Mesozoic Igneous Suites in Hungary: Implications for Genesis and Tectonic Setting in the Northwestern Part of Tethys

Mesozoic igneous rocks occur in various tectonic units of the Intra-Carpathian Area of Eastern Europe. These rocks were situated several hundred km apart from one another during their formation, and subsequent large lateral displacements resulted in their present positions. They formed during a relatively wide temporal range (Middle Triassic to Late Cretaceous) through different petrogenetic processes associated with the Mesozoic evolution of the northwestern part of Tethys.

In the Transdanubian subunit of the Alcapa block, Middle Triassic calc-alkaline, intermediate-to-acidic, and potassic rocks occur as pyroclastics, lava flows, and dikes in the Bakony and Buda mountains. The Gemer-Bükk subunit of the Alcapa block comprises two different igneous series: (1) slightly metamorphosed Middle Triassic volcanic rocks of the Eastern Bukk Mountains, which can be divided into an older (Anisian-Early Ladinian) calc-alkaline, intermediate-to-acidic volcanic series and a younger (Late Ladinian) alkaline basaltic series; and (2) two series of the Middle Triassic to Middle Jurassic ophiolite complex (Bódva Magmatic Series and Darnó-Szarvaskö Magmatic Series), embedded in a tectonic melange and in an olistostrome suite along a SW-NE-oriented zone. The Tisza block contains Early Cretaceous alkaline volcanic rocks in the Mecsek-Alföld subunit.

Strong temporal and geochemical correlations have been observed between the Middle Triassic volcanic rocks of the Bakony and Buda mountains and the Southern Alps, and those of the Eastern Bükk Mountains and the Outer Dinarides. We propose that all these rocks were formed during the same extension-related volcanic activity along the Southern Alps-Bakony and Buda mountains-Eastern Bükk Mountains-Dinarides region. The Middle Triassic-Middle Jurassic ultramafic-mafic igneous rocks of the Gemer-Bükk subunit can be correlated with the ophiolites of the Inner Dinarides. Geochemistry of the mafic rocks is consistent with an origin from an N-MORB and E-MORB source mantle. The Middle to Late Triassic ultramafic and mafic rocks of the Bódva and Darnó-Szarvaskö series could have originated along the mid-oceanic ridge system of the northwestern segment of the Vardar ocean (Meliaticum). The Middle Jurassic igneous rocks of the Darno-Szarvasko series could have corresponded to the opening of a back-arc basin. Early Cretaceous alkaline volcanic rocks of the Mecsek-Alföld zone in the Tisza block formed as a result of continental rifting along the southern margin of the European plate. Two volcanic series-a mafic and a sodic group-were generated from an OIB-like asthenospheric mantle. Separation of the Tisza block from the European plate occurred contemporaneously with volcanic activity during the late Early Cretaceous.