deposits. The connections behind is not clear, yet. The key to solve these problems is detailed constrained magma source region, oxygen fugacity, the source of ore-forming material, and magma evolution mechanism and copper-gold element enrichment. Based on whole rock geochemical studies, we plan to study representative copper and gold deposits and corresponding dioritic intrusive rocks from the Tongling region, using in situ trace element and isotope analyses for zircon from these dioritic rocks, and pyrite of different stages from typical mineralized alteration zone, aiming at better constraints on physical chemistry condition of different magma-fluid system magma, nature of end-member complements, and source of Cu and Au ore-forming materials, revealing deep and shallow geological process of magma-fluid system formation and evolution, illustrating activation, migration, distribution and enrichment regularity of copper and gold elements in magma and different mineralized stage, and constructing internal relationship of different magma evolution and copper, gold mineralization. The results may provide quantitative element-isotope geochemical indicators for deep ore prospecting and prediction of Tongling region, and new perspectives for dynamics mechanism of diagenesis and metallogenesis in eastern China.

铜陵地区岩浆岩和矿床成因存在较大争论，例如，闪长岩类与铜、金矿床有着非常有意义的成因耦合关系（辉石闪长岩一般对应于金矿床，石英闪长岩多对应铜矿床，花岗闪长岩常与铜、多金属矿床相对应），其原因至今悬而未解。解决这些问题的关键是对岩浆源区、氧逸度条件和成矿物质来源的详细制约，以及岩浆演化机制和铜金元素富集规律的厘定。在全岩地球化学研究的基础上，本项目选择本区典型铜、金矿床和相应的闪长岩体作为研究对象，开展闪长岩体中锆石、典型矿化蚀变带各阶段黄铁矿原位元素和同位素联合示踪研究，辨析不同岩浆-成矿流体系统物理化学条件、各端元组份的性质和铜、金等成矿物质来源，揭示岩浆-成矿流体系统形成与演化的深部与浅部过程，阐明铜、金元素在岩浆及各成矿阶段活化、迁移、分配和富集规律，构筑不同岩浆演化与铜、金成矿的耦合关系，为铜陵地区深部找矿与预测提供定量的地球化学制约，进而为中国东部成岩成矿动力学机制提供新的启迪。

安徽铜陵地区是中国东部重要的铜、金多金属产地之一，发育大量类型多样且典型的铜、金多金属矿床。这些铜、金多金属矿床时空上与晚中生代三类侵入岩（辉石二长闪长岩、石英二长闪长岩和花岗闪长岩）有密切的成因联系。本项目选择铜陵地区典型铜、金矿床和相应的三类侵入岩作为研究对象，应用多学科多技术方法，开展了三类侵入岩锆石年代学和Hf同位素、磷灰石原位地球化学、典型矿化蚀变带矿石矿物（如，黄铁矿）和蚀变矿物（如，石榴子石）原位地球化学以及流体包裹体研究，通过与相邻地区成岩成矿作用对比，取得了如下主要成果：（1）厘定了铜陵地区中生代三类成矿侵入岩精细年代学格架，明确了三类侵入岩的岩石类型、岩石系列、岩浆氧逸度和温度特征、岩浆演化过程和物质来源，建立了三类侵入岩的岩石成因和构造演化模式；（2）查明了铜陵地区层状硫化物矿床中黄铁矿的分布、共生关系、晶体形态等特征，厘定了黄铁矿中成矿元素赋存状态、微量元素的变化特征，明确了不同类型黄铁矿的成因，制约了层状硫化物矿床的成因；（3）查明了铜陵地区主要铜、金矿床的矿化蚀变、矿物组合、矿物世代及其晶体形态等特征，辨析了典型矿物中成矿元素赋存状态、微量元素的变化特征，总结了铜、金矿床成矿流体特征，制约了铜、金矿床成因；（4）完善了长江中下游成矿带中生代岩浆活动的精细年代学格架，厘定了安庆－贵池矿集区岩浆岩的岩石学、矿物学和元素－同位素地球化学特征，建立了该矿集区中生代构造－岩浆的动力学演化模型；（5）建立了皖南地区中生代两类花岗岩精细年代学格架，厘定了两类花岗岩的岩石类型、岩石序列和元素－同位素地球化学特征，建立了皖南地区两类花岗岩的岩石成因及其构造演化模式。本项目发表科研论文8篇，SCI收录论文5篇。项目成果构筑了岩浆演化与铜、金成矿的关系，丰富了铜陵及相邻地区基础地质资料，为中国东部成岩成矿作用研究提供新的启迪，为区域成矿规律和成矿潜力评价提供新的依据。