Rickwood P.C. Boundary lines within petrologic diagrams which use oxides of major and minor elements

Lithos, vol. 22, Amsterdam, 1989, p. 247-263Use of some petrologic diagrams applied to analyses of volcanic rocks is unnecessarily difficult due to
lack of data for construction of discriminant lines between rock series. Coordinates are provided for sufficient points to enable accurate plotting of the boundary lines within seven diagrams, viz.: (1) TAS - total alkalies (Na2O+K2O) vs. SiO2; (2) K2O vs. SiO2; (3) AFM; (4) Jensen; (5) KTP K2O - TiO2-P205; (6) FMS - (FeO*/MgO) vs. SiO2; and (7) TAKTIP- K2O/(Na2O+K2O) vs. TiO2/P2O
5. Different versions of these boundaries are collated to indicate their variable position, and it is demonstrated that inter-laboratory analytical precision suffices to account for almost all of their spread on the TAS and K2O vs. SiO2 diagrams.