Geochemistry and Mineralization of the Permian Bauxites with Contrast Bedrocks in Northern Guizhou, South China

A succession of Permian bauxite deposits are concentrated in Wuchuan, Zheng’an and Daozhen counties of northern Guizhou, South China. These deposits overlie contrast bedrocks, which are discriminated from the other bauxites of karst type in South China. Horizons of these bauxites are typified by sandwiched constructure, the upper and the lower layers of bauxitic claystone interbedded by the ore layer, and by abundant pyrite occurring in the ore and the lower layers. A geochemical study was carried out on samples from two boreholes of bauxitic profiles with claystone and carbonate bedrocks, respectively. It shows that the diverse profiles illustrate contrast mobility of elements. The profile overlying clayey bedrock is depleted in most elements including REE but variously enriched in HFSE, Pb, Mo, and half mass of Al 2 O 3 was leached out; the profile overlying carbonatic bedrock is highly enriched in REE and moderately in HFSE and Pb, its Al 2 O 3 mass was basically preserved. Both horizons are extremely enriched in alkali of Li and variously in Ce. A new genetic model is suggested accordingly. Tropic climate, coastal plain and frequent transgression and regression during the Permian caused a transition of weathering profiles from laterization to bauxitization in northern Guizhou. Massive pyrite in the horizons formed under reducing environment during the transgression through combining of iron enriched in the laterite profile and sulfur from the soaking and penetrating seawater; during the regression, oxidation of pyrite caused strong acid medium and induced the bauxitization.