Genesis of tin-dominant polymetallic deposits in the Dachang district, South China: Insights from cassiterite U-Pb ages and trace element compositions
Genesis of tin-dominant polymetallic deposits in the Dachang district, South China: Insights from cassiterite U-Pb ages and trace element compositions
复制标题
华南大厂地区以锡为主的多金属矿床成因：来自锡石U-Pb年龄和微量元素组成的见解
DOI：
10.1016/j.oregeorev.2018.03.023
复制
发表时间：
2018
影响因子：
3.3
通讯作者：
Zhang Lichuan
中科院分区：
文献类型：
--
作者：
Guo Jia;Zhang Rongqing;Sun Weidong;Ling Mingxing;Hu Yongbin;Wu Kai;Luo Ming;Zhang Lichuan
大厂锡多金属矿区位于中国南方西部，总储量1.1亿吨，锡含量1%，副产品锌、铅、锑、铟、铜含量3 - 5%，银含量100 - 300克/吨。区内锡矿经济矿体主要产于泥盆系灰岩、黑色页岩和硅质岩中，呈块状/层状和脉状/网脉状矿化。对采自铜坑-长坡、高峰锡锌铅矿床、大福楼、会乐、康马锡锌矿床的7个铅辉石样品进行了LA-ICP-MS U-Pb定年，得到Pb-206/U-238加权平均年龄为90.3 ± 1.8Ma~95.4 ± 4.9Ma。这些年龄明显比泥盆纪含矿地层年轻，但在分析不确定性范围内，与先前发表的龙香盖黑云母花岗岩锆石U-Pb年龄（96.6 - 93.9Ma）吻合较好，表明花岗岩岩浆活动与锡矿化之间存在密切的时间联系。大厂地区不同矿石类型的锡石颗粒阴极发光图像显示出明显的生长分带。LA-ICP-MS微量元素分析结果表明，铁白云石中Ti、Fe、W含量较高，Nb、Ta含量较低，与其发光特征相一致。不同矿石类型（硫铁矿-硫化物矿石和含硫铁矿的石英脉）中硫铁矿的化学成分差异不大，但硫铁矿-石英脉中硫铁矿中的铁更富集。结合白垩纪U-Pb年龄，锡石中Fe、W含量的升高表明大厂地区以锡为主的多金属矿床形成于受龙祥盖黑云母花岗岩控制的与花岗岩有关的岩浆热液体系中，排除了同生成因。
The Dachang tin-dominant polymetallic district in western South China, hosts a total reserve of 110 Mt ore @ 1% Sn, 3-5% by-products of Zn, Pb, Sb, In and Cu, and 100 to 300 g/t Ag. Economic tin orebodies in the district mainly developed in Devonian limestone, black shale and siliceous rocks, as massive/stratiform and vein/ stockwork mineralization. LA-ICP-MS U-Pb dating on seven cassiterite samples from the Tongkeng-Changpo and Gaofeng Sn-Zn-Pb deposits, and the Dafulou, Huile and Kangma Sn-Zn deposits, yields weighted mean Pb-206/U-238 ages ranging from 90.3 +/- 1.8Ma to95.4 +/- 4.9 Ma. These dates are significantly younger than the Devonian ore-hosted strata, but agree well with the previously published zircon U-Pb ages of 96.6-93.9 Ma for the Longxianggai biotite granite within analytical uncertainties, showing a close temporal link between the granitic magmatism and tin mineralization. Cassiterite grains from various ore types in the Dachang district show clear growth zonations as reflected from their cathodoluminescence images. LA-ICP-MS trace element analyses of cassiterite grains indicate that they have relatively high Ti, Fe and W but low Nb and Ta contents, which corresponds to the clear luminescencing. Chemical variations of cassiterite from different ore types, i.e. cassiterite-sulfide ores and cassiterite-bearing quartz veins, are indistinguishable, except for more enriched Fe in cassiterite from cassiterite-quartz veins. Combined with Cretaceous U-Pb ages, elevated Fe and W contents of cassiterite suggest tin-dominant polymetallic deposits in the Dachang district were formed in a granite-related magmatic-hydrothermal system controlled by the Longxianggai biotite granite, precluding their syngenetic origin.