The Precambrian of Gotland, a key for understanding the Proterozoic evolution in southern Fennoscandia

Sundblad, Krister; Salin, Evgenia; Claesson, Stefan; Gyllencreutz, Richard; Billström, Kjell

doi:10.1016/j.precamres.2021.106321

Cited by 5 publications

(1 citation statement)

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“…Malbork IG1 (1499 Ma) and Kościerzyna IG1 (1499-1502 Ma)) in the vicinity of the Baltic Sea (Fig. 1B; Krzemińska et al 2017 and slightly younger than 1525-1499 Ma A-type rocks of the MC (Dörr et al 2002;Wiszniewska and Krzemińska 2021), as well as the prominent (1585 Ma) Riga batholith (Rämö et al 1996) with its part in Gotland (Sundblad et al 2021). Numerous small intrusive bodies and large batholiths of A-type granite composition are Rämö et al 1996 [Riga, Märjamaa, Naissaare], Neymark et al 1994 [Salmi], Rämö et al 2014;Heinonen et al 2010a [Wiborg], Fröjdö et al 1996 [Nordingrå], Heinonen et al 2010a [Eurajoki, Kolinummi], Rämö 1991 [Åland], Heinonen et al 2010b [Ahvenisto], Andersson et al 2001 [Rödön, Nordsjö] Table 4 Regional compilation of ages of AMCG massifs in Fennoscandia well documented in southern Fennoscandia.…”

Section: Regional Contextmentioning

confidence: 96%

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

et al. 2023

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Rapakivi-type quartz monzonite and the underlying dark-grey granodiorite from the Pietkowo IG1 borehole, in the Polish part of southernmost Fennoscandia have been investigated using whole-rock geochemistry, Sm–Nd isotope geochemistry and U–Pb zircon dating. The quartz monzonite was emplaced at 1495–1491 Ma, although slightly older zircon cores (antecrysts) of 1513 Ma imply a two-stage crystallization. The geochemical similarities with Mazury Complex granitoids, their metaluminous and alkali-calcic nature, elevated contents of F, Ga and high-field-strength-elements (HFSE), indicate that the Pietkowo IG1 rapakivi-type quartz monzonite is an ‘A-type’ granitoid. The presence of magnetite and titanite indicates crystallization under oxidizing conditions. The rock is classified as A2 sub-type, and the Nb/Y ratio implies a within-plate setting. The dark-grey granodiorite, dated to 1813 Ma, has a calc-alkaline character, typical of a volcanic-arc environment. Initial whole rock εNd values range between -2.9 and -3.3 for the rapakivi-type quartz monzonite and from -1.0 to + 1.1 for the dark-grey granodiorite. We suggest that the A-type Pietkowo IG1 rapakivi-type quartz monzonite was generated from the dark-grey granodiorite via partial melting at middle to lower crustal levels. The most plausible ascent route for the quartz monzonite was via lithospheric-scale weakness zones, between the eastern margin of the Mazowsze Domain and Belarus-Podlasie Granulite Belt, i.e., the Białystok fault. Therefore, the Pietkowo IG1 rapakivi-type quartz monzonite is a representative of the Mesoproterozoic A-type granitoid occurrence in southernmost Fennoscandia.

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