A new A-type granitoid occurrence in southernmost Fennoscandia: geochemistry, age and origin of rapakivi-type quartz monzonite from the Pietkowo IG1 borehole, NE Poland

Abstract Rapakivi-type quartz monzonite and the underlying dark-grey granodiorite from Pietkowo IG1 borehole, in Polish part of southernmost Fennoscandia have been investigated using whole-rock geochemistry, Sm–Nd isotope geochemistry U–Pb zircon dating. The was emplaced at 1495–1491 Ma, although slightly older cores (antecrysts) 1513 Ma imply a two-stage crystallization. geochemical similarities with Mazury Complex granitoids, their metaluminous alkali-calcic nature, elevated contents F, Ga high-field-strength-elements (HFSE), indicate that rapakivi-type is an ‘A-type’ granitoid. presence magnetite titanite indicates crystallization under oxidizing conditions. rock classified as A 2 sub-type, Nb/Y ratio implies within-plate setting. granodiorite, dated to 1813 has calc-alkaline character, typical volcanic-arc environment. Initial whole ε Nd values range between -2.9 -3.3 for -1.0 + 1.1 granodiorite. We suggest A-type generated via partial melting middle lower crustal levels. most plausible ascent route lithospheric-scale weakness zones, eastern margin Mazowsze Domain Belarus-Podlasie Granulite Belt, i.e., Białystok fault. Therefore, representative Mesoproterozoic granitoid occurrence Fennoscandia.