滇东南上二叠统吴家坪阶下部铝土矿地球化学特征及物源分析

Geochemical Characteristics and Material Source of Bauxite Ores from the lower Wuchiapingian of Upper Permian in Southeastern Yunnan Province

滇东南地区上二叠统吴家坪阶下部铝土矿不整合于峨眉山玄武岩或灰岩之上,查明其物质来源对铝土矿勘探具有重要意义。对铝土矿及峨眉山大火成岩省玄武岩、花岗岩及下伏灰岩的地球化学指标进行研究,结果表明:滇东南铝土矿常量元素主要由SiO2、Fe2O3、Al2O3、TiO2和FeO组成;铝土矿中富集Zr、Hf、Nb、Ta元素,表明Zr、Hf、Nb、Ta等高场强元素在滇东南地区铝土矿矿化过程中较为稳定,且Zr、Hf、Nb、Ta表现出良好的相关性;铝土矿球粒陨石标准化曲线与峨眉山玄武岩配分曲线趋势一致,均富集轻稀土元素,而与下伏灰岩差异较大,且Zr-Hf、Nb-Ta图解与峨眉山玄武岩呈线性关系,而与矮郎河过铝质花岗岩的相关性不强。据此推断滇东南地区上二叠统吴家坪阶下部铝土矿主要物质来源为峨眉山玄武岩。

The bauxite deposit in southeastern Yunnan province overlies unconformably on either Emeishan basalts or carboniferous limestones. It makes sense to clarify the material souree of bauxite ores for its exploration and development. The geochemical characteristics of the bauxite ores,granite, basahs and limestone were studied in detail. Geochemical analyses indicate that the main components in the ores are A1203 , Fe203 , SiO2 and TiO2 and other elements oceur in quantities not substantial to affect the quality or processing of the bauxite. Trace elements like Zr, Hf, Nb, and Ta were obviously enriched during the bauxitization. Furthermore,elements such as Zr, Hf, Nb and Ta exhibit signifieant eorrelation with each other. Chondrite-normalized REE patterns of the bauxite indicates that bauxites are similar to Emeishan basalts,but are different from the underlying limestone. Besides,bauxites have the similar primitive-mantle-normalized pattern and upper-continental-ernst-normalized pattern of trace elements as Emeishan basahs,but show distinct patterns from limestone. Simultaneously, geochemical indiees such as Zr/Hf and Nb/Ta denote that the magmatic rocks related to the Emeishan basalts pro- vided the main sources of material for the bauxite ores.