The Bauxite Geological Characteristcs And Genesis In Western Xiaoyi Of Shanxi Province

The Xiaoyi western bauxite district is located the northwest edge of the Huoxi Basin in the centra station of Shanxi. Bauxite exists in the iron aluminum rock section, which is in low of the Carboniferous Benxi formation. The rock section contains the bauxite of G layer and the Shanxi iron. Its section is ferruginous rock, aluminum rock, argillaceous rock from bottom to top, which come into contact with the underlying strata of Ordovician limestone and with the overlying strata of the half ditch segment of Benxi.Orebody shapes are layered, stratoid, lenticular, nodus Nelumbinis Rhizomatis, which is mainly affected by basal paleokarst landform. Natural types of ores are clastic bauxite bauxite, rough shape, bean oolitic bauxite, dense type bauxite. The rough shape of bauxite tastes highest, beans oolitic and clastic bauxite followed by, dense type bauxite worst. Internal microscopic structure of the various types of ore is the different size fractions debris structure, which is mainly sand debris and silt; followed by beans oolitic; occasionally the gel structure, crystallization superfine grain structure and metasomatic relict structure. The ore structures is simple, mainly for the massive structure and honeycomb structure. The various types of ore contained diaspore, kaolinite, pyrophyllite, illite, chlorite, hematite, siderite, pyrite, rutile, zircon ect.Trace elements feature information of B、Sr/Ba ratio、Ga content in Xiaoyi western bauxite four categories ore content displays the Xiaoyi western bauxite should be marine deposit. Four natural types of Xiaoyi western bauxite ore and basal carbonate REE chondritic element distribution curve illustration shows four types of bauxite and base plate carbonate rocks have similar REE distribution curve characteristics, This shows Xiaoyi western bauxite material source is the basal carbonate rocks.The Xiaoyi western bauxite district belongs to sedimentary bauxite deposit, its sedimentary formation process can be roughly divided into two stages:the transgression before and transgression sedimentary mineralization stage. In the first phase, the base carbonate experienced long-term weathering, forming a calcium rich lateritic weathering crust substance and peneplanation palaeokarst landform. This stage, on the one hand provides material basis for the formation of calcium-clay material, on the other hand provides places-karst depression to mineral migrated and emplaced. The second phase of as Benxi seawater inundation advance formation of calcium the lateritic material is migration, and then deposited in a karst depression, the formation of industrial value, bauxite body.Bauxite mineralization, the Xiaoyi west where Horsey basin paleogeographic unit is a karst depression, its northwest side of Lvliang ancient island, east of the Huoshan ancient land, the Lingshi underwater basin uplift turn HuoWest Basin is divided into Fenxi, and Renyi two secondary sedimentary basins formed a closed-semi-enclosed coastal lagoonal depositional environment, Xiaoyi bauxite the Fenxi Basin where the best closed. Benxi group that this ancient geographical background began to deposit, the short sea transgression before Pan karst lake basins in the region sometimes communicate with the sea, sometimes isolated with sea, this sea-land the replacement of the depositional environment control Benxi phase deposition phase distribution.The Xiaoyi western bauxite is a sedimentary origin bauxite bed, the process of deposit formation has four stages of development, carbonate rock and its transition rock weathering crust of mainly long-term weathering process Medieval laterizationstage, the formation of mature red clay/calcium laterite material migration due to surface water effects or flooding role in the formation of karst depression in place redeposition stage, poorly consolidated sediments under the pressure of the overlying sediments and dehydrationcompaction, consolidation diagenetic and deformation, recrystallization of diagenetic and burial metamorphism stage, has formed a bauxite exposed surface to accept again weathered supergene enrichment stage due to crustal movement.