柬埔寨上川垅铝土矿是典型的风化淋滤红土型铝土矿床,规模大,质量好,是中南半岛红土型铝土矿带中的重要矿床,但研究程度低,目前未见其地球化学研究报道.本文通过对比研究两个风化程度不同的矿点以及下伏玄武岩的主要成分和稀土元素地球化学特征,探讨其对本区铝土矿成因的指示意义.研究表明:该区铝土矿石的稀土含量小(ΣREE=34.22×10-6~102.17×10-6,局部出现225.92×10-6),成矿过程发生迁移,分布不均匀.轻重稀土比值LΣREE/HΣREE较大,为4.73~22.73,(La/Yb)N为5.61~36.22,轻重稀土分馏明显,呈轻稀土富集特征,且风化程度越强,分馏越明显.稀土配分模式曲线呈平缓右倾型,Eu呈弱正异常(1.04~1.11),两矿点Ce异常有所差异,低风化程度与弱负异常对应,高风化程度与弱正异常对应;稀土元素配分模式曲线图、δEu值及δEu与TiO2/Al2 O3图解共同提供了铝土矿下伏玄武岩为成矿物质来源的地球化学依据;两矿点Al2 O3含量显示,风化作用越彻底,Al含量越高,矿石质量越好.%The Kirirom bauxite deposit ,as a typical weathering-leached lateritic bauxite deposits ,with the characteristics of large reserve and good quality ,is an important deposit in indochina peninsula lateritic bauxite belt .There has no publishes about its elemental composition due to the low degree of geological study .Reported here are the main elemental composition and rare earth elements (REE ) data of two different weathering occurrences and their underlying basalts ,to discuss the genesis of bauxite in this area . The results show that ,the bauxite ores have a character of low REE content in general (ΣREE=34 .22 × 10-6 ~ 102 .17 × 10-6 ,locally 225 .92 × 10-6 ) ,and the metallization shows elements migration with an uneven distribution .The LREE/HREE values (4 .73~22 .73) and (La/Yb)N values (5 .61~36 .22) are high ,the fractionation of LREE and HREE is obvious ,shows LREE enrichment ,and the stronger the weathering ,the more obvious fractionation .The REE distribution pattern is characterized by flat right inclining type with weak Eu positive abnormal (δEu=1 .04~1 .11) ,and the difference of Ce abnormal in different occurrence shows as that the weak negative Ce abnormal in less weathering occurrence and weak positive Ce abnormal in stronger weathering occurrence .Similar REE distribution patterns and δEu between bauxite and basalt as well as theδEu-TiO2/Al2 O3 graphic indicate that the basalts are the material source of bauxite ore in this area ;The stronger weathering occurrence shows high contents of Al2 O3 ,indicates that grade and quality of the bauxite is closely related to the weathering progress .
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