Glaukonite from Deposits of Different Age in Mountain Crimea

Abstract

The article describes glauconites, which in stratigraphic section of the Crimean Mountains, are mainly localized among Alb-Cenomanian, Maastricht-Danian and Eocene deposits. The study of isolated mono fractions made possible to identify the characteristics of glauconites of different ages and different generations. Three generations are distinguished, reflecting a sequential series of glauconite transformation at different stages of sedimentary rock formation. Generations differ in density, electromagnetic, structural, and chemical properties. Together, they allow to consider glauconites as heterogeneous illite formations with a variable content of swelling smectite layers, replaced by “hard” illite packets. This led to stabilization of the glauconites structure and their self-purification from Mn, Ti, V, Cr, Ni, Co, Cu, Zn. At different stratigraphic levels glauconites also differ in trace contaminants. In Alb-Cenomanian glauconites V, Cu, Zn accumulate above Clark. Danian varieties are enriched in Cr and a little in V, and Eocene glauconites - Mn, Ni, Co, and B. The glauconites formation was an intermittent, multi-stage, recycling process. Their main mass was formed during diagenetic crystallization of Al-Fe-Si gel. The process was repeatedly interrupted by sediments’ rewashing and roiling by waves and currents. Then the glauconites formation renewed again in the form of microconcretions or of outgrowths, coatings, and shells over rewashed glauconite grains. The maximum concentration of glauconite occurred at elevated offshore areas during erosion and rewashing of glauconite-containing sediments, as well as in depressions below the wave erosion base. Diagenetic glauconite formation was optimally combined with the accumulation of glauconite grains, transported by sea heaving and currents.