The stratigraphy at the Gamigab Sn prospect consists of two mainly schistose units separated by a thick marble unit which have been correlated with the Orusewa Formation, the Karibib Formation and the Kuiseb Formation respectively. Four phases of folding affected the lithologies with the south-south-west trending F2 folds defining the main structures in the region. The grade of metamorphism is in upper greenschist facies and to the south-east and west the effects of contact metamorphism are seen in the form of cordierite pseudomorphs and biotite spots. Cassiterite is hosted within east-west trending quartz veins that cross-cut previously altered country rocks. Hydraulic brecciation is spatially associated with the mineralization and alteration. These breccias occur in antiformal structures within the marble and developed in response to a sudden pressure release due to a build up of fluids at the contact between the Orusewa and Karibib Formations. Two Karoo-age intrusions penetrated the metasediments north of the mineralization. One is a ferruginized porphyry plug and the other is an altered dolerite plug. It is possible that the same hydrothermal system was responsible for the alteration of the intrusions, the brecciation and the alteration-mineralization, indicating a possible Karoo-age for the hydrothermal activity.