桂西田阳堆积型铝土矿矿物学及地球化学

摘 要]桂西田阳堆积型铝土矿产于第四纪红土层中。本文通过对桂西田阳第四系堆积型铝土矿进行一系列矿物学与地球化学研究,探索铝土矿的物质来源。矿物学分析显示铝土矿石中主要矿物为硬水铝石、赤铁矿和锐钛矿,含有少量高岭石、鲕绿泥石、三水铝石、针铁矿、金红石、伊利石、蒙脱石和石英等。地球化学分析显示,组成铝土矿石的主要化学组分有Al₂O₃、Fe₂O₃、SiO₂、TiO₂、FeO 和H₂O⁺;微量元素分析显示,铝土矿石相对地壳和原始地幔富集B、Li、Ga、Zr、Hf、Nb、Ta、W、Th、U 等元素,而亏损Ni、Cr 等元素。矿石中明显富集稀土元素,稀土总量变化大,轻重稀土分异明显,轻稀土元素富集明显;矿石具有明显的铈异常和铕异常,且铕异常相对稳定,为一致的负异常。元素相关性分析显示常量元素间相关性较差;部分微量元素如Zr、Hf、Nb 和Ta 间呈现出较高的正相关性。通过Zr/ Hf、Nb/ Ta 图解、Eu/ Eu* - TiO₂/ Al₂O₃图解和Zr-Cr-Ga 图解综合分析显示铝土矿物质来源复杂,底板碳酸盐岩和周围火成岩都为铝土矿提供物源。

Mineralogy and Geochemistry of the Tianyang Accumulation-type Bauxite in Western Guangxi Province

The Tianyang accumulation-type bauxite deposit in western Guangxi Province is located in the Quaternary ferrallitic soil beds.This work has made mineralogical and geochemical studies of the Tianyan accumulation-type bauxite to reveal the source material for the bauxite ores in this area.Mineralogical analyses show that diaspore,hematite and anatase are the main mineral components of the bauxite ores,with small amount of kaolinite,oolite chlorite,gibbsite,goethite,rutile,illite,montmorillonite and quartz.Geochemical data indicate that the main components are Al2O3,Fe2O3,SiO2,TiO2,FeO and H2O+.Trace element analysis shows that the bauxite ore is enriched in B,Li,Ga,Zr,Hf,Nb,Ta,W,Th and U,but lack of Ni and Cr compared with crust and original mantle.Ores are enriched in REE,∑REE is greatly changed,HREE and LREE differentiate,and LREE are significantly enriched.Ores display obvious Ce and Eu anomalies,and Eu anomalies are negative and relatively stable.Correlative analysis of the elements shows that the major elements are with low correlation,and some trace elements such as Zr,Hf,Nb and Ta show a strong correlation.Geochemical indices such as Zr/Hf and Nb/Ta,Eu/Eu*-TiO2/Al2O3 and Zr-Cr-Ga indicate that the source of material for bauxite ores is complex,and the underlying carbonate and surrounding igneous rock provided material for the formation of the bauxite deposit.