Application of X-Ray diffraction analysis for sedimentological investigation of Middle Devonian dolomites from Northeastern Bulgaria

Pages: 
pp. 31-38
Geological Institute, Bulgarian Academy of Sciences, Sofia 1113, Acad. G. Bonchev St., Block 24, Sofia 1113, Bulgaria
Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Block 107, Sofia 1113, Bulgaria
Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Block 107, Sofia 1113, Bulgaria
Abstract: 

The studied Middle Devonian (Givetian) dolomites occur in three well sections: OP-2 Mihalich, R-119 Kardam and R-1 Vaklino (Northeastern Bulgaria). Two general genetic dolomite groups are distinguished and interpreted on the basis of performed XRD analyses and petrographic observations. The first one is represented by early diagenetic crypto- to microcrystalline dolostones that are characterized by nearly stoichiometric composition (from 51.0 to 51.7 mole % CaCO3) and degree of order ranging from 0.50 to 0.91. They are interpreted as products of rapid precipitation in an arid peritidal (sabkha) environment with hypersalinity of the water milieu and elevated Mg/Ca ratio of the dolomitizing solutions. The second group includes late diagenetic medium crystalline dolostones that have almost stoichiometric composition (from 50.0 to 51.3 mole % CaCO3) and higher degree of order (from 0.77 to 1.18) indicating a possible slow crystallization process and precipitation from dilute solutions at elevated temperatures in an open diagenetic system. A part of them might have also resulted from neomorphic alteration of precursor metastable dolomite phases.

Keywords: 

dolomite, X-ray diffraction, Middle Devonian, Northeastern Bulgaria

VOLUME 40 (1-3)/December 2011

Sofia University “St Kliment Ohridski”, Faculty of Geology and Geography, 15 Tzar Osvoboditel, 1504 Sofia, Bulgaria

National Museum of Natural History, Bulgarian Academy of Sciences, 1, Tsar Osvoboditel Blv., 1000 Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, Sofia 1113, Acad. G. Bonchev St., Block 24, Sofia 1113, Bulgaria
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Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Block 107, Sofia 1113, Bulgaria
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Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Block 107, Sofia 1113, Bulgaria

Czech Geological Survey, Klarov 3/131, 118 21 Praha 1, Czech Republic
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Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev St. Bl. 24, 1113 Sofia, Bulgaria

Faculty of Geology and Geoenvironment, University of Athens, Platanon 16b, 14578, Athens, Greece
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Odyssea Elyti 15, 13341, Athens, Greece

Geological Institute, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 24, 1113 Sofia