大兴安岭锂-铍-铌-钽等关键金属矿床类型、成矿规律与资源展望

Deposit types,metallogenesis and resource prospect of Li-Be-Nb-Ta deposits in the Great Xing an Range

大兴安岭地区是我国东部重要稀有金属成矿带之一,以发育大规模显生宙花岗岩和多期次叠合金属成矿作用为主要特征。稀有金属成矿作用主要发生在晚中生代,与高分异花岗岩密切相关。本文对大兴安岭地区锂铍铌钽矿床时空分布特征、成矿规律进行了系统总结,构筑了矿床成矿模型,指明了找矿方向,探讨了有待解决的若干重要科学问题。研究表明,大兴安岭锂铍铌钽矿床主要集中大兴安岭南段,锂、铌钽矿具有独立分布特点,而铍矿主要呈带状沿林西-甘珠尔庙断裂分布。矿化时代集中在150~130Ma之间,呈现出晚侏罗世铌钽矿化-早白垩世锂铍矿化的特征。锂铍铌钽矿床类型丰富,以花岗岩型为主,兼有火山岩型、碱性岩型、云英岩型和矽卡岩型矿化。本次研究认为大兴安岭地区具有良好的锂铍铌钽(锡钨)成矿潜力,不同矿化均与岩浆分异和后期热液交代作用相关,同时水-岩反应也会影响流体的组成和演化。岩浆流体出溶、地幔物质参与、流体溶蚀-再沉淀过程对锂铍铌钽成矿起到关键作用。未来重点勘查方向应关注与锡林郭勒杂岩体周边的高分异花岗岩有关的锂锡多金属,以及与大兴安岭火山岩和碱性岩有关的铍和铌钽矿化。

The Great Xing an Range(GXR)is one of the most important rare metal metallogenic belts in eastern China,which is characterized by large-scale Phanerozoic granites and multi-stage superposition metal mineralization.The rare metal mineralization in this belt is closely related to the highly fractionated granites,and mainly occurs in the Late Mesozoic.In this paper,the spatial-temporal distribution and metallogenies of Li-Be-Nb-Ta deposits in the GXR are systematically summarized,and by constructing an ore-forming model,the prospecting direction of these deposits is proposed.Moreover,some important scientific problems on the metallogenies of rare metals are discussed.This study showed that the Li-Be-Nb-Ta deposits in GXR are mainly concentrated in the southern part of GXR.Among them,the Li-Nb-Ta deposits have independent distribution characteristics,while the Be deposits are mainly distributed along the Linxi-Ganzhuermiao Fault.The metallogenic ages of these deposits are concentrated in 150~130Ma,showing the features of Late Jurassic Nb-Ta to the Early Cretaceous Li-Be mineralization.The Li-Be-Nb-Ta deposits in this region are mainly composed of granite-type,with some locally developed volcanic-,alkaline-,greisen-and skarn-types.We believe that there is a very high metallogenic potential for Li-Be-Nb-Ta-Sn-W in the GXR,and diverse mineralization is ascribed to the magmatic fractionation and late-stage hydrothermal metasomatism.Furthermore,water-rock reaction will also affect the composition and evolution of ore-forming fluids.Magmatic fluid exsolution,mantle material and fluid dissolution-reprecipitation process play a key role in the regional Li-Be-Nb-Ta mineralization.In the future,the key exploration direction should be focused on the Li-Sn polymetallic mineralization related to highly fractionated granites around the Xilingol complex,and the Be-Nb-Ta mineralization related to alkaline rock and volcanic rocks in the GXR.