Chapter 1. General information about uranium. 1.2. Propagation in nature

Full text: Uranium is a typical element in the granitic layer and sedimentation shell of Earth crust. The average uranium propagation in Earth crust is (clarke) 2.5•10^-4 % according to the mass, in acid igneous rocks 3.5•10^-4 %, in clays and shales 3.2•10^-4 %, in basic rocks 5•10^-5 %, in ultra-basic rocks of mantle 3•10^-7 %. Uranium energetically migrates in cold, hot, neutral and alkaline waters as both simple and complex ions, especially as carbonated complexes. Oxidation-reduction reactions play an important role in uranium geo-chemistry, since uranium compounds, as a rule, are very soluble in waters with oxidizing medium and poorly soluble in waters with reducing medium (for example, hydrogen sulfide). In the course of geological history, the uranium propagation in the Earth's crust decreased due to radioactive decay; Pb atoms accumulation in the Earth crust relates to this process. Radioactive decay of uranium plays an important role in total Earth crust energy, being an essential source of depth heat. (author)