Geochemical Characteristics Of Ningxiang-type Iron Deposits In The West Of Hubei Province And Their Implication For Metallogenic Environment

The west of Hubei province is the most concentrated area of Ningxiang type iron deposits. This article selects Huoshaoping iron deposit, Longjiaoba iron deposit and Guandian iron deposit in west Hubei province as the research subjects. On the basis of field work, we focused on some issues such as the geochemical characteristics indicative function of metallogenic environment, source of ore-forming materials,ore-forming processes and ore deposit genesis through the study of the main and trace elements test of ores, lithofacies paleogeographic conditions analysis, the ancient climate analysis. And collecting geochemical datas of Xuanlong type iron deposits to compare the similarities and differences between them.Ningxiang type iron deposits have four layers of iron ore, Fe1 and Fe2 are hosted in upper Devonian Huang jiadeng group, the ore mineral is oolitic hematite, this layers are small scale. Fe3 and Fe4 are hosted in upper Devonian Xie jingsi group, the ore mineral of Fe3 is oolitic hematite, this layer is the main seam of most Ningxiang type iron deposits. the ore mineral of Fe4 are oolitic hematite, magnetite, chamosite and siderite, this layer is the main seam of several Ningxiang type iron deposits.Ningxiang type iron deposit samples, the major elments of iron ores are mainly composed of Fe2O3,SiO2 and Al2O3,and have distinct Zn, V positive anomalies and Nb,Ta, Rb, Ba negative anomalies. the content of Zr,Sc and Th are enrichment. The total concentrations of rare earth elements(REE) are high. and appeared LREE relative loss, HREE relative enrichment distribution patterns, Longjiaoba iron deposit and Guandian iron deposit appear MREE relative enrichment, with la, Eu weak positive anomalies, Y weak negative anomaly, a slight positive Eu anomaly.In the Middle-Late Devonian, the west of Hubei province belong to intracontinental basin, surrounded by ancient land. In hot and humid climates, the ancient land rocks occur laterization and provide terrigenous for iron mineralization.With the transgression of Huanan ocean, they were taken into the basin, iron deposits are mainly formed in the western basin near-shore and far-shore phase deposition environment. Ore with the feature of phosphorus and vanadiumenrichment. This reflects biological components are added to the ore-forming process,rich biological ingredients can provide adequate protection in the form of colloidal iron glues migration process. Comprehensive geochemical characteristics, this paper argues that the formation process of Ningxiang type iron deposits have nothing to do with hydrothermal activity, should belong to the colloid chemical sedimentary deposits.