When magma underneath the mountain cooled and the temperature dropped, the anhydrite began to dissolve.
anhydrite was a relatively abundant, primary phenocryst phase.
Stratigraphic seals are provided by regionally extensive anhydrite and halite strata.
British Dictionary definitions for anhydrite
a colourless or greyish-white mineral, found in sedimentary rocks. It is used in the manufacture of cement, fertilizers, and chemicals. Composition: anhydrous calcium sulphate. Formula: CaSO4. Crystal structure: orthorhombic