Original paper

A new method for the adjustment of Fe2O3/FeO ratio in volcanic rocks for the calculation of CIPW norm

El-Hinnawi, Essam


A new method is introduced to adjust the percentages of Fe2 O3 and FeO in volcanic rocks for the calculation of their CIPW norms. The method is based on the linear relationship between total alkalis (Na2 O+K2 O) and the degree of iron oxidation, OXFe (Fe2 O3 /Fe2 O3 +FeO) in subalkalic and alkalic volcanic rock series. The two equations formulated from this relationship pro- vide more flexibility for the calculation of OXFe and, hence, the adjustment of Fe2 O3 and FeO, or the calculation of both oxides if the iron is given as total Fe (either as Fe2 O3 Tot or FeO Tot), prior to the calculation of the CIPW norm.


cipwalkalic seriesbasalt tetrahedronsubalkalic seriesiron oxidation