GEOCHEMISTRY OF THE BLEACHED PROFILES OF THE TERTIARY REGOLITH OF INLAND AUSTRALIA

Kaolinite, alunite, gypsum and opal occur together in the deep bleache d profiles developed on the Tertiary paleosurface of inland Australia. This mineralogical association was thought to result from two success ive weathering stages, the first one under humid, the second under a d ry climate. Modelling of the alteration of shares containing pyrite by a sulfate-rich brine, allows us to ascribe this mineralogical associa tion to a single weathering process under a dry climate.