Geochemical mass-balance and oxygen-isotope constraints on silcrete formation and its paleoclimatic implications in southern Australia

Abstract

ABSTRACT: Two geographically distinct silcrete associations are pres-ent in southern Australia, inland and eastern; these were sampled in central South Australia and central Victoria, respectively. At each site, both silicified and immediately adjacent unsilicified parent material were collected. Analytical data from these pairs were used to construct isocons, assuming Zr immobility, and to calculate the volume change and amount of silica introduced during silicification. These results, to-gether with whole-rock oxygen-isotope compositions, were used to de-termine the d18O of the introduced silica. The results show that the eastern silcretes in central Victoria are probably linked genetically to the associated basalts, weathering of which supplied the introduced silica. This conclusion is based on the close spatial connection between the two, as well as the substantial amount of introduced silica in the silcretes (greater than in the inland silcretes), resulting in volume increases in some eastern silcretes. Ox

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Last time updated on 12/04/2017

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