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    滇东南薄竹山矿集区晚白垩世岩浆活动及锡银铅锌钨多金属成矿作用

    The Late Cretaceous magmatism and Sn-Ag-Pb-Zn-W polymetallic mineralization in Bozhushan ore concentration area, southeast Yunnan

    • 摘要: 薄竹山锡银铅锌钨多金属矿集区位于华南褶皱系西缘,属于滇东南岩浆成矿带的重要组成部分。区内矿产资源丰富,以锡银锌钨矿床为主,兼有铅锌铁铜等多种金属矿产,矿床均围绕薄竹山岩体分布,其中以白牛厂超大型银多金属矿和官房大型钨矿最为典型。研究表明,薄竹山矿集区锡银铅锌钨多金属矿床的形成与晚白垩世岩浆活动存在密切的联系,其复式岩体成岩时代可以追溯至91.2~84.1 Ma,属晚白垩世岩浆活动的产物。晚白垩世酸性岩浆沿着薄竹山背斜核部与北西向断裂交合地带大规模侵位,在岩浆的顶托作用和底劈作用下,最终形成了薄竹山复式花岗岩体及白牛厂隐伏花岗岩体。薄竹山各单元岩体与白牛厂二长花岗岩、花岗斑体,以及团山、官房花岗岩均表现出一致的富硅(w(SiO2)为65.48%~74.92%)、富钾(w(K2O)为 4.17%~6.06%)的特征,岩石富集轻稀土元素(LREEs),具中等负铕异常,各岩体明显富集大离子亲石元素(LILEs),而相对亏损高场强元素(HFSEs),为一套准铝质—过铝质的钙碱性—高钾钙碱性S型花岗岩,形成于同碰撞造山及向碰撞后造山环境过渡的大地构造背景,属于造山运动的产物。区内成矿物质迁移与富集主要围绕着花岗岩体进行,发育形成了花岗岩接触带的夕卡岩型W、Sn、Fe矿床,碎屑岩–碳酸盐岩建造中的岩浆热液型Ag、Pb–Zn、Sn、Cu及外围地层中低温热液型Sb矿,这在区域上构成较为完整的与花岗岩侵位有关的岩浆热液成矿系统。

       

      Abstract: The tin-silver-lead-zinc-tungsten polymetallic ore concentration area of Bozhushan is located at the western edge of the South China Fold System and is an important part of the magmatic-mining belt in southeast Yunnan. The mineral resources in the area are rich, mainly tin-silver-zinc-tungsten deposits, and some other metal minerals (e.g. lead-zinc-iron-copper minerals). All the deposits are distributed around the Bozhushan rock body, among which the Bainiuchang ultra-large silver-polymetallic mine and the Guanfang large tungsten mine are the most typical. Studies have shown that the formation of the tin-silver-lead-zinc-tungsten deposits in the Bozhushan ore district is closely related to the Late Cretaceous magmatism, with the complex rock formations dating back to 91.2 to 84.1 Ma ago, and are the product of Late Cretaceous magmatism. The Late Cretaceous acidic magma was massively intruded along the intersection of the core of the Bozhushan anticline and the north-west trending fracture zone, and eventually led to the formation of the Bozhushan complex granite body and the Bainiuchang concealed granite body under the top-supporting and bottom-splitting action of the magma. The granite bodies of the Bozhushan unit show consistent geochemical characteristics with the Bainiuchang monzonitic granite and granite porphyry, as well as the Tuanshan and Guanfang granites, which are silica-rich (SiO2 content of 65.48%~74.92%) and potassium-rich (K2O content of 4.17%~6.06%). The rocks are enriched in light rare earth elements (LREEs), clearly enriched in large ion lithophile elements (LILEs), and relatively deficient in high field strength elements (HFSEs), with moderate negative europium anomalies. They belong to calcium alkaline to high potassium calcium alkaline quasi-aluminous to peraluminous S-type granites which formed in a geotectonic context of synclinal orogeny and transition to a post-collisional orogenic environment, being the result of orogeny. The migration and enrichment of mineralised material in the area mainly revolves around the granite bodies, led to the formation of siliciclastic W, Sn, and Fe deposits in the granite contact zone, magmatic hydrothermal Ag, Pb-Zn, Sn, and Cu in the clastic-carbonate construction and low-temperature hydrothermal Sb ores in the peripheral strata, which constitute a relatively complete magmatic hydrothermal mineralization system related to granite intrusion in the region.

       

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