Major element geochemistry of silcrete from a portion of inland Australia

Silcrete is exceedingly uniform in composition, revealing no consistent variations across a large portion of the Australian interior. Analyses of host quartzose sediments suggest that a small increase in Si content, associated with a reduction in Al and H₂O, accompanied silcrete formation. Depletion of Fe, Mg, Ca, K and P point to intense leaching in a near-surface environment. Concentration of Ti during silicification is confirmed and attributed to accumulation from within the host sediments. Analyses of porcellanites derived from silicification of kaolinized claystones reflect considerable Si concentration, along with marked depletion of Al and other, more mobile elements. Reducing conditions under a wet climatic regime are postulated during the early phase of silcrete formation. Subsequent climatic change to aridity favoured silcrete development and preservation.