摘要
黔北铝土矿以特有的古喀斯特形态和矿石风化结构显示了它的古喀斯特风化成因。笔者进一步从矿床剖面结构、矿物成因类型、硬水铝石的氢、氧稳定同位素特征及母岩物质组成等方面的深入研究,揭示了在其形成过程中经历了早石炭世红土化作用阶段的特点;以脱硅和排铁作用为主的各种成矿作用,为铝土矿的最终形成,造成了良好的时空环境。
Bauxite deposits are widely distributed in northern Guizhou and southeastern Sichuan. The bauxite occurs in stratoid, lenticular, dishlike, and pocket or sinkhole-funnel like and other irregular forms in the Early Carboniferous alumino-ferric clay layers. The thickness or width of the 'orebodies' is mostly in the range of 0.2 to 12.0m, with a maximum of 48.8 m. The Al_2O_3 and Fe_2O_3 contents of the bauxite are usually over 60% and 3—5% respectively and that of latter may be as high as >20%. The principal Al-mineral is diaspore, whose content may be up to 80%; others are alumogel and boehmite and also gibbsite. Main textures piso-oolitic, granular and clastic textures.Parent materials of the bauxite are mainly of lateritic nature formed by weathering and leaching of the Cambrian or/and Ordovician limestones, argillaceous limestones and shales. On the basis of a large number of analytic data, diaspore may be classified into three genetic types i.e. palaeoweathering authigenic type, pataeosupergene type and epigenetic type, of which the first one accounts for the largest proportion. The parent materials producing bauxite minerals underwent a series of bauxite forming processes which include early-desilication, hydrolytic desilication, gelified desilication, initial iron-separation, eluvial iron-separation, late iron-separation, supergene iron-separation, ferrallitization, mature bauxitisation, high-grade bauxitisation, primary redeposition and secondary redeposition. In the counse of these complex mineral evolutionary processes, kaolinite and illite were transformed into diaspore through a series of intermediate stages such as those of the formation of montmorillonite, halloysite and alumino-ferric colloids, they constitute a karst-related bauxite mineral evolutionary sequence peculiar to the bauxites of northern Guizhou.The for mation of the bauxite deposits of various sizes depend on the morphology of palaeokarst and all the relevant textures show their palaeoweathering origin Diaspore, belongs to the palaeowe
出处
《地质学报》
EI
CAS
CSCD
北大核心
1990年第3期238-247,T001,共11页
Acta Geologica Sinica
