The large ring-shaped Mt. Brukkaros is formed by a dome of lower Paleozoic Nama sediments. In the center of the dome a depression 1.5miles in diameter is underlain and surrounded by fine-grained, layered, clastic rocks (microbreccias) derived from brecciation of the Nama sediments and shales. In the surrounding country rocks, 45 satellite vents and numerous radial dikes occur; they are filled with coarse breccias in a carbonate-rich matrix. This structure is the result of phreatic eruptions of a volatile-rich alkaline ultrabasic intrusion meeting water-soaked sediments. The Brukkaros complex is interpreted as a carbonatite volcano in an incipient stage.