河南三门峡贯沟铝土矿矿物组成及其特征

摘 要] 河南三门峡市贯沟铝土矿属喀斯特型铝土矿。研究区内地层发育相对完全,除上奥陶统、 志留系、泥盆系和下石炭统地层缺失外,从太古界到新生界均有出露。铝土矿层主要产出于中石炭系本 溪组下段。矿石以鲕粒和隐晶质结构为主,少量碎屑结构。矿物学分析显示,铝土矿矿石的主要组成矿 物有硬水铝石、锐钛矿、伊利石,另外,还包括少部分高岭石、锆石等。硬水铝石呈隐晶质结构组成矿石 的基质,少部分呈现细小的板状、长柱状形态。锐钛矿存在两种形态:第一种是锐钛矿与硬水铝石二者 同期形成;第二种锐钛矿以脉状穿插在硬水铝石组成的基质中,形成稍晚于硬水铝石。伊利石主要呈鳞 片状集合体形态组成矿石的基质。锆石主要分散在硬水铝石组成的基质中。进一步研究发现:硬水铝 石电子探针分析显示晶体中存在Fe、Si 和Ti 等其它元素,其主体呈隐晶质与锐钛矿密切共生,指示硬水 铝石主要为简单的成岩结晶成因。矿石中的锐钛矿和硬水铝石共生,互相包含和穿插,反映大量的锐钛 矿是成矿期或成岩期结晶形成。对风化作用中形成的伊利石主要由云母转化而形成,该过程中矿物结 构并未发生明显改变。

Mineral Composition and Characteristics of the Guangou Bauxite Deposit in Sanmenxia City, Henan Province

Abstract:The Guangou bauxite deposit in Sanmenxia City, Henan Province is of karst type. Except the Ordovcian, Silurian, Devonian and Lower Carboniferous Strata, all the other Archean to Cenozoic strata outcrop in this region. The Guangou bauxite horizon occurs in the middle Carboniferous Benxi Formation. The ores are dominated by oolite and aphanitic textures, with a few clastic textures. Mineralogical analysis reveals that the main minerals in bauxite ores are diaspore, anatase and illite, with a little kaolinite and zircon. Diaspore is the base of ores in aphanitic texture, with some thin tabular and long bar textures. Anatase developed in two shapes, one paragenesis with diaspores, and the other developed as veins in the diaspores bases. Illites mainly developed as aggregations which also make up the base of ores, and zircon mainly dispersed in the bases. It is also found Fe, Si and Ti elements in diaspore by EPMA analysis. Diaspore mainly coexists with octahedrites, which shows diaspore is mainly simple diagenesis minerals. The coexistence of diaspore and anatase also illuminates that octahedrites were formed in the mineralization or diagenesis stage. Illite was mainly formed by mica in weathering stage, and no obvious alterations of mineral textures happened in this process.