贵州省务正道地区铝土矿地球化学特征及意义

Geochemical Characteristics of Bauxite in the Wuzhengdao Area,Guizhou Province

务正道地区是中国重要的铝土矿区,本文对该区各类矿石、赋矿围岩及基底层（韩家店组S1-2hj）进行主、微量及稳定同位素研究。结果表明,基底层中Al2O3含量低于赋矿围岩及矿体,但明显高于其他地层,从基底层→赋矿围岩→豆鲕状、碎屑状铝土矿→土状铝土矿,Al2O3、Ti O2、K2O含量升高,Si O2含量降低;Rb、Ba、Sr、Cs、Ni等表现为亏损,Li、Be、V、Cr及高场强元素Nb、Ta、Zr、Hf、Th、U等主要表现为富集。各类矿石、赋矿围岩与基底层稀土配分型式相似,均为LREE富集、δEu〈1、δCe〉1;δ34S为-29.2‰~19.35‰,分布范围较广,具多样性,含海水硫、生物硫及幔源硫。结合成矿背景、地质地球化学特征等,认为该区铝土矿成矿物质直接来源为基底层韩家店组,最终来源为上地壳硅酸盐岩类物质,矿床成因类型主要为风化-沉积型,成矿环境主要为滨浅海-潟湖（海陆交互）环境。

There are significan bauxite resources in the Wuzhengdao area,Guizhou,China.A study on major and trace elements and stable isotopes of various kinds of ores,ore-bearing walrocks,and the basement startum（the Hanjiamiao Formation S1-2hj） has been carried out in this paper.Results show that Al2O3 contents of thebasement stratum（S1-2hj） are lower than those of ores and ore-bearing wallrocks,but obviously higher than those of other strata.From the basement stratum,to orebearing wallrocks,oolitic bauxite ores,to earthy bauxite ores,their contents of Al2O3,Ti O2,and K2 O are increased,but Si O2 contents are decreased,their Rb,Ba,Sr,Cs,and Ni are depleted,but their Li,Be,V,Cr,Nb,Ta,Zr,Hf,Th,and U are mainly enriched.Various kinds of ores,ore-bearing wallrocks,and the basement stratum（S1-2hj）have similar REE distribution patterns,with LREE enrichment,δEu 1,δCe 1,and δ34S values widely varying from-29.2‰ to 19.35‰,indicating various sulfur sources including seawater,biogenic and mantle sulfurs.Combing with the geological background and geochemical features of the mineralization,it is believed that the ore-forming materials of the bauxite deposits in the area could be directly sourced from the basement stratum of the Hanjiadian Formation（S1-2hj）,which were originated from the silicates of the upper crust.These deposits belong to the weathering-sedimentary type of deposits which were formed mainly in the environments of shallow sea and lagoon.