Late Palaeozoic and Early Mesozoic rocks of the Parmeener Super-Group are subdivided on a strict lithostratigraphical basis, and not in the time terms 'Permian' and 'Triassic'.

Pegmatoids in a Late Oligocene olivine nephelinite plug near Round Lagoon form a complex low-pressure fractionation suite. The host nephelinite contains meta-peridotite and meta-wehrlite mantle xenoliths and its composition (Mg# 0.63) may refl ect both mantle and then limited low-pressure fractionation. The pegmatoids range from u!tramafic through mafi c ro feldspathic assemblages in a progressive, but discontinuous, fractionation sequence (wehrlite->-olivine clinopyroxenite->-sodalite ijolite, ijolite, nepheline syenite-;, alkali syenite). Within this sequence, olivine and clinopyroxene compositions decrease in Mg content, while clinopyroxene becomes increasingly Na-and Fe-rich to produce late stage aegirine-augite and aegirine. Nepheline is prominent in the sequence and crystallised over a wide temperature range from 1000° to <500°C. The presence of sodalite suggests volatile Cl-rich fl uxing. Mg-rich spine! crystallised in early assemblages, distinct from Fe-and Ti-rich oxides of the magnetite-ulvospinel series in later assemblages. The Round Lagoon low-pressure pegmatoids developed by fractionation in a narrow, vertical feeder rather than in broad lava ponds such as those noted in nephelinite Rows at Inverell,