Fe analyses may be reported either as total iron or as explicit ferrous (Fe2+) or ferric (Fe3+) values. Sometimes Fe data must be in a specific format before samples can be displayed on a classification diagram. To make sure that ioGAS uses the correct column values the following aliases are available:
· Fe – Total Fe
· Fe2O3 – Total ferric (3+) oxide
· FeO – Total ferrous (2+) oxide
· Fe2O3* – Explicit ferric (3+) oxide
· FeO* – Explicit ferrous (2+) oxide
Diagrams which require an Fe component in most cases will have a (Total Iron) and an explicit (Fe2+_Fe3+) version to choose from. The (Total Iron) version requires one of Fe, Fe2O3 or FeO to be aliased. The (Fe2+_Fe3+) version requires two Fe columns of data to be aliased to Fe2O3* and FeO* otherwise the calculation or diagram will be greyed out.
It is possible to calculate explicit Fe2+ or Fe3+ values from total Fe values (and vice versa) using a variety of methods, some of which can be found under the Calculations menu. Use these calculations to converted data into the correct Fe format required.