Morphological features of gypsum particles depending on the hydrodynamic conditions of their formation (at the Novomoskovsk evaporite basin)

Abstract

Introduction: The Novomoskovskoe gypsum deposit, part of the evaporite basin of the same name, is the largest in the world. Gypsum-bearing strata are confined to the Kudeyarovsky layers of the Upper Famennian substage of the Devonian system and are represented by interlayering of dolomites, clays, and several modifications of gypsum. Analytical studies were carried out using a Jeol 6380-LV scanning electron microscope. The samples for analysis were fresh chips of minerals. Results and discussion: When examining gypsum particles under an electron microscope, different arrangements of its needle-shaped and columnar particles and their internal structure were revealed. It has been established that such a variety of gypsum as selenite is formed in the calm hydrodynamic environment of deep-sea lagoons, where the fallen sediment is not affected by wave influences and underwater currents. When sediment is agitated, the growth of crystals in one direction is disrupted, and the gypsum layers acquire a tangled fibrous texture. Conclusions: Regardless of the lithological features of gypsum, its crystals have a needle-columnar shape. Complexly arranged acicular-columnar gypsum crystals, composed of plates located perpendicular to their long axis, indicate the formation of gypsum in saline lagoons, directly from supersaturated solutions, and not through the transformation of anhydrite.