Mineral Transformation And Element Migration During The Evolution Of Bauxite In Sanhe Ore Deposit,Western Guangxi

Sanhe bauxite deposite is located in southwest of Western Guangxi, together with the bauxite deposites around Debao and Napo formed the large size bauxite orefield. Western Guangxi is an important place of bauxite origin of China. The bauxite ores in Western Guangxi, China, mainly belong to the karstic type, and can be further divided into two subclasses, the Permian sedimentary and quaternary accumulated bauxites. The Permian bauxite ores were formed by uplifting, breaking-up and weathering, and then accumulated in the karstic depression area at the end. Accumulated bauxite is the main target of current mining for its high quality and easy mining process. In this study, multiple test methods and statistical analysis were used to reveal the evolution of accumulated bauxite in the mineral and element scale.XRD is used together with electron microprobe to obtain mineral composition. It reveals that ore minerals in Sanhe bauxite deposits mainly include diaspore,chamosite, anatase,pyrite and small amount of ilmente, goethite and kaolinite. Minerals in the bauxite are of different shapes. Typically, minerals are highly mixed and symbiosis with each other. Most minerals in the sample have a sign of dissolution due to the supergene condition. Thus, element substitution and interfusion is very common.Geochemical analyses indicate that Al2O3, Si O2, Fe2O3, Fe O, Ti O2, Mg O and H2O+ are the main components of the bauxite ores. Other components are less than 1%, indicates a high maturity. The content of Cr and Zr is high, with an average content of 867.93×10-6 and 792.16×10-6. In addition, the content of Li, Ba, F, Nb, S, Sr, Zn and V is relatively high(average content 100×10-6 ~40 × 10-6). element such as Cs,Cu, Ga, Hf, Ni, Sc, Th and U have an average content of 10×10-6~100×10-6. Bauxite has a very high ΣREE and an enrichment of LREE.In the process of evolution, bauxite was first effect by the leaching from surface water. At the time, the ores were mostly in a reducing environment and minerals close to the fracture were tend to be weathered fist. Mineral dissolution holes were formed during this stage of process and element substitution occurred. As the oxidation developed into the ores, chamosite, which is the main concentrator of Al、Si、Fe、Mg and Fe2+, were dissolved significantly. During this stage of process, Fe2+ was oxidized to Fe3+ and formed the mineral aggregate of goethite and hematite. That is why the ores showing a red-brown color. Diaspore is stable during the weathering and the Al hosted in it was nearly moved. Therefore, Al is relatively enriched in the bauxite.The mobility of the trace elements in bauxite is mainly controlled by the host minerals. Cr and Ti have a relatively correlated change during the process of bauxite evolution, and the explanation is they are both host within the same mineral most likely the anatase. The change of Ce during the evolution of bauxite is quite different from other rare earth elements. This probably indicates REE mineral s present in ores and the migration of Ce is highly related to the dissolution and crystallization of the REE mineral. The content LREE is high in bauxite, but in the process of strong weathering, HREE have a relative enrich trend in bauxite.