[en] Two types of uranium mineralization have been found in Jurassic continental sediments of the Madaba area in the Luwegu-Mbarangandu Karroo basin of Tanzania: a peneconcordant, lithostratigraphically controlled type and a discordant type of supergene origin. The supergene uranium mineralization occurs at the base of the lateritic weathering profile at the contact between mottled zone and pallid zone. A typical zoning of the supergene mineralization from Se-bearing Fe-Mn-hydroxides/oxides to uranyl-vanadates to Ni-Cr-rich nontronite indicates that the hexavalent uranium minerals were precipitated at pH changes within the laterite profile. From comparison of the laterite profile of the Madaba area with nickel laterite profiles, it is concluded that the Madaba laterite developed under tropical wet-dry, oversaturated conditions. The lateritization process was probably initiated by a Miocene climatic change and may continue locally up to the present. A genetic model for the supergene uranium mineralization is presented. It is assumed that uranium was remobilized from the primary, peneconcordant mineralization during the lateritic weathering process and redeposited at local permeability barriers by pH changes. Limited alpha-spectrometric data indicate that the active uranium remobilization and redeposition continued during the last 1 Ma. (author)