Skip to the main content

Geologia Croatica, Vol. 77 No. 2, 2024.

Original scientific paper

https://doi.org/10.4154/gc.2024.06

Middle Triassic basaltic pyroclastic rocks from the Mt. Medvednica ophiolitic mélange (NW Croatia): petrology, geochemistry and tectono-magmatic setting

Damir Slovenec orcid id orcid.org/0000-0003-3251-827X ; Croatian Geological Survey, Zagreb, Croatia *
Josip Halamić orcid id orcid.org/0000-0003-3325-5811 ; Croatian Geological Survey, Zagreb, Croatia
Branimir Šegvić orcid id orcid.org/0000-0002-3769-7249 ; Department of Geosciences, Texas Tech University, USA

* Corresponding author.

Full text: english pdf 9.500 Kb

page 57-68

downloads: 20

cite

Abstract

Hectometric blocks of Middle Triassic mafic pyroclastic rocks, represented by volcanic agglomerates/breccias and lapilli tuffs, form part of the ophiolitic mélange of Mt. Medvednica, situated in the southwestern segment of the Zagorje-Mid-Transdanubian Zone. These rocks share petrochemical characteristics with pyroclastic derivatives of alkali, within-plate basaltic lavas of Mts. Medvednica, Samoborska Gora, and Kalnik, indicating the occurrence of explosive events preceding the dominant effusive submarine volcanism during the Middle Triassic (Illyrian-Fassanian?) stages. The formation of these pre-ophiolitic pyroclastics is associated with an intracontinental rift setting and reflects melts derived from an OIB-type enriched mantle plume source. These pyroclastics represent uncontaminated melts that erupted through a highly thinned continental crust. In geodynamic terms, the formation of pyroclastites occurred during the Late Anisian-Early Ladinian along the continental margin of Palaeotethys through the proto back-arc rifting of continental lithosphere (Adria Plate), leading to the formation of the Maliak/Balkan Neotethys Rift, in the emerging northwestern segment of Neotethys. The investigated pyroclastic rocks of Mt. Medvednica document the extension in an evolved intracontinental rift basin, which immediately preceded the generation of the initial Neotethyan oceanic lithosphere during the Upper Triassic.

Keywords

petrology; geochemistry; basaltic pyroclastic rock; , ophiolitic mélange; Middle Triassic; Zagorje-Mid-Transdanubian Zone: Mt. Medvednica; Croatia

Hrčak ID:

318251

URI

https://hrcak.srce.hr/318251

Publication date:

21.6.2024.

Visits: 42 *