Geochemical characteristics and ore-forming materials of bauxite deposits in southeast Yunnan Province

Abstract: There exist abundant bauxite resources in southeastern Yunnan Province. Taking sedimentary bauxite deposits in southeastern Yunnan Province as the research objects, the authors studied their geochemical characteristics and discussed their ore-forming material sources. These deposits are enriched in rare earth elements， dispersed elements gallium，ferrous metal element Ti and rare metal element Nb in aluminum-containing rocks, with the reserves attaining the requirements of industrial exploitation. In aluminum-containing rocks, there are generally high REE values and big differences between samples, with the characteristics of moderate Eu negative anomaly, complex Ce anomalies composed of poaitive and negative anomalies. REE distribution patterns for normalized aluminum-containing rocks exhibit rightly-oblique curve with weak “V” shape and different slopes, reflecting varying degrees of REE fractionation. REE characteristics are similar to features of underlying limestone of Weining Formation, which shows that there exists a close relationship between aluminum-containing rocks and limestones of Weining Formation. Aluminum-containing rocks are enriched in LILE elements Li, U, high field strength elements Nb, Ta, Zr, Hf, Th, transition elements V, Cr, Ti, and dispersed elements Ga, with the obvious depletion of the remaining elements. The authors found that aluminum-containing rocks deposited directly in the weathering crust. Aluminum-containing rocks have complex Ce anomalies and moderate Th/U (3-7), high Sr/Ba (> 1) and high Al2O3/TiO2 (3.41-44.02), suggesting that main ore-forming materials of sedimentary bauxite deposits were derived form the weathering crust of limestones of Weining Formation, and sedimentation played the role of the reformation of the ore-forming materials of the weathering crust.