Trace-element content of ?Karst Bauxites? and their parent rocks in the mediterranean belt

Abstract

This work deals with a concise but comprehensive study of trace-element distribution in the bauxite deposits of Mediterranean belt. Although the alloctonous and mainly detritic characters of several “karst bauxite” deposits are well established, their parent rock has remained largely enigmatic. Evidence is available that some chemical elements, notably Zr, Cr and Ga are largely immobile during the weathering and diagenesis and study of such trace-elements in “karst bauxites” permits to make an approach to the lithological nature of their parent rocks. It is shown, by reference to analyses of bauxites from Mediterranean areas, that all the deposits studied are aligned from a Cr rich pole related to ultramafics to another pole rich in Ga and Zr contents and in genetical relation with acidic parent rocks. The results obtained by this way have been controlled by application of “trace-element accumulation coefficient” which permits to distinguish four principal zones of bauxite derived from the parent rock of different lithological characters (Fig. 3).