山西省石墙区铝土矿地质与地球化学特征研究

Geologoical and Geochemical Characteristics of the Shiqiang Bauxite Deposit in Shanxi Province

山西省原平市石墙区铝土矿属于典型的喀斯特型铝土矿。含矿岩系自下而上包括铁质粘土层、铝土矿层、粘土层,且含矿岩系一般包含两个明显的沉积旋回。矿体主体呈层状、似层状产出,矿石结构以隐晶质结构为主,局部出现碎屑和豆鲕粒结构。矿石构造大都为块状构造。矿物学分析显示,硬水铝石、针铁矿、锐钛矿、高岭石是主要的组成矿物,另外还含有石英、伊利石、绿泥石等矿物。地球化学分析显示,主量元素主要包括Al2O3、SiO2、Fe2O3、H2O+及TiO2,微量元素中碱性和碱土元素Li、Sr、Be、Cs、Ba及酸土元素Zr、Hf、Nb、Ta、W均表现为明显富集,且Zr和Hf之间以及Nb和Ta之间具有高度的相关性。地球化学指标Zr/Hf、Nb/Ta以及Eu/Eu*-TiO2/Al2O3图解显示,底板碳酸盐岩是山西省原平市石墙区铝土矿的重要源岩。

The Shiqiang bauxite deposit in Yuanping City of Shanxi Province is a typical karst one. The ore-hosted strata are ferruginous clay layer, bauxite layer and clay layer in an upward sequence, which comprise two obvious sedimentary cycles. The orebodies mainly occur as stratified or stratoid beds and the ore textures are predominantly cryptocrystalline with elastic or oolitic texture being locally present. The massive structure is dominated in bauxite ores. Mineralogical analysis reveals that diaspore, goctbite, analase and kaolinite are the major minerals in bauxite ores with small amounts of quartz, illite and chlorite. Geochemical analyses indieate that Al2O3 , SiO2 , Fe2O3 , H2O＋ and TiO2 are the main components of the bauxite ores, and trace elements such as alkaline and alkaline earth elements Li, Sr, Be, Cs, Ba and acid earth elements Zr, Hf, Nb,Ta, W were significantly enriched during the banxitization process. In addition, Zr vs. Hf and Nb vs. Ta show a high degree of correlation. The diagram of geochemical indexes such as Zr/Hf, Nb/Ta and Eu/Eu ＊ -TiO2/Al2O3 illustrates that the carbonatite is the primary material source of the bauxite ores in this deposit.