黔东南铝土矿含矿岩系镁铝铁结构及地球化学特征

黔东南铝土矿赋存于下二叠统梁山组,其含矿岩系具有沉积型铝土矿典型的"煤-铝-铁结构",即下部发育铝质页岩夹菱铁矿结核,中部由含铝岩组夹多层豆状或土状铝土矿组成,上部由碳质页岩、砂岩夹煤层组成。沉积环境为海陆交互相-滨海边缘沼泽相,具有稳定的构造背景。通过含矿岩系物质组成结构分析和元素地球化学研究认为:"煤-铝-铁结构"在铝土矿中的普遍出现,是沉积型铝土矿在矿化过程中物理化学环境多变导致的深度去硅去铁作用,加之外部环境提供充足的有机质物质来源,从而形成的非偶然结果。因此,含矿岩系的分层结构形成过程中的物理化学变化所导致的多种地质异常可作为找矿实践中的成矿标志。

The coal-bauxite-iron structure and geochemistry feature of ore-bearing rock series for bauxites in southeast Guizhou

The depositional bauxite in southeast Guizhou is hosted within the Lower Permian series liangshan group. And the ore-bearing rock series shows the typical coal-bauxite-iron structure which includes the aluminum shale intercalated within siderite tuberculosis, aluminiferous rock association intercalated within multiple-layer pisolitic or earthy bauxite, and carbonaceous shale and sandstone intercalated within coal from the lower to the upper in the profile of bauxite. Presumably, the sedimentary environmentb belongs to marine-terrigenous facies to coastal-swamp facies. Mineralogical and geochemistry analyses reveal that coal-bauxite-iron structure appears generally in the sedinentrary bauxite, which is caused by the changes of the physical and chemical environment. Acid and alkali conversion that leads to deeply leaching Si and Fe, and sufficient organic matter give rise to the noncontingentevent together. Therefore, hierarchical structure of ore-bearing which caused by the change of physical and chemical environment can be used as prospecting criteria for bauxites.