Genesis Of The Rencun Bauxite Deposit,western Henan,China

The bauxite in Henan is hosted in the middle-low member of Benxi formation in Carboniferous strata and above the fossil erosion surface of middle Ordovician carbonatite,it is typical of karst bauxite.Rencun bauxite is located in the west of Henan,it belongs to Nandiwu-Duancun-Leigou metallogenic belt of Mianchi metallogenic province.The research area is located in the north by east of Duancun,and it belongs to the dipper control area.Ore-bearing horizon sequence in the research area is generally in order from bottom to top:underlyingpyrite bearing carbonate,pyrite bearing bauxitic mudstone,siderite bearing bauxitic mudstone,sandy/porus/oolitic bauxite,bauxitic mudstone,massive bauxite,bauxitic mudstone,coal line and roof sand stone.Mineral composition of ore bearing profile main includes diaspore,illites,anatases,pyrites,siderites,and includes a small quantity of chlorites,rutile,zircon and svanbergite.Geochemical analyses revealed that Al₂O₃,SiO₂ and LOI are the main components of the bauxite ores,iron content is relatively low.B and Bi are relatively enriched compare to upper crust,but Ba and Zn are depleted.Siderophile elements such as V and Sc,high field strength elements such as Zr,Hf,Nb,Ta,and radioactive elements such as U and Th in bauxite layer are more enrichment than others.REE distribution pattern shows right deviation,LREE are obviously enriched.Eu negative anomaly and positive anomaly of Ce in bauxite layer.Eu/Eu*-TiO₂/Al₂O₃ diagram,Cr/Zrand Th/U,trace and rare earth elements distribution pattern and speciation analysis of placer minerals suggest that bauxite ore-forming materials includes north Q inling igneous,aluminium silicates near the old land and the bottom plate carbonate.Mineralogical and geochemical characteristics ofbauxite suggest that Rencun bauxite deposited in the reduction condition.The process of bauxite formation includes terrigenous period,sedimentary period,minerlization period and post minerlization period,bauxite was forming during the minerlization period and post minerlizating period.