NATURAL NUCLEAR REACTIONS AND THEIR INFLUENCE ON THE ISOTOPIC COMPOSITION OF THE CORRESPONDING ELEMENTS

Changes in the isotopic composition of chemical elements, which include natural radioactive (mother) and radiogenic (daughter) isotopes, are characterized. It is shown that the ²³⁸U/²³⁵U isotopic ratio increased from 3.117 at the age of 4567 million years to 137.88 at the present time. The isotopic composition of lead directly depends on the ratio between the content of uranium (thorium) and lead (μ and W, respectively), which have significant variations in different reservoirs. In connection with the geochemical properties of Sm and Nd and similar to them Lu and Hf, and opposite to them Rb and Sr, in the process of formation of the earth's crust, their differentiation occurs and the isotopic composition of Nd, Hf and Sr in the earth's crust and mantle changes with different rate, due to which isotopic ratios of ¹⁴³Nd/¹⁴⁴Nd, ¹⁷⁶Hf/¹⁷⁷Hf and ⁸⁷Sr/⁸⁶Sr are used to identify the source of igneous rocks.