Naslov
The Protholite Age of Greenschists of Medvednica Mt. (NW Croatia)

Autori
Belak, Mirko

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

Izvornik
6. hrvatski geološki kongres s međunarodnim sudjelovanjem. Knjiga sažetaka. 6th Croatian Geological Congress with international participation. Abstract Book / Horvat, Marija ; Matoš, Bojan ; Wacha, Lara - Zagreb : Hrvatski geološki institut, 2019, 23-23

Skup
6. hrvatski geološki kongres s međunarodnim sudjelovanjem

Mjesto i datum
Zagreb, Hrvatska, 09.10.2019. - 12.10.2019

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Domaća recenzija

Ključne riječi
Medvednica Mt., greenschists, protholite age, Conodonts, Radiolarian

Sažetak
The Medvednica Mt. is located in the north-western Croatia, in the Zagorje-Mid-Transdanubian Shear Zone, in the junction area of geotectonic units Alps, Tisza and Dinarides. The main greenschist mass is found in the central part of Medvednica Mt. (Malo and Veliko Sljeme – Puntijarka), while small occurrences, in the form of tectonic zones and in the sinsedimentation position with metasediments could be found in the north-eastern part of Medvednica Mt., stretched from the village Mikulić in the southwest to the Blaguša stream north of Kobiljak locality. According to the preserved relicts of the ophitic structure and greenschist geochemical analysis, basalt and diabase with characteristics of enriched N-MORB, have been confirmed to be the protholite rocks. Metamorphic changes were crea- ted by subduction-collision processes from middle Jurassic to Lower Cretaceous in the greenschists facies, at tempera- tures from 350 °C to 450 °C and pressure of 3 to 4 kbar. The greenschist of Medvednica Mt. is closely associated with different lithostratigraphical units of metasediments: 1) The main greenschist mass is associated with metaradi- olarite, quartz-chlorite schist, and thinner interlayers of ankeritized metacarbonate. Fossiliferous content in rocks (radiolaria and filaments) didn’t allow the protholite age stratigraphic determination of parametamorphites. In the Alps-Dinaric region, from the lithofacies point, the protholite rocks could be positively correlated with the Middle-Upper Triassic and Jurassic lithofacies. 2) The greenschist interlayered with recrystallized lime- stone. The recrystallized limestone is determined as mid-dle Triassic, Anisian (Bithynian-Illyrian) on the basis of the conodonts. 3) Small greenschist bodies associated with the dark meta- psamites, black calcitic metapelites and black silty recrys- tallized limestones. In the recrystallized black limestones, conodonts are typical for the Upper Ladinian (Upper Longobardian ) - Lower Carnian (Cordevolian). 4) The greenschist (metadiabase) associated with the meta- morphosed limestone and the dark metapelite. Based on conodonts and graptolite metasedimentes, Paleozoic age was determined. Greenschist protholite is diabase, assumed to have been created in Permian-Triassic syn-rift phase.The protholite rocks (basalt and diabase) age for cer-tain greenschists were determined to be Middle Triassic, Anisian (Bithynian-Illyrian) and Upper Ladinian (Upper Longobardian) – Lower Carnian (Cordevolian). Basalt, the protholite rocks of the main greenschist mass of Medved-nica Mt. is assumed to be Middle-Upper Triassic or Jurassic age. The geotectonic position of greenshist protolite rock could be connected to the magmatic activity during the syn-rift Triassic phase and to the formation of western Tethy- an oceanic realm.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA