广西扶绥县沉积型铝土矿床地质特征与成矿模式

Geological characteristics and metallogenic model of sedimentary bauxite deposits in Fusui County,Guangxi

广西扶绥地区沉积型铝土矿矿石矿物特征表明,该铝土矿床的形成环境与海相相关性不太强烈,与陆相沉积环境相关性更高。其矿石主要化学组分为Al_(2)O_(3)、SiO_(2)、Fe_(2)O_(3)、灼失量及S,Al_(2)O_(3)与SiO_(2)、Fe_(2)O_(3)呈负相关关系,而与烧失量和矿层厚度正相关性不明显;S与Al_(2)O_(3)呈不相关关系,表明S可能为后期带入。该地区铝土矿矿石的化学蚀变指数(CIA)接近100,指示受到强烈化学风化作用,对应炎热、潮湿的气候条件。沉积型铝土矿体上覆围岩岩性较为复杂,有(炭质)泥岩、煤(层)线亦有灰岩地层,合山组含矿岩系自下而上揭示了沉积环境从陆相到海相的变化。沉积型铝土矿成矿过程可分为红土化作用、沉积—成岩作用和氧化淋滤作用三个主要阶段。

The mineral characteristics of sedimentary bauxite deposits in Fusui County of Guangxi shows that the forming environment of bauxite is not closely related to the marine phase,but more related to the continental phase.The main chemical compositions of ores are Al_(2)O_(3),SiO_(2),Fe_(2)O_(3),loss of ignition and S.And the content of Al_(2)O_(3)is negatively correlated with the contents of SiO_(2),Fe_(2)O_(3),but not positively correlated with loss of ignition and thickness of ore bed.Bauxite CIA is up to 100 in this area,indicating strong chemical weathering intensity,and corresponding to the hot and humid climate.The overlying rocks of sedimentary bauxite are complex,including(carbonaceous)mudstone,coal(seam)line and limestone.The change of sedimentary environment from continental to marine phases is recognized by the ore-bearing rock series of Heshan Formation from bottom to top.The mineralization process of sedimentary bauxite can be divided into three main stages,lateralization,sedimentary diagenesis and oxidation leaching stage.