黔北沉积型铝土矿鲕粒成因

Origin of oolites of sedimentary bauxite in northern Guizhou,China

通过野外地质调查、手标本观察、岩石光面分析、偏光显微镜观察、XRD分析、扫描电镜分析等手段对黔北务川−正安−道真地区(务正道)铝土矿中的鲕粒进行了系统研究。结果表明:铝土矿含矿岩系中鲕粒按成分可分为铝土质鲕粒、绿泥石鲕粒、硬水铝石鲕粒、赤铁矿鲕粒、黄铁矿鲕粒;铝土矿中的粗碎屑颗粒为盆地内部形成的内碎屑,泥质粗碎屑颗粒并不反映高能环境,铝土矿中的硬水铝石为常温常压条件下形成;除部分赤铁矿鲕粒外,大部分铝土矿中的鲕粒为低能条件下或淋滤过程中在孔隙中原位形成,绿泥石与硬水铝石交替凝聚形成核心和同心层;持续的淋滤作用会破坏鲕状构造,鲕状矿石向碎屑状或半土状矿石转变,使铝土矿品质进一步提高。

By means of field geological investigation,hand specimen observation,rock smooth surface analysis,polarized light microscope observation,XRD and SEM analysis,the oolites in Wuchuan-Zheng’an-Daozhen area(WZD)in northern Guizhou,China,were systematically studied.The results show that,according to the composition,the oolites in bauxite ore-bearing rock system can be divided into aluminous oolite,chlorite oolite,diaspore oolite,hematite oolite and pyrite oolite.The coarse clastic particles in bauxite are the internal clasts formed in the basin,while the argillaceous coarse clastic particles do not reflect the high energy environment.The diaspore in bauxite was formed under normal temperature and pressure.In addition to some hematite oolites,most of the oolites in bauxite formed in situ in the pores under the condition of low energy condition or leaching process,and chlorite and diaspore alternately agglomerated to form the core and concentric layer structure.Continuous leaching destroyed the oolitic structure,and transformed the oolitic bauxite ore to clastic or half-earthy ore,further improved the quality of bauxite.