Naslov
Evidence from chloritoid schists for muli-stage metamorphism in the Mt. Medvednica area (Zagorje Mid Transdanubian zone, N Croatia)

Autori
Mišur, Ivan ; Belak, Mirko ; Klötzli, Urs ; Balen, Dražen

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

Izvornik
Mitteillungen Österreichischen Mineralogischen Gesellschaft / Koller, F. ; Kolitsch, U. ; Tessadri, R. - Beč, 2015, 89-89

Skup
MinPet2015

Mjesto i datum
Leoben, Austrija, 10.09.2015. - 13.09.2015

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Chloritoid; schist; Medvednica

Sažetak
Chloritoid schists form a part of the Palaeozoic - Mesozoic succession and represent one of the oldest lithology in the Mt. Medvednica area in N Croatia. Regionally Mt. Medvednica belongs to the Zagorje Mid Transdanubian zone, a transition area between the Alps and the Dinarides. The presented results are a part of an ongoing study of metasedimentary rocks of Mt. Medvednica. Samples were collected from the SE slopes of Mt. Medvednica. Accessory minerals in the chloritoid-bearing schists are tourmaline, zircon, apatite, monazite, xenotime and rutile. XRD, XRF, LA-MC-ICP-MS, SEM, electron microprobe and microstructural investigations were used to determine the chemical composition, microstructural features, thermo-barometric conditions and the morphology of zircons of the chloritoid schists. Chlorite-chloritoid thermometry and intersection of phengite, chlorite and chloritoid isopleths in the MnNCKFMASHTO pseudosection suggests the presence of a relict high-pressure metamorphic event at approximately 13-14 kbar and 410-440°C and equilibration of chlorite and white mica within subsequent greenschist-facies P-T conditions at approximately 8 kbar and 350-400°C. Thermometry of chlorite and chloritoid give unexpectedly high temperatures over 500°C. Zircon typology suggests that there could be at least two sources of zircon grains based on the Pupin classification. One source is possibly detrital made up by plutonic, stubby zircons. The other source of zircon grains could be of volcanic, with typically elongated crystals showing growth spindle inclusions. Based on the results of microstructural analysis the possible protolite of the chloritoid-bearing schists could be argillaceous sandstones. Geochemical data suggest that these could be derived from acid magmatic rocks. The whole rock composition of La–Th–Sc and Th–Sc–Zr/10 suggests that possible depositional environment very likely represents a continental arc environment. Carbonate intercalations within the argillaceous sandstones could indicate deposition in a marine environment. Zircon typology indicates the input of volcanic material during deposition. Pseudosection modeling indicate that the P-T path probably is a result of multi-stage metamorphism.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA