Rare earth elements and nickel in the Grebnik diasporic bauxite deposit, Metohija (Kosovo)

The karstic bauxites of Mt. Grebnik, Kosovo, represent a unique deposit of the diasporic bauxites of Upper Cretaceous age in the former Yugoslavia. They are typically transitional between ferruginous bauxites and karstic Ni-Fe ores. Bauxites originated from surrounding Cretaceous weathering crusts on ultramafic rocks and on shale of the diabase-chert formation. Chemical and trace element analyses of the bauxite samples collected along a vertical profile of a typical deposit are presented and discussed. Trace element patterns, including REE and Ni, are typical for karstic bauxites formed in situ, during bauxitization of argillaceous material accumulated in a karstic depression. In connection with this, a progressive enrichment of the REE and Ni toward the bottom of the deposit is well pronounced, with formation of authigenic REE mineral, synchysite-(Nd), and Ni-bearing chlorite on the contact with the footwall limestone.