engleski

Clay minerals in zeolite deposit of Poljanska, Croatia

Clay minerals in the Lower Miocene zeolite (analcime) deposit of Poljanska (southern slopes of Mt. Papuk, Slavonia, northern Croatia) have been investigated. Complex analyses of lithological members of Poljanska area provide insight into their modal composition and origin (physico-chemical conditions of sedimentation, diagenetic alteration and genesis). Among different sedimentary members contemporary dolomicrites, miscellaneous pelites (shales, dolomitic marls), tuffs, tuffites and tuffaceous sandstones can be distinguished. Variability of mineral composition, texture and structure of sediments belonging to different parts of sedimentary column indicate changes of climate, depth and expansion of the lake, in which sedimentation took place, the kind and amount of detritus. Sediments deposited in fresh- to brackish-water lake, represented by calcareous-marly rocks, in which clay minerals are represented by montmorillonite as a product of a volcanic glass alteration can be found in the bottom and in the middle of the sedimentary column. With increasing salinity and alkalinity of lake water, quantity of montmorillonite diminishes. Illite is the dominant clay mineral in the layers of authigenic analcime bearing dolomicrites, pelites and tuffites deposited in the saline-alkaline lake.

climate; sedimentation; alteration; clay minerals; Poljanska

nije evidentirano