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 tectonomagmatic affinity

D. Slovenec, B. Šegvić

Research output: Contribution to journalArticlepeer-review

Abstract

TCLEThis study uses mineralogical, petrological, geochemical, and Sr and Nd isotope data along with K-Ar ages to infer the petrogenesis and geodynamic evolution of Middle Triassic high-K calc-alkaline lavas and their associated pyroclastics of Mt. Kuna Gora in NW Croatia. Their analogue mineralogy and bulk-rock geochemistry testify to the coeval origin of both rock types. Sanidine and plagioclase accompanied by minor augite and Ti-bearing magnetite are the major phases found in a matrix of devitrified volcanic glass and plagioclase microlites. Hydrothermal and diagenetic processes in the pyroclastics originated the formation of chlorite and white mica, and mixed-layer clay minerals, respectively. Petrography reveals the following crystallization order: spinel→clinopyroxene→plagioclase→ alkali-feldspar±Fe-Ti oxides. Geochemical and isotopic data suggests that the studied rocks had a complex origin that included the contamination of subduction-generated magmas by lithospheric mantle melts. This presumes an interplay between fertile arc mantle, subducted continental crust, and depleted or ocean island basalts-like mantle. A low degree of crustal contamination stands as a last step on the formation of such “hybrid” magmas. The subducted Paleotethyan oceanic lithosphere went through processes of partial melting at depths of ~45-49 Km and pressures of ≤1.6GPa and fractionation that produced melts which gave rise to the studied rocks. In the model we are proposing herein such formed partial melts are related to the demise of the northward subduction of the Paleotethys oceanic lithosphere during the Early to Middle Triassic epoch, which is consistent with an active, ensialic mature volcanic arc developing along Laurussian southern active margins.

Original languageEnglish
Article number2
JournalGeologica Acta
Volume19
DOIs
StatePublished - 2021

Keywords

  • Active continental margin
  • Calc-alkaline effusive and pyroclastic rocks
  • Croatia
  • Ensialic volcanic arc
  • Middle Triassic
  • Mt. Kuna Gora

Fingerprint

Dive into the research topics of '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 tectonomagmatic affinity'. Together they form a unique fingerprint.

Cite this