U–Pb and Sm–Nd isotopic constraints on the evolution of the Paleoproterozoic Peräpohja Belt, northern Finland

• A new event of granitic plutonism in northern Finland at 1.98 Ga was identified.
• Kalevian rocks in the Peräpohja Belt shows ca. 1.91 Ga detrital zircon population.
• Two studied quartzitic units can be correlated with each other.

Ten localities, representing metasedimentary and igneous rocks from the northern part of the Paleoproterozoic Peräpohja Belt, Fennoscandian Shield, were sampled for zircon U–Pb dating by LA-MC-ICP-MS and Sm–Nd analysis by TIMS. The results revealed two phases of granitic magmatism that took place at 1.99 Ga and 1.79–1.77 Ga. The former age (1989 ± 6 Ma) was given by the Kierovaara granite pluton representing the first example of felsic plutonism of this age in northern Finland, though A-type felsic volcanic rocks of the same age have previously been recognized. The strongly negative initial ɛnd values obtained for granitoids, ranging from −3.9 to −11.4, are compatible with the previous Sm–Nd data, indicating the presence of Archean basement in northern Finland at the time of granite emplacement. A garnet-whole rock Sm–Nd age of 1752 ± 14 Ma was measured for a mica gneiss, constraining the time of metamorphic cooling down to the closure temperature of garnet.Detrital zircon grains from quartzite samples belonging to the Jatulian Palokivalo Formation and a stratigraphically unassigned lithodemic unit, the Mellajoki Suite, yielded solely Archean zircon populations. In contrast, our sample from the Martimo Formation representing Kalevian sedimentation revealed a 66% Paleoproterozoic detrital zircon component with the youngest zircon grains showing an age of ca. 1.91 Ga. The new age data allow us to constrain the depositional time of this sedimentary unit between ca. 1.91 and 1.88 Ga, the latter being the time of the synorogenic plutonism. Our geochronological data coupled with recent data from other Karelian belts suggest that the depositional time period for rocks assigned to the Kaleva spans ca. 150 Ma and the simple division of these rocks into two non-coeval units, the Lower and Upper Kaleva, has become problematic.