Variations in light stable isotope ratios (such as hydrogen, carbon, nitrogen, oxygen, sulphur, chlorine and bromine) are caused by processes that are called isotope fractionation. Fractionation is caused by differences in physical or chemical processes that are mostly caused by the difference in weight of the isotopes. Variations in the isotope composition of an element can also have its origin from radioactive decay of mother isotopes which may be present in different quantities in the original environment. In this case we call these daughter isotopes radiogenic. The isotope geochemistry of strontium is a good example of an element where isotope variations are mainly caused by radioactive decay of a mother isotope, in this case that of β-decay of 87Rb to stable 87Sr. Chlorine and bromine do not have any radiogenic isotopes and all isotope variations found for chlorine and bromine are caused by fractionation processes on these isotopes.
- Czarnacki M, Hałas S (2012) Isotope fractionation in aqua-gas systems: Cl2-HCl-Cl-, Br2-HBr-Br- and H2S-S2-. Isot Environ Health Stud 48:55–64Google Scholar
- Hoefs J (2009) Stable isotope geochemistry, 6th edn. Springer, BerlinGoogle Scholar
- Melander L (1960) Isotope effects on reaction rates. Ronald, New YorkGoogle Scholar