Mineral features and genesis of bauxite deposits in central and southern Shanxi Province

The mineral features of bauxite in central and southern Shanxi Province were studied by polarization microscope, X-ray diffraction (XRD), infrared spectroscopy (IR), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Experimental results show that the major minerals in bauxite are diaspore and kaolinite, with a few of illite, chlorite, hematite, goethite, anatase, rutile, quartz, flint, potassium feldspar and calcite. Diaspore is divided into three tyes:cryptocrytal-microcrystal, allotriomorphic granular and short columnar crystal with a lower endothermal temperature, and a=0.441 546 nm, b=0.945 445 nm, c=0.285 250 nm, mainly formed by desiliconization of kaolinite, a little was transformed from crystallization. Kaolinite was formed during the weathering process in warm and humid climate and a part of kaolinite was the porduct of silica replacement Anatase was formed in low temperature and low pressure environments with abundant TiO₂ supply. Hematite came from dehydration of hydrous ferric oxide mineral, small part from early metallogenic swamp facies or marine deposit; Quartz, potash feldspar and some other heavy minerals are the terrigenous clastic.