Naslov
Mineralogy and geochemistry of Upper Miocene pelitic sediments of Zagorje Basin (Croatia): Implication for evolution of Pannonian Basin

Autori
Grizelj, Anita ; Tibljaš, Darko ; Kovačić, Marijan

Izvornik
Geologica Carpathica (1335-0552) 58 (2007), 3; 263-276

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

Ključne riječi
clay minerals; chemical composition; Upper Miocene; Zagorje Basin; marl; X-ray diffraction

Sažetak
Abstract: According to X-ray powder diffraction analyses of Upper Miocene pelitic sediments from Zagorje Basin all of the samples contain same mineral species, but in significantly different quantities. Calcite is a dominant component in most of the samples (31-74 wt. %), clay minerals (18-50 wt. %), quartz (5-21 wt. %) and feldspars (1-5 wt. %) are less abundant, while dolomite and pyrite are present only in few samples. Among clay minerals, in < 2 &#956; m insoluble residue fraction, smectite, illite, chlorite and kaolinite were determined. Dominant constituents in 0.09-0.16 mm fraction, as determined by optical microscopy, are quartz, feldspars, rock fragments (chert, quartzite and schists) and micas. Chlorite, limonite, pyrite, garnet, tourmaline, zircon, epidote and staurolite are present in small amounts. Pelitic sediments within older (Upper Pannonian) investigated sediments are, in accordance with mineral composition of insoluble residue and CaCO3 content, classified as marls, while those in the younger (Lower Pontian) sediments are silty marls. Observed gradual decrease in carbonate content, and simultaneous increase of clayey-silty component, going from older to younger deposits, is the result of the gradual increase of teriggenous influence. Mineral composition of marls together with elemental ratios critical of provenance (SiO2/Al2O3, K2O/Na2O, Eu/Eu*, La/Sc, Th/Sc, Th/Co, Th/Cr and La/Co) and source rock discrimination diagrams (Fe2O3-K2O-Al2O3 and La-Th-Sc), point out that source rocks were from the Upper Crust and remarkably felsic in nature. Chemical composition of the sediments and modal composition of silt-size fraction indicate Alpine provenance of clastic material.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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