Analysis of Structure and Textures of Anhydrite Mineral in Gachsaran Formation in Gotvand Area, Iran

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.

Petrographic Record and Conditions of Expansive Hydration of Anhydrite in the Recent Weathering Zone at the Abandoned Dingwall Gypsum Quarry, Nova Scotia, Canada

“…Such relations indicate that the gypsum crystallized forming the epitaxial intergrowth with anhydrite [31,91]. Locally, the anhydrite is replaced by gypsum in a pseudomorphic manner (Figure 6h,j) without changing the original crystal shape outline [106]. The course of pseudomorphic replacement of anhydrite by gypsum is well visible when a grain of anhydrite is replaced only partly by gypsum (Figure 6h,j).…”

Investigative study of the potentialities of noble applications for the Brazilian calcium sulfate α-hemihydrate

“…Another plausible hypothesis to justify the discrete events observed in the graph shown in Figure 3 may be related to the evaporation of the remaining water in the crystalline structure of the α plaster sample, object of study of this work, with the probable formation of anhydrite. It is not uncommon to find references in the literature that point to the formation of anhydrous calcium sulphate related to the complete dehydration of calcium sulphate hemihydrate (Canut 2003 apud Canut 2006;Costa 2013;Marandi et al 2017).…”

Variations in carbonate-evaporite shoreline and ramp facies trends: Middle Miocene Fatha Formation, Kurdistan Region, NE Iraq

“…A further study argued that the formation accumulated in a stormaffected evaporitic basin subjected to freshwater influxes (Ameen and Karim, 2007). Moreover, other studies have documented a stratigraphic equivalent to the Fatha Formation, the Gachsaran Formation in Iran, which is also characterized by shallowing-upward cycles capped by evaporites that are interpreted to have accumulated in supratidal and sabkha environments (James and Wynd, 1965;Gill and Ala, 1972;Pirouz et al, 2011;Soleimani, 2015;Marandi, 2019;Mahmoodabadi, 2020). Thus, the origin and environmental significance of the preserved cycles of the Fatha Formation remain contentious.…”