hrvatski

Naslage s analcimom u Poljanskoj (Slavonija, sjeverna Hrvatska)

Analcime bearing deposits of the Helvetian in Poljanska (southern Papuk, S1avonia) have been investigated. They are developed in two horizons, named »productive horizons« because of their use in cement industry. They have a hybrid composition, owing to the mixture of carbonate sediments (dolomite), pyroclastic and volcanoclastic material of the neighbouring volcanoes and terrigenous detritus derived from older crystalline rocks of the Slavonian mountains. Among different sedimentary members one could determine penecontemporary dolomicrites, miscellaneous pelites (shales, dolomitic marls), tuffs, tuffites and tuffaceous sandstones - all containing analcime crystals as an important component, dispersed or in aggregates. Frequently, monomineral layers or laminae of analcime are formed and interstratified among different sedimentary members. Microscopic, X-ray and chemical investigations suggest that analcime was formed by alteration of volcanic glass, as well as the other silicates, in the shallow water of an unsheltered saline alcaline , lake, under conditions of increased aridity and closure of the lake.

analcim; zeoliti; dolomit; Poljanska; Slavonija

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