Anhydrite and gypsum in the Devonian and Permian evaporite lithofacies of Belarus: a review

摘要

Anhydrite is widespread in the Prypiac Trough in the form of beds and nodules in the Subsaliferous Terrigenous and Carbonate formations (Eifelian and Frasnian), the Lower Saliferous Formation (Frasnian), the Intersaliferous and Upper Saliferous formations (Famennian). It is also present in the Asselian and Sakmarian (Lower Permian) deposits of the trough. The anhydrite is grey, blue, pink and orange. It has massive and, more rarely, horizontal bedding, and a fine- and micro-crystalline structure. Gypsum extends widely across the Ora Depression, Zlobin and Latvijas Saddles and partly in the Belarusian Anteclise, where it lies within the Eifelian deposits. It is also found in the Frasnian strata of the North-Prypiac Shoulder. As a component of facial analogue of the Upper Saliferous Formation gypsum forms the Bryniou deposit in the west of the Prypiac Trough. This mineral is also observed in the Oversaliferous Formation (Famennian) and in the Asselian and Sakmarian strata of the trough. There are spar, saccharoidal, alabastrine and selenitic varieties of gypsum. A medium to coarse crystalline structure is typical. The gypsum is grey, pink, yellow or orange.