黔中地区蔡家坝铝土矿床富锂铝土岩地球化学特征及沉积环境研究

Geochemical Characteristics and Sedimentary Environment of Li-Rich Bauxite in the Caijiaba Bauxite Deposit,Central Guizhou Province

贵州清镇蔡家坝铝土矿床是近年来在黔中铝土矿成矿区内新发现的铝土矿床之一,铝土矿体呈层状及似层状产于下石炭统九架炉组地层中。本研究通过对蔡家坝铝土矿床中以铝土岩为主的含铝岩系钻孔岩心剖面开展详细的矿物学和地球化学研究,发现含铝岩系中的铝土岩明显具有Li超富集的现象。研究结果表明,含铝岩系的所有样品中均富含高浓度的Li(210~2480)×10^(-6);其中,10件铝土岩的Li含量为(210~2480)×10^(-6)(平均1198.9×10^(-6)),3件铝土矿石的Li含量为(412~1440)×10^(-6)(平均980.7×10^(-6)),表现出明显超富集的特征。光学显微镜和XRD分析显示,富锂铝土岩主要由伊利石、高岭石和绿泥石组成,以及少量的硬水铝石、勃姆石、黄铁矿、锐钛矿等。结合矿物学和地球化学证据,研究区铝土岩中的Li主要赋存在高岭石和伊利石等粘土矿物中,当铝土岩中Al_(2)O_(3)含量介于30%~40%之间以及Al_(2)O_(3)/SiO_(2)比值介于1~1.5时,铝土岩中的Li最为富集。元素地球化学分析表明,研究区内的富锂铝土岩形成于温暖潮湿和相对氧化的陆相淡水环境。

The Caijiaba bauxite deposit in Qingzhen,Guizhou is one of the newly discovered bauxite deposits in the central Guizhou bauxite deposit area in recent years.The bauxite deposits were layered and quasi layered,and occurred in the Lower Carboniferous Jiujialu Formation.This study conducted detailed mineralogical and geochemical studies on the core profiles of aluminum bearing rock series in the Caijiaba bauxite deposit.The aluminum bearing rock series in the Caijiaba bauxite deposit exhibits obvious Li hyperaccumulation.The research results indicate that all samples of aluminum bearing rock series contain high concentrations of Li(210~2480)×10^(-6).Among them,ten pieces of bauxite rock have Li content of(210~2480)×10^(-6)(average 1198.9×10^(-6)),and three bauxite ores contain Li content(412~1440)×10^(-6)(average 980.7×10^(-6)),showing obvious super enrichment characteristics.Optical microscopy and XRD analysis show that the lithium rich bauxite rock was mainly composed of illite,kaolinite,and chlorite,as well as a small amount of hard alumina,boehmite,pyrite,and rutile.Based on mineralogical and geochemical evidence,Li was mainly present in clay minerals such as kaolinite and illite in the study area.When the Al_(2)O_(3)content in bauxite ranges from 30%to 40%and the Al_(2)O_(3)/SiO_(2)ratio ranges from 1 to 1.5,Li was most enriched in bauxite.Element geochemical analysis shows that the lithium rich bauxite rocks in the study area were formed in a warm,humid,and relatively oxidized terrestrial freshwater environment.