黔东南新元古代岩浆事件对Au-Cu多金属成矿的制约机理研究

The Zaibian-Daping district, Congjiang County,SE Guizhou Province,is characterized by Neoproterozoic magmatic activity frequently and Au-Ag-Cu-Pb-Zn-W-Sn polymetallic mineralization distribute widely. In this area, the age of Neoproterozoic igneous rocks have made much progress, but due to a lack of accurate ore-forming chronology researches and direct tracer methods for ore-forming metals, the sources of ore-forming metals, metallogenic age and relationship between Neoproterozoic magmatic activity and Au-Cu polymetallic deposits are still not clear. In this project, we are planning to take the typical Au-Cu polymetallic deposits (Nage, Dihu-Jiuxing) as example, based on the stematic field geological observations and detailed microscopic identification, the chalcopyrite Re-Os dating and systematic Cu isotopic compositions of chalcopyrite, igneous rocks (diabase, granite ) and hosting metamorphic rocks will be key analyzed,together with common geochemical data and previous research achievements, the source of the ore-forming metals, migration-precipitation process of the ore-forming elements, and the relationship between Neoproterozoic magmatic events and Au-Cu polymetallic mineralization will be revealed and found. Ultimately, more abundant information will be provided for constraining the tectonic property and metallogenic dynamics background of Jiangnan Block.

黔东南从江宰便-大坪一带新元古代岩浆活动频繁，Au-Ag-Cu-Pb-Zn-W-Sn多金属矿化广泛分布。该区域新元古代岩浆岩成岩时代的研究取得了诸多进展，但由于缺乏精准的成矿年代学数据和示踪成矿物质来源的直接手段，对区内Au-Cu多金属矿床成矿物质来源、成矿时代及与新元古代岩浆事件间的关系仍不清晰。本项目拟以区内具有代表性的Au-Cu多金属矿床（那哥、地虎-九星）为例，重点开展黄铜矿Re-Os同位素年代学研究和系统的黄铜矿、新元古代岩浆岩（基性辉绿岩、酸性花岗岩）和赋矿地层浅变质沉积岩（千枚岩和板岩）的Cu同位素地球化学研究。结合常规地球化学分析资料和前人研究成果，深入揭示Au-Cu多金属矿床成矿金属来源、精细刻画成矿元素迁移-沉淀过程、查明新元古代岩浆事件对Au-Cu多金属矿化的制约机理，为约束江南古陆大地构造属性和动力学背景提供更加丰富的信息。

江南造山带西南段的那哥、友能多金属是区内发现的中型铜矿床，矿体赋存于近EW向的断裂构造内，矿石类型为含铜石英脉型，首次发现辉砷钴矿主要以Co独立矿物形式产出。那哥Cu和原位S同位素指示成矿物质源自深部基性岩浆。宰便辉绿岩锆石U-Pb年龄表明岩浆侵位时代为新元古代早期。锆石Hf和主微量特征，揭示其原始岩浆可能源于富集地幔，并伴有一定的亏损地幔参与。新元古代早期宰便地区处于板内环境。黄铁矿原位微量元素种类少且含量偏低，指示其形成于低温的环境，相较而言，黄铁矿富集Co、Ni、Sb、As、Te、Cu、Pb、Zn等元素，其中Co、Ni、As和Se等元素以类质同象的方式赋存于黄铁矿之中，Te、Cu、Zn、Ag与Pb以包裹体的形式赋存于黄铁矿中。此外，黄铁矿的Co/Ni比值指示其为岩浆热液型黄铁矿。总体而言，那哥多金属矿床属于岩浆热液型中低温矿床。友能Pb-Zn矿床属构造控制热液矿床，Pb、Zn等金属元素来源与赋矿围岩关系密切。