Naslov
Mineral and chemical composition of rudist valves from Upper Cretaceous limestones of southern Istria, Croatia

Autori
Tibljaš, Darko ; Moro, Alan ; Ostrež, Željka

Izvornik
Geologia Croatica : journal of the Croatian Geological Survey and the Croatian Geological Society (1330-030X) 57 (2004), 1; 73-79

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
rudist valves; mineral composition; trace element content; Turonian to Upper Santonian; Istria; Croatia

Sažetak
Turonian to late Santonian limestones of southern Istria are rich in rudist remains. The main aim of this study was to determine the mineral and chemical composition of 22 samples of rudist valves belonging to the genera Durania, Praeradiolites, Radiolites, Gorjanovicia and Vaccinites, and to explain any observed differences. X-ray diffraction and chemical analyses showed that in all the analysed samples, the primary constituents of rudist shells, aragonite and low-Mg calcite, were transformed into diagenetic low-Mg calcite. The strontium concentrations of all the analysed shells correspond to pelagic bulk rock samples altered by diagenesis and are significantly lower than those for biological calcite. Observed differences in the chemical composition of diagenetically altered rudist shells belonging to different rudist genera, namely a slightly higher content of Sr in specimens of Gorjanovicia and Durania and lower concentrations of Mg in shells of Vaccinites are most probably the result of different shell structures and original mineral constituents.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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