GEOCHEMISTRY OF ISOTOPES

The isotopic composition of the earth's crust is never static, due to various radioactive processes. This is especially noticeable on geologic time scales. The isotopic exchange reactions, particularly those involving lighter atoms, are intensive in the outer shell of the earth, notably in the biosphere. The biospheric exchange reactions are primarily responsible for local enrichments and anomalous absences of various isotopes, especially those of oxygen, carbon, sulfur, and hydrogen. Isotope geochemistry is a tool which will help solve problems of past major and minor geologic events in the genesis of rocks and minerals. It is hoped that isotope geochemistry will introduce two new parameters into geologic investigation of time and temperature of natural processes. --G. E. Denegar.