Middle Triassic high-K calc-alkaline effusive and pyroclastic rocks from the Zagorje-Mid-Transdanubian Zone (Mt. Kuna Gora; NW Croatia) : mineralogy, petrology, geochemistry and tectono-magmatic affinity
Slovenec, Damir (Croatian Geological Survey)
Šegvić, Branimir (Department of Geosciences. Texas Tech University)

Date:	2021
Abstract:	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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Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Middle Triassic ; Calc-alkaline effusive and pyroclastic rocks ; Ensialic volcanic arc ; Active continental margin ; Mt. Kuna Gora ; Croatia
Published in:	Geologica acta, Vol. 19 (2021) , p. 1-23 (Articles) , ISSN 1696-5728

Adreça original: https://raco.cat/index.php/GeologicaActa/article/view/384251
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2021.19.2
DOI: 10.1344/GeologicaActa2021.19.2

23 p, 13.1 MB

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