Numerous Sn- and Nb-Ta-rich pegmatite bodies are present in a NE-trending, approximately 20 km wide zone, consisting of schistose Damara metasediments and granites, in the area between Cape Cross and Uis. Structural analysis led to the recognition of the Cape Cross - Uis pegmatite field as a graben structure. Emplacement of stanniferous pegmatite bodies was structurally controlled by graben-related, en echelon Riedel-fractures. Three major pegmatite swarms, Uis, Strathmore and Karlowa, are located in clearly defined N-S trending, fracture-bounded zones. Significant Sn, Nb and Ta mineralization occurs in replacement units showing intensive albitization and greisenization. Detailed mapping and structural analysis suggests a younger age than previously postulated for the mineralized pegmatites. A possible Jurassic - Cretaceous age of mineralization is discussed.