The Material Composition And Enrichment Regularity Of Mianchi Bauxite Field, Henan Province, China

The Mianchi bauxite field is one of the important bases of bauxite resources in henan province. All of the Bauxite deposits are above karst surface of Ordovician carbonatite and hosted within the middle-low member of the Carboniferous Benxi formation. That is the typical representative of karstic-type bauxite in China. Then, the shape, scale, and grade of the bauxite orebody are closely related to the paleo-karst landform. After formation of bauxite layers, it could be folded by superimposed folds. It makes our understanding of bauxite Metallogenic regularity and the exploration for hidden bauxite deposits become more difficult.Base on the field survey and a lot of research of the ore-bearing rock series. The results show that sequence of the ore-bearing rock series is not only affected by the bottom paleo-karst landform, but also controlled by the regional tectonic, magmatic intrusion and sedimentary environment. The sequence of the ore-bearing rock series in different bauxite deposit is obviously different. There are also differences in the sequence of the ore-bearing rock series of different paleo-karst depressions in the same deposit. The minerals in bottom of the outcrop ore-bearing rock series is mainly hematite, and the hidden ore-bearing rock series is characterized by siderite. The major minerals in the middle unit of the ore-bearing rock series include diaspore, kaolinite, illite and a small amount of anatase. Cryptocrystalline is the major texture of bauxite ore, with much less oolitic and clastic textures.The characteristics of bauxite in Mianchi bauxite field with high aluminum, high silicon and low iron. The trace element content is controlled by the trace minerals and regional geochemical background. The Bauxite is characterized by enriched LREE and the bottom iron weathering crust is with small differential degree of LREE and HREE. The REE distribution plots of bauxite and clay from same deposit are same. The difference of the enrichment degree of rare earth elements come from bauxite and clay in different deposit. The iron oxide-rich layer and aluminum-rich layer get the maximum enrichment of REE, and the characteristics of the enrichment of LREE and HREE. According to the δEu and trace elements diagram, it is indicated that the iron oxide-rich layer are weathered by carbonate rocks, and the bauxite and clay are source from the alumina silicates rocks.Use trend surface analysis to recover the paleo-karst topography in Late Carboniferous. The results show that The development groups of the paleo-karst depressions. Along the strike, the highlands and the depressions appear in turn, and along the dip, they appear in line.The high grade zone of the ore corresponds to the area of the paleo-karst depression. The paleo-karst depression is the enrichment center of high grade ore. In the region, the control zone of the paleo-karst geomorphology is obviously different.