Naslov
Contribution to the knowledge on the low-temperature metamorphism of Mt. Medvednica, Croatia

Autori
Judik, Katalin ; Tibljaš, Darko ; Balen, Dražen ; Tomljenović, Bruno ; Horváth, Péter ; Pamić, Jakob ; Árkai, Péter

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

Izvornik
Euroclay 10th Conference of the European Clay Group Association Abstracts / - Modena, 2003, 144-145

Skup
Euroclay 10th Conference of the European Clay Group Association

Mjesto i datum
Modena, Italija, 22.06.2003. - 26.06.2003

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
low-temperature metamorphism; illite crystallinity; chlorite crystallinity; Medvednica; Croatia

Sažetak
Complex mineral paragenetic, illite and chlorite &#8220 ; crystallinity&#8221 ; , K-white mica geobarometric and microstructural studies were carried out on representative samples from following three pre-Neogene tectono-stratigraphic units of Mt. Medvednica, Croatia: (1) Middle Jurassic&#8211 ; Early Cretaceous ophiolitic mélange ; (2) the Paleo&#8211 ; Mesozoic complex affected by Eoalpine (122-110 Ma) very low- to low-grade regional metamorphism ; and (3) Late Cretaceous&#8211 ; Paleocene overlying flysch sequence. Shales and marls from the matrix of the ophiolitic mélange and from the Cretaceous-Palaeocene sequence are characterized by predominant illite-muscovite, chlorite, quartz, plagioclase and/or calcite, and subordinate dolomite and minor rutile content. The marls and shales are foliated, besides the supposedly bedding parallel foliation a widely spaced, oblique foliation can also be seen. In contrast to the shales and marls, slates from the Paleo&#8211 ; Mesozoic complex contain paragonite moreover the above mentioned phases and show complex microstructural features. Two penetrative foliations can be observed, one is bedding-parallel syn-metamorphic foliation (S1), later crenulated along axial plane cleavage (S2). Similarly to the slates crenulation cleavage (S2) developed in the phyllosilicate-rich intercalations in cipolinos. Illite and chlorite &#8220 ; crystallinity&#8221 ; measurements proved that the pelitic-silty matrix of the Late Jurassic&#8211 ; Early Cretaceous ophiolitic mélange and the Late Cretaceous&#8211 ; Paleocene sequence of Mt. Medvednica are diagenetically altered. Data from the Paleo&#8211 ; Mesozoic complex of Mt. Medvednica indicate that the metamorphism of the unit has reached the high-temperature part of the anchizone (IC = 0.25-0.30 &ordm ; &#916 ; 2&#952 ; ) and, in some cases also the epizone (IC < 0.25 &ordm ; &#916 ; 2&#952 ; ). K-white mica b cell dimension was measured on samples with different lithotypes from the Paleo&#8211 ; Mesozoic complex in order to characterize the pressure conditions of the very low- to low-grade metamorphic rocks. The b values obtained on rock samples with modal compositions adequate for qualitative pressure indications range between 8.986 and 9.040 &Aring ; indicating low to intermediate pressure conditions in the studied area.

Izvorni jezik
Engleski

Znanstvena područja
Geologija, Rudarstvo, nafta i geološko inženjerstvo

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