Berthierine-Rich Bauxites in the Kursk Magnetic Anomaly (KMA)

Studying with precision methods the mineral composition of bauxites in the Kursk Magnetic Anomaly (KMA) made it possible to reevaluate the conditions of their formation. Occurring among Early Proterozoic jaspilites in the Belgorod ore region, they are confined to the upper part of the Early Carboniferous lateritic weathering profile on the biotite–muscovite schists. The northern part of the region is dominated by the pseudopisolitic gibbsite ores; the southern part, by the boehmite varieties with an inherited layered structure of parent rocks. Along with aluminum hydroxides, berthierine is a rock-forming (major) mineral in these bauxites. Previously, berthierine was attributed to the subsequent transformation of bauxites. Our data suggest the existence of two berthierine generations. The first generation represents a natural intermediate mineral related to the formation of bauxites during Fe concentration in the weathered rocks. Therefore, we can substantiate a certain stage in the evolution of bauxite formation in the Earth’s history leading to the formation of Paleozoic deposits.