Paleoproterozoic mafic dyke swarms of the Belomorian Province, eastern Fennoscandian Shield

Abstract

Paleoproterozoic mafic igneous rocks (2450–1970 Ma) are exposed in the form of layered intrusions, dykes, and volcanic rocks in the Karelian, Kola and Murmansk provinces and in the form of dykes and small intrusions in the Belomorian Province, Eastern Fennoscandian Shield. The age and sequence of mafic dyke emplacement during the Paleoproterozoic are very similar in these regions. Further comparisons of geochemical characteristics of mafic dyke swarms in the Belomorian Province and neighboring cratons show considerable similarities. At least three distinct groups of Paleoproterozoic mafic dykes exist in the Belomorian Province of the Eastern Fennoscandian Shield. They are (i) early Mg-tholeiitic dykes, (ii) ca. 2.44–2.36 Ga high-Mg gabbronorites and (iii) ca. 2.12 Fe-tholeiitic dykes. Research into mafic dykes of the Belomorian Province and their comparison with Paleoproterozoic dyke swarms of the Karelian, Kola and Murmansk provinces has provided evidence for at least two extensive shared magmatic events dated to ca. 2.5–2.4 Ga and ca. 2.1 Ga in the Paleoproterozoic in the Eastern Fennoscandian Shield confirming that the Belomorian Province does not represent a Paleoproterozoic suture but rather a deep-eroded inner part of the Lapland-Kola orogen foreland.