Geochemistry of Proterozoic granulites from northern Prince Charles Mountains, East Antarctica

Abstract

The late Proterozoic basement of the Porthos Range northern Prince Charles Mountains, east Antarctica, is dominated by a suite of felsic to mafic granulites derived from igneous and, less importantly, sedimentary protoliths. Compositionally, they are broadly similar to granulites occurring along the Mac. Robertson Land coast and southern Prince Charles Mountains. Ultramafic to mafic orthopyroxene' + clinopyroxene granulites with relict igneous layering occur as lenses within the felsic to mafic granulites, and show compositional evidence of a cumulate origin. The felsic to mafic granulites are intruded by several large charnockite bodies that have similarities to the Mawson Charnockite, and may have formed via a two-stage partial melting process. The charnockite and host granulites are chemically very similar, and both may have been derived from a common middle to lower crustal source region. Undepleted K/Rb ratios suggest retention of original chemistry, with variations being due to fractionation processes. Normalized trace element patterns resembling modern-day arc settings suggest that the Porthos Range granulites were possibly generated in a subduction zone environment.