Naslov
Correlation of illite Kübler indices and results of Raman spectroscopy of carbonaceous material from metasedimentary rocks from NW Croatia

Autori
Topalović, Ena ; Rantitsch, Gerd ; Balen, Dražen ; Tibljaš, Darko

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

Izvornik
10th Jubilee Mid-European Clay Conference Book of Abstracts / Gorniak, Katarzyna ; Szydlak, Tadeusz ; Sek, Mateusz - Krakov : Wydawnictwo Naukowe Akapit, 2022, 91-91

ISBN
978-83-65955-60-9

Skup
10th Mid-European Clay Conference

Mjesto i datum
Kliczków, Poljska, 11.09.2022. - 15.09.2022

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
clay minerals, Kübler index, Raman spectroscopy, diagenesis, very-low grade metamorphism

Sažetak
The Kübler index (KI), i.e. the width (in Δ°2θ) of the illite 001 diffraction peak, as determined by X-ray diffraction on the <2 µm clay fraction, and Raman spectroscopy of carbonaceous material (RSCM) were used to distinguish the peak metamorphic temperatures of rocks from NW Croatia, previously considered to be non-metamorphosed. The analyses were performed on the Late Paleozoic black shales belonging to the northwesternmost part of the Internal Dinarides sampled in the Samobor-Žumberak Mountains and the Marija Gorica Hills, and on the Triassic (Upper Ladinian) carbonaceous dolomites belonging to the post-Variscan Alpine overstep sequences of the Tisia Mega-Unit found in the western part of the Papuk Mountain. The study was carried out within the frame of a wider investigation of low-grade metamorphic rocks in northern Croatia to explain some inconsistencies in the KI values obtained so far. A total of 12 rock samples, including 3 dolomite samples rich in organic carbon, were used to correlate the measured KI values with RSCM temperatures. XRD analysis of the Late Paleozoic black shales shows a dominance of illite, accompanied by chlorite. The KI values obtained range from 0.29 to 0.35 Δ°2θ, indicating that the black shales underwent anchizonal thermal alteration. The clay minerals in carbonaceous dolomites are illite and kaolinite. The KI value of 0.62 Δ°2θ indicates a diagenetic alteration. Raman spectra of organic material extracted from black shales show an estimated peak temperature in the range 275-285 °C, consistent with the KI values. In contrast, the Raman data from dolomite samples (285°C) contradict the diagenetic KI value, implying that the organic material in carbonaceous dolomites could be detrital. However, the KI of the surrounding rocks in the western part of Papuk are in agreement with the anchizonal metamorphism. Further analyses are required for a better understanding of the thermal history of the studied area.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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