Isotope geochemistry

Object of investigation

The isotope geochemistry is the study of the distribution, fractionation and radioactive decay of the isotopes on Earth and in space. It is a portion of the geochemistry and is divided into two branches:

• The stable isotope geochemistry deals with isotopes that do not decay. Most chemical elements have multiple isotopes. For chemical and biological processes behave this partly different ( isotopic fractionation ). Thus the ratio of different isotopes of the same element between different substances ( minerals, water, organic substances ) is different. This allows isotope ratios conclusions about the evolution of such Geomaterials to. Important are the stable isotopes of hydrogen, oxygen, the carbon, sulfur, calcium, silicon, strontium and iron.

• The geochronology determined the launch or metamorphic age of minerals, rocks and water. It makes use of the fact that radioactive isotopes decay with time. As long as the atoms or isotopes between a geological object (such as a mineral ) and its surroundings can be exchanged, a radioactive isotope x and y before a stable isotope in a so-called " initial isotope ratio " to each other. This is determined by the rate of formation of the radioactive isotope by nuclear fusion in the sun or other stars on the one hand and its decay constant on the other hand, may vary over geological time. Once the exchange is inhibited because the temperature drops to the extent that no significant diffusion occurs any more, the geochronological clock starts ticking. One speaks of a " closure temperature". The information presented in the mineral radioactive isotopes decay and there is no supply of new radioactive isotopes more instead. So that the concentration of a radioactive isotope to a stable isotope is a measure of the age of the mineral, which is measured from the time at which the temperature zone was last below. Important methods of dating are the uranium - lead dating, potassium - argon dating, the argon - argon method, the rhenium - osmium method and the radiocarbon dating method.

Methods of investigation

The concentration of the isotope is measured using the mass spectrometry.