The Dicker Willem carbonatite complex intrudes Precambrian basement of the Namaqualand Metamorphic Complex. The main intrusion is composite, characterized by dismembered remnants of an ijolite-syenite suite enclosed within a circular sövite plug. Sövites, including magnetite, aegirine, biotite, apatite apd pyrochlore-bearing varieties and their associated cumulates have been disrupted by intrusion of a concentric suite of alvikite cone sheets and ring dykes. Alvikites range from microsövite-dominated varieties at the outer margin to dolomite-phyric types near the centre of the intrusion. Dykes of ferro-alvikite intrude the cone sheet sequence. Steep-sided, funnel-shaped pipes of carbonatite breccia intrude the central complex and are the source of ubiquitous dykes of microbreccia-tuffisite, yellow carbonatite and veins of calcite. Gneisses are patchily reconstituted to potassic fenites during sövite intrusion and are subsequently intruded by dykes, cone sheets and plugs of carbonatite, trachyte and their breccia equivalents. Intense brecciation, faulting and updoming of the gneisses and trachytes accompanied intrusion of the alvikites. Chilled margins and spinifex quench textures in alvikites, and open-space infilling of fractures formed during breccia pipe emplacement indicate a high level of intrusion. Dicker Willem is interpreted as a diatreme-like, subvolcanic carbonatite from which the uppermost effusive products have been removed by erosion.