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The studied evaporites are situated in SE of Tehran and include different Tertiary units. These evaporite sequences are the oldest units in the area with upper Eocene to lower Oligocene age which contain rock salt, gypsum, carbonate, shale, marl and some alkali volcanic intrusions. Field and petrographic studies have been employed to unravel depositional setting, diagenetic history and potash-bearing horizons of these sequences.
Petrographic examinations indicating that primary mineral have been crystallized on the basin floor and then subjected to the syndepositional early diagenetic back-reaction processes. Progressive evaporite deposition and neoteric water influxes to the basin motivated chemical variations in brine composition, which in turn, induced back-reaction processes. Finally, these evaporite deposits buried to the shallow depths.
Petrographic studies and mineral assemblages suggest a marine origin for brines in this evaporitic basin. However, possible influx of volcanogenic emissions into the basin should not be ignored.
The worldwide sea-level fluctuations during Pyrenean orogeny gave rise to distinct regressions in the North Central Iran in the Eocene-Oligocene time and in some regions shaped shallow marginal marine extensional basins associated with continental basalt. Some of these basins, such as studied area, were sites of extensive marine evaporite deposition. Gradual syndepositional subsidence, along with evaporite deposition and intermittent seawater influxes, created ideal conditions for thick evaporite deposition.