Metallogenic Model And Exploration Techniques Of The Bauxite, Western Guangxi, China

There are abundant bauxite resources in western Guangxi, the orebodies can be categorized into accumulation, sedimentary and residual types. The Quaternary accumulation type bauxite is characterized by large reserve, shallow orebody and good ore quality. Conducting the research on the deposit genesis and exploration technique of accumulation type bauxite is significant for innovating the theory of bauxite genesis, large-scale exploration and development of Guangxi bauxite and the substantial increase of domestic bauxite reserve.The spatial structure and evolutionary process of accumulation process have been studied. The area-perimeter model is utilized to quantitatively describe the irregular shape of ore bodies. It is proposed that“viscosity fingering”is one of the main mechanics of the orebodies growth. It is suggested that the changes of oxidation-reduction condition, determined by orebody elevation, is the crucial factor dominating the ore chemical contents and orebody physical parameters. In the higher places, where the orebody is situated in an oxidized situation, the ores have greater Fe₂O₃ content and lower SiO₂ content, also tends to develop a higher ore-bearing rate and more homogenous vertical orebody structure.Using a variety of modern testing methods, accurately determining the mineral compositions of both sedimentary and accumulation bauxite ores are identified. The morphology, chemical compositions, thermal decomposition features and genesis of the major minerals, including diaspore, chamosite, hematite and anatase, are clarified. The independent REE minerals, parisite and churchite, are discovered in bauxite ores, It is shown that, in the transformation process from sedimentary bauxite to accumulation bauxite, a great number of chamosite dissolved, and abundant gibbsite, hematite, goethite, limonite, kaolinite, illite and pyrophyllite formed. The chemical compositions and the elemental occurrence, spatial distribution and mutual relationship are also investigated.Based on conventional LogNi-LogCr diagram, Cr-Ga-Zr triangular diagram and Eu/Eu*-TiO₂/Al₂O₃ diagram, as well as U-Pb and Lu-Hf isotopes of detrital zircons in the bauxite ores, the source rocks are discussed. This study verified that the plume-induced uplift exposed carbonates, as well as the mafic and felsic rocks generated by the Emeishan plume to long periods of intense weathering under humid tropical conditions. The weathering remnants of the high-alumina magmatic rocks and carbonates were deposited on, or transported to, the paleokarst surface and converted to bauxites. On the basis of the metallogenic features and controlling factors, a metallogenic model of bauxite in western Guangxi is established. It is proposed the Permian bauxite is a complex products formed via karstification and laterization. The Quaternary ore compositions are constraint by both Permian reduced and Quaternary oxidized conditions situated in the phreatic and vadose environments respectively.Based on the metallogenic features and long-term exploration experience, this study completes and establishes a system of technology and methods for bauxite exploration. This system adopted a series of new techniques and methods, such as digital technology, GIS technology, quartering weight sampling method in a well, ore washablity and solubility test technology, analysis technology on the Al₂O₃ content in gibbsite.