Naslov
Occurrence of bentonite in Sarmatian deposits of the Zagorje Basin (Croatia)

Autori
Grizelj, Anita ; Čaić Janković, Ana ; Kovačić, Marijan

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Special Issue, Journal of Faculty of mining, geology and civil engineering / Dervišević, Rejhana ; Vrabac, Sejfudin ; Babajić, Elvir ; Đulović, Izudin - Tuzla : University of Tuzla, Faculty of mining, geology and civil engineering, 2022, 31-32

Skup
9th International Workshop Neogene of Central and South-Eastern Europe

Mjesto i datum
Tuzla, Bosna i Hercegovina, 06.06.2022. - 09.06.2022

Vrsta sudjelovanja
Poster

Vrsta recenzije
Podatak o recenziji nije dostupan

Ključne riječi
Zagorje Basin, Bentonite, Sarmatian, XRD, DSC

Sažetak
The investigated outcrop Sutla -II is located in the northwestern part of Croatia, near the river Sutla and the state border with Slovenia. It belongs to the Zagorje Basin, which is part of the Pannonian Basin System. The section consists of about 45 m thick deposits of Lower Sarmatian age (GRIZELJ et al., 2015). Sediments were deposited in two different depositional environments of reduced salinity: near shore and offshore. Near shore deposits composed of conglomerates, sandstones, biocalcirudites, biocalcarenites, marls and 10 cm thick layer of bentonite, while offshore deposits contain marls and silts with sand intercalations. The bentonite from Sutla-II section is light gray color, homogeneous, structurless layer. Although the occurrence of pyroclastic rocks and bentonites is common in the Middle Miocene, their occurrence is more common in Badenian than in Sarmatian (PÜSPOÜKI et al., 2005 ; PAVELIĆ & KOVAČIĆ, 2018). The aim of this study was to investigate bentonite layer from Sutla-II section by mineralogical methods such as X-ray diffraction (XRPD) and thermal analyses. XRPD patterns were recorded on random mounts of bulk samples and oriented mounts of the <2 µm fraction using the Philips vertical goniometer (type X`Pert). Experimental conditions was 45 kV, 40 mA, PW 3018/00 PIXcel detector, primary beam divergence 1/4° and continuous scan (step 0.02 °2θ/s). Oriented mounts of the <2 µm fraction were recorded after the following treatments: a) air drying, b) ethylene-glycol solvation, c) saturation with K+ d) saturation with Mg2+ e) K+ saturation and ethylene-glycol solvation, f) Mg2+ saturation and ethylene-glycol solvation, g) heating to 400°C and 550°C. Determination type of smectite were obtained procedure described by GREEN-KEELY (1953 ; 1955) which included Li+ saturation, heating to 200°C and then treated with glycerol. Thermal analysis was perform using a Mettler Toledo TGA/DSC2 instrument. Sample (about 40 mg) was placed in aluminium oxide crucibles and an empty crucible was used as a reference material. Experimental conditions were: the heating rate 10 °C /min in the 25 – 1100 °C range in N2 atmosphere (flow rate: 50 ml/min). Analysed bulk samples of bentonite predominantly contains low charge, dioctahedral smectite and minor amount of cristobalite and amorphous substance (presumed to be volcanic glass). According to Green-Keely test, analysed smectite was classified as montmorillonite. DSC curve of sample show a double endothermic peak at 100 and 160 °C assigned to the dehydration process, another endothermic peak at 680 - 740 °C assigned to dehydroxylation and one exothermic peak around 1000 °C due to recrystallization. A standard sample of Ca-montmorillonite (STX-1b - Clay Minerals Society) which was recorded under the same experimental conditions as our sample showed a very similar DSC curve. This could mean that the smectite from the bentonite from section Sutla-II is also Ca-montmorillonite. However, for determination that is more accurate it is necessary to do a chemical analysis of the sample. In addition, future research should include radiometric methods to confirm the age of bentonite obtained by paleontological analysis. This study was partly supported by Croatian Science Foundation Project – SEDBAS, IP-2019-04- 7042. REFERENCES: GREENE-KELLY, R. (1953): Irreversible dehydration in montrnorillonite. Part II: Clay Mineral Bull. 1, 52-56. GREENE-KELLY, R. (1955): Dehydration of montmorillonite minerals: Mineral. Mag. 30, 604- 615. GRIZELJ, A., MIKNIĆ, M., AVANIĆ, R., BANAK, A., WACHA, L., KUREČIĆ, T. & BAKRAČ, K. (2015): Peleoecological and sedimentological sharacteristics of Sarmatian sediments from the Hrvatsko Zagorje Basin (Croatia), In: BLUM, M. (Ed.): Abstracts of 31st IAS Meeting of Sedimentology (). Krakow: Polish Geological Society, 217-217. PAVELIĆ, D. & KOVAČIĆ, M. (1999): Lower Miocene alluvial deposits of the Požeška Mt. (Pannonian Basin, northern Croatia): cycles, megacycles and tectonic implications. Geol. Croat., 52, 67–76. PÜSPOÜKI, Z., KOZÁK, M., KOVÁCS-PÁLFFY, P., FÖLDVÁRI, M., McINTOSH, L. W. & VINCZE, L. (2005): Eustatic and tectonic/volcanic control in sedimentary bentonite formation - a case study of Miocene bentonite deposits from the Pannonian Basin, Clays and Clay Minerals, 53/1, 71-91.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA