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Conditions of dolomitization at selected localities of the Barrandian
Novotný, Petr ; Zachariáš, Jiří (advisor) ; Suchý, Václav (referee)
Research on dolomitic limestones and dolomites from selected localities of the Barrandian, stratigraphically related to the Scyphocrinites Horizon near the Silurian-Devonian boundary, showed the occurrence of two distinct types of dolomite - diagenetic and epigenetic - differing in petrography and genesis. The diagenetic dolomite is quantitatively predominant. It is finely to moderately coarsely grained with crystal size from 20 μm to 450 μm. Crystals of this dolomite form mostly xenotopic and hypidiotopic textures (occasionally even idiotopic). This type of dolomite formed at low temperature and depth by recrystallization of a carbonate mud during early diagenesis, or during subsequent deeper burial. It is also possible that it originated from recrystallization of previously formed syngenetic dolomite. Fine texture of the diagenetic dolomite is a proof of fast dolomitization and of formation of numerous crystallization centers. Very fine-grained variant of dolomite was also detected (forming aphanotopic texture, size of crystals below 0,002 mm). The epigenetic dolomite, also known as baroque or saddle dolomite, is less common than the former one. It forms white, milky-turbid or clear crystals of large dimensions (0.8 - 3.1 mm). The shapes of these crystals are conspicuous, variously twisted,...
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