2015 Volume 25 Issue 3 Pages 249-251
In this paper, we consider the results of special investigation into the composition and properties of different types of salt accumulations sampled from the surface salt crust of Solonchak in Uzbekistan. The soil profiles were dug in the dry delta of the Zeravshan River in Uzbekistan. The surface salt crust of the crusty Solonchak can be differentiated into three major morphological types. The particular minerals were diagnosed with a help of X-ray diffraction and thermogravimetric (TG), microscopes Olympus BX 51 and SEM. Chemical analyses of water extracts from these types of the crust suggest that all of them consist of a mixture of sodium and magnesium sulfates and chlorides with somewhat different Cl/SO4 ratios. The appearance of high alkalinity in the first type of the crust might be related to the activity of microbiota concentrated in certain microzones. Micromorphological and mineralogical investigations showed that each morphological type of the salt crust is characterized by its own paragenetic association of mineral salts with a predominance of sodium and magnesium sulfates: thenardite, mirabilite, and bloedite (astrakhanite); more careful examinations with the use of TG and SEM techniques have shown the presence of glauberite, polyhalite, and gypsum. It is important that only a combination of different investigation techniques makes it possible to identify different minerals of salts in their mixture and suggest a reliable interpretation of the obtained data.
