NEW AND REVISED DATA FOR SOLID-SOLUTION EQUILIBRIA OF THE QUINARY SYSTEM NA2CL2-K2CL2-MGCL2-NA2SO4-K2SO4-MGSO4-H2O

The data for solid-solution equilibria of the system Na2Cl2-K2Cl2-MgCl 2-Na2SO4-K2SO4-MgSO4-H2O are a necessary requirement for any geochemic al modelling of the primary formation of marine evaporites and their s ubsequent diagenetic and metamorphic alteration. After the pioneer wor k by van't Hoff (1912) a first comprehensive compilation of solubiliti es of salt minerals was published by D'Ans (1933) updated by Autenriet h (1955). Today it appears that there are 11 new invariant points with in 2 degrees to 108 degrees C at saturation with respect to halite. Ou t of the former points 13 have been discarded, and revised data are gi ven for the points still valid. Moreover, solubility data for 6 isothe rmal sections of the above system and its bounding systems at halite-s aturation have been summarized. Some numerical examples, comprising on e of the new points, show in how far current geochemical models are af fected by the revised data.