Primary mineralization in Nigerian ring complexes and its economic significance

Abstract

The Younger Granite ring complexes of northern Nigeria are the major source of tin and columbite mined in Nigeria. The minerals are derived from placers which originated by weathering of primary sources. The search for tungsten and tin over the past fifty years has exhausted most of the placer deposits necessitating closer study of the primary sources. Reassessment of former workings and especially the results of underground exploration and diamond drilling have enabled the classification of primary mineralization bodies into two basic genetic types. In the first type are disseminations of cassiterite in biotite granite or cassiterite + columbite + other minerals in various combinations. The second type is vein-controlled hydrothermal mineralization which is further classified according to structural, textural and mineralogical features. The hydrothermal mineralization includes greisens and fissure-filling veins. Depending on the mineral assemblages the second type can be divided into quartz-sulphide-cassiterite and quartz-cassiterite-wolframite veins.