Early Precambrian metavolcanic and metasedimentary rocks of the Schreiber-White River greenstone terrain have been intruded by rocks of the Coldwell alkaline complex. A thermal metamorphic aureole produced by the complex attains pyroxene hornfels facies in adjacent country rocks.
The earliest magmatism, center 1, is exposed at the western margin of the complex and consists of gabbro and ferroaugite syenite. Younger, center 2, silica-undersaturated syenites intrude both the gabbro and ferroaugite syenite.
The gabbro is characterized by igneous layering and evidence of deformation, in the form of cataclasis and recrystallization of the feldspar. Ferroaugite syenite intrudes the gabbro and contains inclusions of an ilmeno-magnetite bearing cumulate rock and country rock xenoliths.
The principal rock units are crosscut by a dyke suite exhibiting a complex intrusive history. The most common dyke type is lamprophyre.