Middle Triassic high-K calc-alkaline effusive and pyroclastic rocks from the Zagorje-Mid-Transdanubian Zone (Mt. Kuna Gora
This study brings the mineralogical, petrological, geochemical, Sr and Nd isotope data as well as K-Ar ages used to infer on petrogenesis and geodynamic evolution of Middle Triassic high-K calc-alkaline effusives and their associated pyroclastites of Mt. Kuna Gora in NW Croatia. Their matching miner...
| Autores: | , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | Universitat Autònoma de Barcelona |
| Repositorio: | Dipòsit Digital de Documents de la UAB |
| Idioma: | inglés |
| OAI Identifier: | oai:ddd.uab.cat:250174 |
| Acceso en línea: | https://ddd.uab.cat/record/250174 https://dx.doi.org/urn:doi:10.1344/GeologicaActa2021.19.2 |
| Access Level: | acceso abierto |
| Palabra clave: | Middle Triassic Calc-alkaline effusive and pyroclastic rocks Ensialic volcanic arc Active continental margin Mt. Kuna Gora Croatia |
| Sumario: | This study brings the mineralogical, petrological, geochemical, Sr and Nd isotope data as well as K-Ar ages used to infer on petrogenesis and geodynamic evolution of Middle Triassic high-K calc-alkaline effusives and their associated pyroclastites of Mt. Kuna Gora in NW Croatia. Their matching mineralogy and bulk-rock geochemistry testify on coeval origin of both rock types. Sanidine and plagioclase accompanied by minor augite and Ti-bearing magnetite are major phases merged in a matrix made of devitrified volcanic glass and plagioclase microlites. Hydrothermal and eogenetic alterations documented in pyroclastites gave rise to the formation of chlorite/white mica and mixed-layer clays, respectively. Rocks' petrography unveiled the following crystallization order: spinel → clinopyroxene → plagioclase → alkali-feldspar ± Fe-Ti oxides. Geochemical and isotopic evidences point to a complex origin of studied rocks which included the contamination of subduction-generated magmas by melts derived from lithospheric mantle. This presumes an interplay of the fertile arc mantle, old(?) continental crust, and depleted or OIB-like mantle. A low degree of crustal contamination stands as a last phase of the formation of such "hybrid" magmas. The subducted Paleotethyan oceanic lithosphere went through the processes of partial melting of mantle source placed at depths of ~45-49 km and pressures ≤ 1.6 GPa and subsequent fractionation which produced melts parental to studied rocks. Suggested model is linked to the demise of northward subduction of Paleotethys during the Early Mid-Triassic, which is in favor of an active, ensialic mature volcanic arc developed along the southern active continental margins of Laurussia. |
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