澜沧江铁矿带惠民式-疆峰式铁矿床特征与含铁建造

Mineralization features and iron formation of Huimin-and Jiangfeng-style ore deposits in Lancangjiang iron ore belt

通过对惠民式和疆峰式铁矿的研究,认为它们都是受变质中基性火山岩建造控制的海相火山-沉积型铁矿床,前者兼有条带状含铁建造(BIF)和粒状含铁建造(GIF)的特征,而后者则为条带状含铁建造。它们均具备元古代条带状铁硅建造铁矿的特征,满足形成前寒武纪大型条带状含铁建造的"大型海洋热液供应系统、作为沉积仓储的大陆架体貌及有能力联系这两者的海洋层体"三要素,以及形成大型火山-喷流-沉积型铁矿的条件。赋存惠民式和疆峰式铁矿的元古代澜沧岩群及大勐龙岩群构成了澜沧江铁矿成矿带,其同生喷流沉积-内生蚀变改造-外生淋滤富集的演化特点清楚。澜沧岩群中的惠民式铁矿属火山-沉积苏必利尔湖型铁矿,与锰共生;大勐龙岩群中的疆峰式铁矿为火山-喷流阿尔果马型铁矿,以含少量硫为特征。这两类铁矿床从火山喷流沉积到变质改造等,均可在矿床成因模式中找到相应的位置。研究结果表明,在该区寻找条带状含铁建造铁矿的潜力巨大。

A study of the Huimin-and Jiangfeng-style iron deposits has revealed that the marine volcanogene sedimentary type Huimin and Jiangfeng ore deposits are controlled by metamorphosed intermediate-basic volcanic formation.The former（Huimin-style） consists of both banded iron formation（BIF） and granular iron formation（GIF） whereas the latter（Jiangfeng-style）,consists only of banded iron formations（BIF）.The possess of the formation of Proterozoic bended siliceous iron formation possesses the features of ＂a large-scale supply of aqueous iron from the oceanic hydrothermal system;the existence of large continental shelves to serve as deposition repositories and a stratified ocean capable of connecting the two＂,thus satisfying the three essential factors for forming large-size volcanogene-exhalative-sedimentary type iron deposits.The Lancangjiang iron ore belt is composed of Huimin-and Jiangfeng-style ore deposits hosted by strata of Proterozoic Huimin Group and Damenglong Group,and the evolutional characteristics of syngenetic exhalative sedimentary-hypogene alteration-supergene leaching and enrichment are obvious.The Huimin-style iron ore deposits of Huimin Formation in the Lancang Group belong to the volcano-sedimentary Superior Lake type,in association with manganese,whereas the Jiangfeng-style iron ore deposits of Damenglong Group may be regarded as the volcano-exhalative Algoma type characterized by the existence of minor sulfur.On the whole,for the mineralization from volcano-exhalative sedimentation to metamorphism and transformation we can find the relevant parts from the ore deposit metallogenic model,and hence the model offers a great potential in search for bended iron formation in this region.