Application of lithogeochemistry to identify stratigraphic units and provenance of the Kanmantoo Group, Kangaroo Island

Abstract

Geochemical data, including Nd isotope ratios, were used to help establish stratigraphic correlations between Kanmantoo Group sedimentary rocks on the mainland and Kangaroo Island, as well as constrain their provenance. Whole-rock geochemistry of the Kangaroo Island and mainland Kanmantoo Group varied, with little consistency, suggesting a mixed sediment source. The Talisker Formation however has a distinctly higher abundance of mafic detritus compared to other Kanmantoo Group formations. Initial Nd data from the Kangaroo Island Kanmantoo Group is between -12 to -15, compared to those from the mainland which range between -9 and -12 (Turner et al. 1993). The Nd data are similar to basement of the Gawler Craton and east Antarctica (Prydz Bay), which are two possible source terrains for the sediments. Palaeocurrent data on Kangaroo Island indicate a southern provenance. The Nd values of Prydz Bay charnockites and felsic gneisses at around 500 Ma are similar to that of the Kangaroo Island Kanmantoo Group. Results from the outcomes of this study suggest that the Kanmantoo Group was derived from a mixture of sources, including the Gawler Craton, west Antarctica (Ross Orogeny) and Adelaidean rocks. However, there appears to be a dominance of sediment from the east-Gondwana Orogenic belt in east Antarctica.