The Ďumbier – Prašivá high K calc-alkaline granite suite (Low Tatra Mts., Western Carpathians): Insights into their evolution from geochemistry and geochronology

Abstract

The geochemistry of major Low Tatra granitic types, namely Prašivá porphyritic Bt (biotite)-granodiorite and Ďumbier Bt-tonalite, indicate their derivation from initial hybrid magmas and represent a mixture among several magma pulses formed via melting of the heterogeneous lower crust. The high K calc-alkaline peraluminous character, along with high Ba, Sr + LREE contents correspond to the partial melting of K-rich mafic and the intermediate hydrated lower crustal source in equilibrium with amphibole or possibly garnet with variable involvement of metasedimentary and/or felsic metaigneous sources. The zircon isotopic age of 360.4 ± 2.7 Ma recorded from diatexite reflects the timing of hightemperature metamorphism of subducted continental crust, and thus corresponds in an initial anatectic process within the present Tatric Unit. The magmatic ages are in the largely overlapping sequence of 353 ± 2 Ma for the Ďumbier tonalite and 352 ± 3 Ma and 351.9 ± 2.9 Ma for Prašivá Aln (allanite bearing)-subtype and Mnz (monazite bearing)-subtypes, which indicate successive multiple emplacement of magma batches and natural evolution towards their more crustal character. Magmatism in the Low Tatra Mts. represents a post-collisional plutonic system related to the slab break-off mechanism described in the close Malá Fatra crystalline basement as well. Heat from mantle upwelling and volatiles from previous subduction forced the melting of the lower crust towards K-rich mafic or intermediate lithologies, as well as during the emplacement of long-lasting melting of felsic metasedimentary crustal sources. The crystalline core of the Low Tatra Mts. is another example of composite granite pluton in the Western Carpathians, which represents a product of the multiphase Late-Variscan post-collisional setting.