Abstract
Minerals are deposited when evaporation is greater than atmospheric precipitation. Calcium sulfates are one of the most important evaporative minerals which have been expanding over the past few years. In the formation of these minerals, various sedimentary and diagenetic processes play a role from shallow ridges to deep water. The research investigated the types of evaporative minerals (with an emphasis on anhydrite) in Gachsaran Formation in Gotvand dam range (25 km north of Shoushtar city). Investigating the thin sections of evaporative samples of this formation led to the identification of various anhydrite textures. Also, the existence of the main phases of calcium sulfate and NaCl by XRD analyses on a number of samples. The formation of anhydrite, gypsum and halite minerals in Gachsaran Formation in Lagoon and Sabkha environments was identified texture. The most important textures were laths anhydrite, nodule, isolated, radial anhydrite crystals, and porphyroblastic gypsum crystals, most of which are formed at the same stage of precipitation or in the early stages of diagenesis.
Highlights
Evaporatives include a wide range of chemical deposits which are resulted through evaporation of inspissated brines from or near the surface of the earth [1] [2]
The research investigated the types of evaporative minerals in Gachsaran Formation in Gotvand dam range (25 km north of Shoushtar city)
In the following before examining the types of anhydrite crystalline materials, first we briefly describe the types of facies of Gachsaran Formation
Summary
Evaporatives include a wide range of chemical deposits which are resulted through evaporation of inspissated brines from or near the surface of the earth [1] [2]. The main evaporative minerals include gypsum, anhydrite and halite. Most of the old evaporatives are mostly due to the increase in concentrations of saline waters with a source of seawater [5]. Geological evidence and present-day events show that two minerals of gypsum and anhydrite are deposited on the surface of the earth underwater (in shallow and deep water) and inland (in coastal and subaerial sabkhas) [6]. Gypsum formation occurs under low temperature-pressure conditions and low salinity levels. Anhydrite is formed at higher temperature-pressure and higher salinity levels
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