湘东邓阜仙地区白云母花岗岩与W-Sn成矿的关系：微区地球化学和同位素制约

Recent studies concluded that between 160 and 150 Ma (Late Jurassic) was the time of major W–Sn mineralization in Nanling Range, South China. However, more and more studies of W–Sn mineralization during 145–130 Ma is reported, and researchers proposed the W–Sn mineralization is likely related to the muscovite granite. The Dengfuxian intrusive complex located at the middle section of the Nanling Range tungsten-tin metallogenic belt, comprising biotite granite, two-mica granite and muscovite granite. The Xiangdong W-Sn deposit occurred in the intrusive complex was considered to associate with the Late Jurassic magmatism. However, project candidates observed cassiterite-wolframite-quartz veins and widespread cassiterite grains occurred in the muscovite granite (Whole rock K-Ar ages: 136–110 Ma). In order to constrain the formation age and genesis of the muscovite granite and W-Sn mineralization in the Dengfuxian district, and to better understand the genesis link, this project chooses muscovite granite and W-Sn mineralization quartz-veins in the Dengfuxian district as the investigation subject. Petrography, mineral chemistry, elementary and isotopic geochemistry, as well as zircon and cassiterite U-Pb dating and trace elements analysis, will be carried on muscovite granite and W-Sn mineralization quartz-vein. By comparing with previous data obtained during the early Cretaceous in the adjacent area (e.g. North Jiangxi district, Middle-Lower Yangtze River Valley Metallogenic Belt and Southeastern Coastal Metallogenic Belt), we aim to guide for explorations and better understand the magmatic-hydrothermal mineralization events and geodynamic setting during the Cretaceous in South China.

南岭地区钨锡多金属成矿作用与区内广泛分布的复式花岗岩体有关。前人研究表明成矿时限主要集中于晚侏罗世，但近年来早白垩世(145~130Ma)钨锡成矿作用也陆续被一些学者报道，并认为可能与白云母花岗岩有关。邓阜仙复式岩体（黑云母花岗岩-二云母花岗岩-白云母花岗岩）位于南岭中段，其中产出的湘东钨锡矿床与晚侏罗世二云母花岗岩密切相关。然而申请人在区内白云母花岗岩(前人K-Ar年龄136~110Ma)中也发现有含锡石黑钨矿石英细脉，且矿化脉周围的花岗岩中广泛发育锡石，表明白云母花岗岩与钨锡成矿有关。故本项目拟选择白云母花岗岩及矿化石英脉为研究对象，开展全岩地球化学、锆石和锡石的原位U-Pb定年以及微量元素等分析，精确厘定本区白云母花岗岩和矿化石英脉的形成时代，查明两者的形成机制及其相互关系，为华南钨锡找矿提供新思路。并通过邻区对比研究，深入理解华南白垩纪岩浆热液成矿事件及地球动力学机制。

邓阜仙复式岩体位于南岭中段，其中产出的湘东钨锡矿床与晚侏罗世二云母花岗岩密切相关。申请人在区内白云母花岗岩中新发现有含锡石黑钨矿石英细脉，且矿化脉周围的白云母花岗岩中广泛发育锡石，表明白云母花岗岩与钨锡成矿有关。该白云母花岗岩侵位于黑云母花岗岩和二云母花岗岩，但该白云母花岗岩和其中产出的含钨锡石英脉的形成时代不清，两者成因联系不明。鉴于此，本项目重点开展了白云母花岗岩和其中产出的含钨锡石英脉的形成时代和成因机制研究。白云母花岗岩中锆石的U-Pb年龄为145~142 Ma，而对白云母花岗岩中含钨锡石英脉以及湘东钨锡矿床中的锡石进行定年，得到两组U-Pb年龄，分别为152 Ma和141~137 Ma。白云母花岗岩的全岩Sr-Nd同位素联合锆石Hf同位素结果指示邓阜仙地区白云母花岗岩与该区不同期次各岩相花岗岩具有近似同源的特征，均源于中元古代地壳物质，而邓阜仙复式岩体可能为同一源区（中元古代地壳物质重熔）岩浆阶段性结晶分异所形成。综合研究可知，邓阜仙地区存在两期钨锡成矿叠加，第一期为晚侏罗世，成矿与晚侏罗世二云母花岗岩有关；第二期为早白垩世，成矿与早白垩世白云母花岗岩有关。本项目研究成果指出，早白垩世是华南地区新识别出的重要钨锡成矿期，而白云母花岗岩是华南钨锡找矿新的勘查目标。

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