重庆南川-武隆铝土矿矿物学、地球化学特征

重庆南川-武隆铝土矿属于渝南-黔北铝土矿成矿带,为喀斯特型铝土矿床。经显微镜、X射线粉晶衍射、矿物自动分析仪（MLA）、扫面电子显微镜等方法对该矿床矿物学的研究,发现组成铝土矿的主要矿物为一水硬铝石、高岭石、绿泥石,次要矿物为伊利石、一水软铝石、三水铝石、鲕绿泥石、菱铁矿、赤铁矿、针铁矿、黄铁矿、锐钛矿、金红石、磷灰石、石英、锆石、方解石、长石及稀土矿物等。矿石组构及矿物组合表明形成铝土矿的沉积/成岩环境为接近于潜流的环境。矿石结构和锆石形态指示成矿物质经过了短距离的搬运。地球化学研究结果显示,组成铝土矿的主要化学成分为Al2O3、TFeO、SiO2和TiO2,铝土矿化过程中REE、Zr、Hf、Nb、Ta、Th、Sc、Li和Ga发生富集。形成铝土矿的母岩物质主要来自下伏页岩的风化作用,灰岩和酸性火山岩对铝土矿的形成也有一定的贡献。结合稳定同位素资料,认为铝土矿的形成可能与生物作用有关。

Mineralogical and geochemical characteristics of the Nanchuan-Wulong bauxite deposit in Chongqing

The Nanchuan-Wulong bauxite deposit in Chongqing are ascribed to the karst bauxite deposit hosted in southern Chongqing-northern Guizhou bauxite belt. The mineralogical analysis on the basis of microscopic examination, X-ray power diffraction patterns, MAL and SEM-EDS has revealed that diaspore, kaolinite and chlorite are the major minerals in the bauxite ores with the minor minerals such as illite, boehmite, gibbsite, chamosite, siderite, hematite, goethite, pyrite, anatase, rntile, apatite, quartz zircon, calcite, feldspar and small amounts of rare-earth minerals. The ore fabrics and mineral assemblages indicate that the Nanchuan-Wulong bauxite deposit were formed in the depositional-diagenetic environments close to the phreatic zone. Both the ore textures and morphology of zircon grains also indicate that much of bauxitic soils were once transported in a short distance. Geochemically, the major chemical compositions in the bauxite ores consist of A1203, TFeO, SiO2 and TiO2. The elements REE, Zr, Hf, Nb, Ta, Th, Sc, Li and Ga are enriched as well in the bauxitization processes. The underlying shale, carbonate rocks and acidic volcanic rocks are believed to contribute the mother materials to the formation of the bauxite deposits. In addition, the formation of the bauxite deposits may have something to do with microorganisms.