Charnockitic rocks in the crystalline basement of Western Lithuania: implications on their origin and correlation with the Askersund suite in SE Sweden

Abstract

The polyphase Kuriai batholith of charnockitic rocks, extending over some 10 000 km2 with a few smaller plutons, has been revealed in the West Lithuanian Granulite Domain. Plutons intruded between 1850 and 1815 Ma, and are composed of intermediate and acid varieties of charnockitic rocks. They are ferroan, calc-alkalic to alkali-calcic, predominantly peraluminous, and reveal both S- and A-type granite characteristics. Based on petrochemical data charnockitic magma was generated in the continental crust more then 30 km-thick, that formed in a subduction-related collisional tectonic environment. Magmatism took place in the later orogenesis period, transitional from syn-kinematic collisional to post-kinematic extensional phases. Magma generation was presumably triggered by intrusions of basalt magma in the crust. The rock composition was determined by the interaction of basaltic magmas with anatectic melt of Al-rich metasedimentary rocks, involving mechanisms of assimilation and hybridization. The close geochemical affinity of the Kuriai suite in Western Lithuania to the coeval Askersund plutonic suite in southeastern Sweden implies a similar tectonic environment and processes of the formation of continental crust and suggests possibilities of wider correlation between these regions