Petrographic analysis of a potash evaporite, the Salado Formation (Permian) of New Mexico and Texas, has allowed distinction of primary sedimentary features, from metamorphic alteration "overprints." Primary sedimentary textures in laminated anhydrite, thin-bedded halite, and muddy halite include vertical growth structures (gypsum "swallowtails" and "chevron" halite), incorporative and displacive intrasediment growth of gypsum, halite, and glauberite, carbonate-gypsum and gypsum-halite couplets, and gypsum wave ripples. The Salado primary chemical and depositional environment, interpreted by comparison with similar features from modern evaporite environments, is a salt pan up to halite saturation alternating with a perennial brine body stage at gypsum and sometimes halite saturation.

A complex diagenetic-metamorphic history has imparted a secondary alteration overprint on the Salado salts. Halite has recrystallized; gypsum has dehydrated to anhydrite, reacted with brine to form polyhalite, or dissolved, leaving a void now occupied by halite or sylvite. Formation of new minerals, the most important being sylvite, carnallite, langbeinite, and kieserite, has occurred as displacive or incorporative intrasediment growth (langbeinite), or as void filling cement (sylvite, carnallite). Further alteration is recorded as reaction of brine with langbeinite to form kieserite, kainite, leonite, and bloedite. From their observed distribution, texture, and mineralogy, and by comparison with experimental data, secondary features in the Salado are interpreted to have resulted from the subsurface migration of alien, non-seawater composition brines at elevated temperatures.

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