云南文山县天生桥铝土矿地球化学特征与物源分析

Geochemical Characteristics and Provenance Analysis of the Tianshengqiao Bauxite in Wenshan County,Yunnan Province

云南文山县天生桥地区铝土矿是典型的沉积型铝土矿,矿体赋存于上二叠统龙潭组,其下伏地层为上石炭统灰岩或与峨眉山大火成岩省有关的玄武岩。矿石以泥晶结构为主,含少量粒屑结构与鲕粒结构;矿石的结构特征表明风化物质可能经过短距离的搬运。常量元素分析结果显示铝土矿石中Al2O3分别与Fe2O3和TiO2具有较好的负相关关系。在铝土矿矿化过程中,微量元素Zr、Hf、Nb、Ta和Bi相对于Li、Rb、Sr、Ba不断富集。元素Zr、Hf、Nb、Ta分别与TiO2显示较高的相关性。运用稳定元素相关性(如Zr-Hf、Nb-Ta)、lgNi和lgCr二元图解以及稀土元素配分模式等方法探讨矿床成矿物质来源,研究结果表明玄武岩为铝土矿的形成提供了主要的物质来源,下伏碳酸盐岩可能也提供了少量的物质来源。

The Tianshengqiao bauxite deposit in Wenshan County,Yunnan is a typical sedimentary bauxite de-posit.The ore bodies occur in the Upper Permian Longtan Formation,which is underlain by the Upper Carboni-ferous limestones and the basalt related to the Emeishan LIP.The ore is dominated by pelitomorphic textures, with a few detrital textures and ooidic textures.These textural features suggest that the bauxitic soils were trans-ported over a short distance.Constant elements analysis reveals that Al2 O3 of bauxite has a negative relationship with Fe2 O3 and TiO2 .Trace elements such as Zr,Hf,Nb,Ta and Bi were enriched during the bauxitization process more than Li,Rb,Sr,Ba.Elements of Zr,Hf,Nb and Ta demonstrate significant correlation with TiO2 respectively.Studies of stable elements correlation such as Zr-Hf,Nb-Ta,bivariate plots of lgNi and lgCr, and REE pattern suggest that the basalt is the major source of materials for the bauxite formation.Meanwhile, the carbonate rocks may provide a small amount of source of materials for the formation of bauxite ores.