铁氧化物矿床与铜金矿床之间的关系--以宁芜盆地中玢岩铁矿和铜金矿为例

The relationship between iron oxide deposits and Cu-Au deposits is an important issue in the modern economic geology, and its research is in full swing in the world. On the basis of previous work of the Ningwu basin, the Fund focuses on geology and geochemistry of the Meishan and Tongjing copper-gold deposits, age and tectonic setting of the Niangniangshan cycle volcanic-subvolcanic rocks and intrusions. Based on wall rock alteration, fluid inclusion, isotope and age of the Meishan and Tongjing copper-gold deposits, the Fund discusses source and evolution of the ore-forming fluid and material, and relationship between the Cu-Au deposits and volcanic-subvolcanic rocks. The copper-gold mineralization, and its mechanism and tectonic background will be presented in order to establish a copper-gold metallogenic model in the Ningwu basin in the Fund. On the basis of previous work of the porphyry iron deposits, combined with the copper-gold mineralization, and its mechanism and tectonic background in the Ningwu basin, the relationship between the iron oxide deposits and Cu-Au deposits will be discussed with an aim of establishment of a regional scale Fe-Cu-Au copper-gold metallogenic model. The Fund will not only promote a research of the volcanic-type iron copper-gold deposit in China with the international research standards, provide a new entry point to discuss relationship between the Kiruna iron deposit and associated Cu-Au deposit, but also drive the prospecting and explanation of the Ningwu Basin or even Mesozoic volcanic basin in eastern China.

铁氧化物矿床与铜金矿之间的关系是当今矿床学研究的前沿，国际上对其研究正在如火如荼进行。在前人工作的基础上，本基金重点解剖梅山和铜井铜金矿床，研究娘娘山组火山-次火山岩及侵入体的成岩时代及形成的构造背景；通过岩石地球化学、围岩蚀变、流体包裹体、同位素和成岩成矿年代学研究，查明梅山金铜矿和铜井铜金矿床的成矿物质和成矿流体来源及演化，探讨火山-次火山岩与铜金矿床之间的关系；研究宁芜盆地中铜金矿类型、成矿机制及形成的构造背景，建立铜金矿床成矿模型; 在前人玢岩铁矿研究的基础上，结合本项目铜金矿类型、形成机制和成矿背景的系统研究，探讨铜金矿与玢岩铁矿之间的关系，建立区域铁铜金成矿模型。本项目将会推进我国火山岩型铁铜金矿床研究与国际前沿研究接轨，为探讨基鲁纳型铁矿与铜金矿（包括IOCG矿床）之间的关系这一重大的课题提供新的切入点，同时会推动宁芜盆地甚至我国东部中生代火山盆地找矿勘查。

铁氧化物矿床与铜金矿床之间的关系研究是当今矿床学研究的前沿领域。宁芜地区铜金矿的寻找多年来未获突破，需要很好地论证铜金矿与玢岩铁矿之间的关系，这一关系长期被忽视。主要研究内容包括：梅山金-铜矿和铜井矿床铜-金矿床典型矿床解剖；娘娘山组火山-次火山岩的源区及形成的动力学背景；宁芜盆地中铜金矿与玢岩铁矿之间的内在联系；宁芜盆地中铁铜金矿床组合与IOCG矿床之间的异同点。梅山成矿母岩辉长闪长玢岩LA−MC−ICP−MS 锆石U−Pb年龄为138.0～141Ma，LA− ICP−MS 榍石U−Pb谐和年龄为134 Ma，自阶段Ⅱ（类矽卡岩阶段）→阶段Ⅲ（赤铁矿和菱铁矿化）→阶段Ⅳ（石英−硫化物阶段），成矿流体温度和盐度有逐渐下降趋势。阶段Ⅰ、Ⅱ和Ⅲ成矿流体主要为岩浆流体，成矿流体在阶段Ⅳ与大气降水混和时，加速了硫化物沉淀，产生了相应的金矿化。铁氧化物矿床（玢岩铁矿）和铜-金矿床形成于同一岩浆-热液成矿系统，与辉长闪长玢岩具密切时空成因上联系。铜井娘娘山组火山岩LA−MC−ICP−MS 锆石U−Pb年龄约130 Ma，石英-绢云母化蚀变带中绢云母坪年龄为131Ma。铜井铜-金矿床硫化物位于0.4 ~4.7‰之间，平均值为3‰，反映硫单一来源，最可能为岩浆硫。阶段Ⅰ成矿流体起源于早期岩浆流体与大气降水经历了交换反应。铜井铜-金矿床是个火山-次火山热液矿床，矿床的形成与娘娘山组火山-次火山岩具有密切的成因联系。娘娘山组火山岩火山岩源区应为起源于受到古太平洋板块俯冲作用沉积物影响的富集地幔源区。宁芜盆地中铁铜金矿床组合受控于岩石圈变薄、软流圈上涌的环境，形成于陆内张性构造背景。宁芜盆地中铁铜金矿床组合与基鲁纳型铁矿床和IOCG矿床存在相似性。本基金研究成果大大推动了宁芜盆地中铁铜金矿床研究与国际前沿研究相接轨，将会有力地推动相似背景火山岩盆地铁铜金矿床的找矿勘查，实现找矿的新突破。