Cr-Fe metacolloidal nodules from the white carnallite rocks of the Verkhnekamskoe salt deposit

The morphology and composition of the chromium-ferrum metacolloidal nodules from the white carnallite rocks of the Verkhnekamskoe Deposit were investigated. The white carnallite rocks were formed during a tectogenesis by recrystallization of hematite- and goethite-rich carnallite rocks in the presence of acidic hydrogen-containing brines. The brines composition is determined by radiation oxidation of the isomorphic iron (II) and a radiolysis of the crystallization water. It is assumed that the chromium precipitated from sulfate-chloride colloids and later the iron precipitated from chloride brines. Aging of colloidal clots led to the formation of the akaganeite and Cr-akaganeite with a covellite and native phase inclusions.