Etanano is a circular complex 2 km in diameter made up from four intrusions of nepheline syenite and one of sodalite syenite. The oldest rock is a central plug of porphyritic nepheline syenite around which are ring-dykes of white, grey and coarse-grained nepheline syenite. The coarse-grained nepheline syenite lies adjacent to the inner ring, xenoliths of which it carries, and has a marked flow texture of aligned feldspar phenocrysts. The sodalite syenite occurs as rounded xenoliths with sharp contacts which are concentrated in two radiating elongate areas within the grey and white nepheline syenite. The principal mafic mineral is aegirine-augite. The youngest rocks are a series of radiating nepheline syenite dykes. There are nine whole rock analyses in Prins (1981) and a further two rock analyses and O isotope data in Harris (1995).