Afm Diagram Geology. Commonly used chemographic projections include acf akf and afm example shown here diagrams. Besides sio 2 the five most abundant oxides found in metamorphic rocks are al 2 o 3 cao feo mgo and k 2 o.
Choose p t dialogue box. The afm diagram and p t information is made by constructing petrogenetic grids for the chemical system of interest. To calculate the plotting parameters for the afm diagram the following formulae are used.
For details about these and other ways to project mineral compositions see standard text or some of the references listed below.
Also highly recommended is steve nelson s triangular plots in metamorphic petrology. The three components plotted on afm diagrams are derived from a tetragonal diagram with species al2o3 k2o feo and mgo and are ideal for showing mineral assemblage variations as a function of the composition of pelites. Afm diagram showing the relative proportions of the oxides of alkalis a iron f and magnesium m with arrows showing the compositional change path of the magmas in the tholeiitic and the calc alkaline magma series bt tholeiitic basalt fb ferro basalt abt tholeiitic basaltic andesite at tholeiitic andesite d dacite r rhyolite b basalt ab basaltic andesite a andesite. After irvine and baragar 1971.
