Application II Stable Isotope Geothermometry

Although the scope of this book does not allow an appropriate treatment of stable isotope compositions of earth s materials (excellent monographs on this subject can be found in the literature—e.g., Hoefs, 1980 Faure, 1986), we must nevertheless introduce the significance of the various compositional parameters adopted in the literature before presenting the principles behind stable isotope geothermometry. 

Let us consider again a generic isotopic exchange as represented by a reaction of the type 

The fractionation factor a represents the relative distribution of heavy and light isotopes in the two phases at equihbrium (somewhat similar to the normalized distribution coefficient adopted in trace element geochemistry cf section 10.8)  

Assuming the same notation adopted in equation 11.123, we have 

Because the modifications affecting the stable isotope compositions of natural materials are rather limited (and mainly attributable to the processes discussed in sections 11.6.1 to 11.6.3), they are usually expressed in terms of A per-mil variations  

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