Long-lived LREE mobility in the cratonic, rift and foredeep to foreland sedimentary cover at the western margin of the Karelia Province

We propose that alkali-bearing oxidizing fluids started to form in the cratonic sequences due to diagenetic reactions maybe as early as 2.3-2.1 Ga. Alkalinity of fluids was later increased by interaction with alkaline 2.05 Ga source materials before and during the c. 1.91-1.92 Ga foredeep to foreland basin stage. Basin inversion and metamorphic crystallization occurred at 1.91-1.87 Ga. Episodes of fluid migration at 1.78-1.73 Ga and afterwards were focused along fracture zones and in microfracture networks. The 0.4 Ga stage is the most prominent of the < 1.7 Ga events and is best explained by assuming shield-scale foreland basin related to the Caledonian orogenic front, causing heat redistribution and also fluid circulation in the underlying crystalline basement. The 2.1 Ga formed marginal fault has been a very important shield-scale tectonic element and a pathway for fluid circulation for almost 2 billion years.