【作者】 陈阳；

【导师】 尹福光；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2012， 硕士

【摘要】 在铝土矿整装勘查项目进行过程中,为了给铝土矿找矿提供基础性地质研究资料,同时为渝南铝土矿成因提供依据,论文选取大佛岩铝土矿为典型矿区,进行了区域沉积背景分析,选择典型剖面精细研究,同时采集岩石镜下鉴定薄片、主微量测试、微体古生物鉴定、电子探针及能谱分析样品,在综合分析的基础上,建立沉积微相划分及组合标准；通过编制矿区含矿岩系岩相古地理图,以对沉积微相展布和岩相古地理概貌进行研究；通过平面上Al2O3含量等值线图和岩相古地理图对比,以及纵向上典型剖面和Al2O3含量变化对比,探讨铝土矿成矿的有利沉积相带。区域构造演化史显示,受广西运动影响,扬子板块大部分地区上升为陆,遭受从中志留世到中二叠世早期的风化剥蚀,随后,水平面上升,在合适的气候条件下,形成了渝南铝土矿。区域沉积背景分析发现,区域上铝土矿赋存的梁山组存在3种不同的剖面结构,北部为代表渴湖沉积环境的含铝岩系,大佛岩铝土矿位丁在该渴湖北部边缘；中部和北东部为障壁沙坝环境沉积的高成熟度石英砂岩；南部为正常浅海沉积。含矿岩系典型剖面岩性分析表明含矿岩系有河流、滨湖、浅湖和深湖沉积形成的结构构造,剖面上从下到上为连续的水体深浅变化过程；孢粉结果反映当时气候为温暖潮湿,沉积水体为淡水；微量元素地球化学分析显示渝南铝土矿含矿岩系的沉积环境为总体以淡水为主,在海平面升降过程中,有海水的混入。综合判断,渝南地区中二叠世梁山期的沉积环境为淡化渴湖无疑。在此基础上以岩性相为依据,可以将含矿岩系划分为7种微相类型：泥状铝土岩微相（MF-1）、高岭石粘土岩微相（MF-2）、绿泥石粘土岩微相（MF-3）、菱铁矿微相（MF-4）、豆状铝土岩微相（MF-5）、鲕状铝土岩微相（MF-6）、砾屑状铝土岩微相（MF-7）。这些微相可以组合为渴湖滨湖、潟湖浅湖和潟湖深湖三种亚相。通过对收集的剖面资料的研究,编制了大佛岩铝土矿岩相古地理图,该图显示研究区总体地形北高南低,沉积相带呈有规律展布,沉积相带展布受水体深度控制。通过平面和纵向上Al₂O₃含量和沉积微相的对比,发现代表潟湖滨湖亚相和渴湖浅湖亚相的沉积微相Al₂O₃含量高于代表渴湖深湖亚相的沉积微相,渴湖滨湖亚相和潟湖浅湖亚相是铝土矿成矿的有利相带。电子探针和能谱分析发现含矿岩系豆粒和假鲕粒有铁质包壳,证明风化作用在铝土矿形成中的作用,但沉积学证据证明以大佛岩铝土矿为代表的渝南铝土矿为沉积型铝土矿,风化作用形成的原始红土型铝土矿被水流搬运到淡化渴湖环境沉积成矿。更多还原

【Abstract】 By the influence of Guangxi movement, the yangtze plate rise to land. Experienced more than100Ma’s weathering and erosion from middle permian to middle silurian. On this condition, the South Chongqing Bauxite was formed. In order to supply some basic research date for the exploration of bauxite, this paper take Dafoyan Bauxite as a representative mining area, to research its sedimentary micro-facies and lithofacies paleogeography.The regional sedimentary study found that the bauxite bearing rock series has three different profile structures. The northern part of this region shows freshening lagoon sediment, and Dafoyan Bauxite is located in the north margin of the freshening lagoon. The middle and the Northern-Eastern part shows barrier sand bar sediment. And the southern part is normal shallow sea sediment.The lithology analysis study of the bauxite bearing rock series indicate that sedimentary fabric of river, shore lake and shallow lake are formed in the rock series. The profile shows continuous change of water depth. The sporo-pollen identification reflects warm, wet and fresh water sedimentary environment. The trace elements analysis reflect it’s mainly fresh water sediment, and sometimes intruded by sea water. Synthetical judged, the sedimentary environment of Dafoyan Bauxite is freshening lagoon without doubt. On this basis, according to the lithologic features, we classified the auxite bearing rock series into seven micro-faces. Which are Muddy aluminous micro-face (MF-1), Kaolinite clay micro-face (MF-2), Chlorite clay micro-face (MF-3), Siderite micro-face (MF-4), Pisolite shape aluminous micro-face (MF-5), Oolite shape aluminous micro-face (MF-6), Clastic aluminous micro-face (MF-7). All these micro-face can be combined into Shore lagoon sub-fase, Deep lagoon and Shallow lagoon sub-fase.By collecting and studying profile datas in drill bores and trenchs, we compiled lithofacies paleogeography map of Dafoyan Bauxite. The lithofacies paleogeography map shows the terrain of Dafoyan in Liangshan period is north higher than south. The sedimentary facies belts are Spreading regularly. The sedimentary facies belts Spreading type is controlled by water depth and terrain of the area. The comparison of horizontal and vertical both indicate that the sedimentary micro-faces which belong to Shore lagoon and Shallow lagoon sub-face contain higher Al2O3than the sedimentary micro-faces which belong to Deep lagoon sub-face.Electron microprobe and energy spectrum analysis found the pisolites and false oolites in the bauxite bearing rock series have ferruginous cladding. This is a evidence of weathering process in the formation of Bauxite. But sedimentary evidence shows Dafoyan bauxite is sedimentary type bauxite. The weathering process just formed the original red-soil type bauxite. The original red-soil type bauxite was carried in the freshening lagoon by water steam.更多还原