摘要:
丘北飞尺角铝土矿床是云南近年新发现的具大型规模的铝土矿床.针对矿区沉积型铝土矿(岩)石、下伏灰岩和玄武岩进行了主、微量和稀土元素研究结果表明:铝土矿(岩)主量元素主要由Al2O3、SiO2、TFeO和TiO2组成,具高铁、中硅、低铝特点.铝土矿(岩)Al/Si(0.69~5.19)、Al/Ti(5.01~29.47)比值与下伏灰岩(Al/Si=0.65~1.33,Al/Ti=3.53~14.32)接近,Harker图显示玄武岩与铝土矿(岩)线性关系更为显著,表明铝土矿(岩)物源具多源性特点,灰岩和玄武岩均有贡献.铝土矿(岩)微量元素富集高场强元素(Th、Nb、Zr、Hf和Ti)与下伏玄武岩相似.在Zr-Ti图上铝土矿(岩)相对集中分布在玄武岩区及其附近.铝土矿(岩)稀土元素配分曲线缓右倾、稀土总量、δCe值与玄武岩相近.在LogCr-LogNi和w(La)/w(Yb)-w(REE)图上铝土矿(岩)分布接近玄武岩区而远离碳酸岩区.铝土矿(岩)具正Ce异常,中等Th/U和高Sr/Ba比值特点.综合岩石学、地球化学和成矿地质背景分析认为飞尺角铝土矿(岩)是在富氧的海相环境下由沉积作用形成,其下伏玄武岩为成矿提供了主要物源,灰岩贡献很少.
Abstract:
The Feichijiao bauxite deposit in Qiubei City of Yunnan Province is a newly discovered large-size bauxite deposit. A study of major and trace elements and REE of the sedimentary bauxite ore (rock), underlying limestone and Emeishan basalts was carried out in this paper. The result shows that the major components are Al2O3, SiO2, TFeO and TiO2. The sedimentary bauxite ore (rock) is characterized by high iron, intermediate content of silicon and low aluminum. Al/Si ratios (Al/Si=0.69~5.19) and Al/Ti ratios (Al/Ti=5.01~29.47) of sedimentary bauxite ore (rock) are close to Al/Si ratios (Al/Si=0.65~1.33) and Al/Ti ratios (Al/Ti=3.53~14.32) of the underlying limestone respectively, and the linear relationship between basalts and bauxite ore (rock) is more significant on the Harker diagram of oxide, which indicates that the source of bauxite had multi-source characteristics, with the underlying limestone and basalt making some contribution. Trace element spider diagram shows that bauxite ore (rock) enrichment of HFSE (Th, Nb, Zr, Hf and Ti) is similar to that of the underlying Emeishan basalts. The bauxite ore (rock) spots are relatively concentrated in the basalt distribution area and its vicinities. REE patterns as well asΣREE and Ce anomalies of bauxite ores are similar to those of basalts, and they display positive Ce anomalies, moderate Th/U ratios and high Sr/Ba ratios. The petrological, petrogeochemical and metallogenic backgrounds suggest that the sedimentary bauxite ore (rock) was formed by sedimentation in an oxygen-rich marine environment, and the underlying Emeishan basalt provided the major materials for the formation of bauxite ore (rock), with the underlying limestone contribution making insignificant contribution.
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