منشاء نهشته هاي تبخيري پتاس دار ميوسن در شمال حوضه كوير بزرگ ، جنوب سمنان

Origin of Potash-bearing Evaporites in the North of the Great Kavir Basin, South of Semnan

Studied potash-bearing evaporates are situated in the northern parts of the Great Kavir desert, south of Semnan city. These deposits, which could be classified as Mg-SO4 poor salts, belong to the lower parts of the Miocene Upper Red Formation. As well as halite, which is the main mineral, they contain primary sylvite and camallite, and some secondary K-Mg bittern salts such as polyhalite, dʹansite and langbeinite. Surface and bottom nucleated chevron, cornet and cumulative textures in halite and sylvite indicates their early crystallization from parent brines in the shallow evaporitic ponds. Secondary K-bearing salts, which have been formed during shallow burial diagenesis, are polyhalite, dʹansite and langbeinite. High bromine contents, simple mineralogical paragenesis of these salts and their association with marine carbonates indicate their marine origin. Accordingly, a subsidizing relatively shallow marginal marine basin, under domination of arid climate, could be suggested for sedimentary environment of these evaporites.