Abstract:

The Southern Central Zone of the Damara Orogen in Namibia is one of the world’s most important alaskite-type uranium ore clusters, hosting super-large uranium deposits such as Rössing and Husab. Major exploration breakthroughs have been achieved in this region in recent years. This paper systematically reviews the regional geological setting and geological characteristics of alaskite-type uranium deposits, and takes the “source-transport-trap-modification-preservation” metallogenic process as the main framework to analyze key aspects including ore-forming material sources, magmatic origin and evolution, tectonic-magmatic coupling mineralization, and post-ore modification. The results show that alaskites can be classified into six types (A-F), of which only D- and E-types are mineralized. Barren alaskites originated from muscovite dehydration melting during the syn-collisional stage, whereas mineralized alaskites originated from biotite dehydration melting during the latecollisional stage. Biotite melting introduced F^- into the magma, forming UF_m ^4-m complexes that enabled uranium transport in the  melt, representing the key mechanism for the formation of ore-forming magma. During fractional crystallization, biotite separation removed Nb from the residual melt, serving as an important factor in controlling uraninite-type versus betafite-type mineralization. The D4 tectonic regime transformation triggered uranium mineralization. The Khan River Lineament as the conduit, dome margins and marble contacts as the emplacement sites of alaskite bodies, together with Mesozoic hydrothermal superimposition and Cenozoic supergene leaching, constitute a complete mineralization-modification-preservation process. The comprehensive information prediction method based on metallogenic theory delineated 14 prospective targets within the Rössing mining license, with a predicted resource potential of approximately 140,000 tons of uranium. The A1 (Z17-19) target has been confirmed through drilling as a very large uranium deposit, achieving a major exploration breakthrough. 

Key words: magmatic evolution, tectonic regime transformation, alaskite-type uranium deposit, four-stage metallogenic model;
R?ssing area, Namibia