STUDIES ON FORMS OF URANIUM AND ITS DISTRIBUTION IN URANIFEROUS GRANITES

Recently many researchers are inclined to consider that uraniferous granite, as an uranium source, is related to uranium mineralization. It is necessary, therefore, to study the forms of uranium and its mobilization in uraniferous granites.Uranium in granite can be genetically devided into two groups: primary uranium and regenerated uranium.Primary uranium includes: a) uranium minerals; b) uraniferous minerals; c) submicroscopic uraniferous particles in host minerals; d) scattered uranium atoms captured in host minerals. Regenerated uranium includes: a) uranium absorbed on altered minerals; b) interstitial uranium; c) fissure filling uranium; d) dissolved uranium contained in secondary fluid inclusions. The regeneraten uranium consists of uranyl complexes, araniferous ions and/or the particles of uranium blacks and pitchblende.Uraninite is easily soluble under various hydrothermal alteration and on weathering, while other uraniferous accessory minerals are generally much more stable, but still could be mobilized and turned into the generated form of uranium.The analyses of fission tracks, neutron activation, and the semi-quantitative analysis of accessory minerals have been employed to determine the distribution of uranium in granite. Data obtained show that uraninite usually accounts for 40—60％ or even more percent of whole rock uranium in the uraniferous granites. The results indicate that the stronger the alteration of the rocks, the lower the quantity of uraninite and the higher the interstitial and fracture uranium.An example is given to show the application of uranium partition research to the interepretation of uranium source.