In the hills west of Somerset Dam, a gabbro-red rock complex is emplaced in the Lower Triassic Neara Volcanics. The gabbroic portion is plug-like, and is mainly olivine gabbro with a horizon of banded troctolite. The upper part is quartz gabbro, with micropegmatite in the topmost portion.
The red rock is not a direct differentiate of the gabbro exposed. The main part at least, is magmatic in origin and was emplaced slightly later than the gabbro. It consists of quartz and perthite, often intergrown, with iron ore a common accessory.
The metamorphic effects due to these two rock types are compared and contrasted.
Quartz diorite and felsite dykes around the gabbro and red rock are thought to be part of the complex.