An assessment of the ThHfTa diagram as a discriminant for tectonomagmatic classifications and in the detection of crustal contamination of magmas

The ThHfTa diagram, recently proposed [1] as a means of discriminating basalts erupted in various tectonic environments and of detecting crustal contamination in such magmas, is shown to be unsatisfactory for both of its stated purposes. Data are presented for Th, Hf, Ta, Sr and Sr- and Pb-isotopes in basic lavas and a dolerite sill from the ensialic British Tertiary Volcanic Province (BTVP). Taken in conjunction with published results, the …