Metamorphic petrology and geochemistry of the Sarkadkeresztúr Basement-High with special regard to orthogneiss (Tisza Mega-unit, SE Hungary)

Core samples of metamorphic rocks from the Sarkadkeresztur Basement High (Bekes-Codru Unit, Tisza Mega-unit) were examined, consisting mainly of two-feldspar augengneiss, garnet-andalusite-staurolite-bearing micaschist and paragneiss. The protolith of the plagioclase-microcline-augengneiss was found to be S-type granite (syenogranite) of unknown age. According to the major element analyses the protoliths of the studied metagranitoids of this basement can be classified as a syenogranite of metaluminous and peraluminous character displaying subalkaline affinity and a calcic granitic composition. The REE patterns are characterized by a slight enrichment of the light REEs and negative Eu and Yb anomalies. On the basis of discrimination diagrams for major and trace elements, the studied rocks were formed in a syn-collisional (continent-continent collision zone) tectonic environment. The low-pressure amphibolite facies metamorphism, which affected this basement, can be assigned to the Variscan.