Environment of potassium-magnesium salt formation in the Upper Permian Kaliningrad-Gdansk block of the Central European halogenbasin (from examination of inclusions in minerals)

Abstract

Examination of inclusions in minerals makes the basis for analyzing the peculiarities of salt crystallization in the Kaliningrad-Gdansk halogen block of the Central- European evaporite basin. Most of the studied sections are composed of fine – medium- grained rock made of halite impregnated with polyhalite, kieserite, carnallite and kainite. Three systems of micronclusions maybe distinguished among the wide diversity of inclusions: 1) inclusions of mineral-forming mediums; 2) inclusions of surrounding mediums; 3) solid inclusions captured by minerals during their growth from marine solutions. Thedead-endposition of the study basin accounts for the solutions enrichment in potassium and magnesium arriving from the neighboring German-Polish halogen-bearing areas. The in flowing brine was desalinated by continental waters enriched in calcium and sulfate ions. This used to result increating conditions for polyhalite precipitation. The presence off latboat-shaped structures in halite and in kainite grains is most probably indicative of surficial crystallization of potassium and potassium-magnesium minerals. Carnalliteandbischofiteimpregnationsarerecordedinhalite, whichis indicative of theeutonicstagein the basin development and of manifestations of bottom crystallization of minerals and, accordingly, of the brine probable stratification. Therefore, at the moment of crystallization of potassium and potassium-magnesium minerals, the basin was peculiar for availability of two-layered brine.