峨眉山大火成岩省烂纸厂铁矿床地质特征、成因及其找矿勘查启示

烂纸厂铁矿床是峨眉山大火成岩省玄武岩建造中查明的首例中型规模铁矿床。矿床的形成与玄武岩建造具有密切的时空及成因联系,矿体主要赋存于峨眉山玄武岩下段致密块状玄武岩与玄武质角砾岩接触带附近,产出特征受矿山梁子破火山口构造控制,多层位产出,矿石发育草莓状结构、韵律结构和纹层状构造、条带状构造、致密块状构造、绳状构造、角砾状构造等矿石组构,发育铁质结核和铁碧玉,同生沉积层控成矿特征明显。岩(矿)石主、微量元素分析结果表明,研究区岩浆演化遵循Fenner分异趋势,成矿作用与热水沉积作用有关。地质和地球化学特征表明,矿床成因类型为火山喷发(溢)沉积型陆相火山岩型铁矿床。烂纸厂铁矿床是我国在铁矿找矿勘探类型上的新突破和在峨眉山大火成岩省找矿实践取得的新进展,它的发现打破了在玄武岩建造中不具备寻找成型矿床的固有勘查模式的思想束缚,为相似地质环境寻找铁矿给予了诸多启迪和经验借鉴。

Geological Characteristics,Genesis,and Its Prospecting Exploration Enlightenment of Lanzhichang Iron Deposits in the Emeishan Large Igneous Province

Lanzhichang iron deposit is the first medium‐scaled iron deposit ascertained in a basalt construction of the Emeishan large igneous province . The deposit has a close spatial‐temporal and genesis relationship with the basalt construction that is significantly of synsedimentary stratabound mineralization characteristics .The orebodies mainly occurred in the contact zone between the basaltic breccia basalt and the compact massive basalt of the lower section of Emeishan basalt controlled by Kuangshanliangzi caldera structure with multi‐layers ,and the ores developed fabric structure such as straw berry‐like structure ,rhythmic and laminar structures ,banded structure ,dense massive structure , rope structures ,brecciated structure and so on ,as well as iron tuberculosis and iron jasper .The major and trace elements of rock and ore show that the mineralization was affected by the hydrothermal sedimentary , magmatic evolution following the Fenner differentiation trend . The geological and geochemical characteristics indicate that Lanzhichang iron deposit is a continental syndepositional iron ore deposit with volcanic eruption or overflow . The discovery of this new type of iron deposit is a breakthrough to the ideological restraint in China that no such scaled iron deposit can be found in an igneous area .It provides a lot of inspirations and references for looking for iron ore in similar geological environments .