New approaches to lithological and stratigraphic research and mapping of the early Precambrian complexes (using an example of the Paleoproterozoic and Archean structures of Keivy, Kola Peninsula)

Previously, the team of authors proposed a new method for the comparative analysis of geological objects. Its foundation is an assessment of the proximity of statistically significant petrogeochemical characteristics. The key advantage of this approach is the ability to quantitatively determine the degree of similarity for heterogeneous samples, which favorably distinguishes it from many classical geochemical methods. The successful application of the technique for comparing geological objects has allowed its adaptation for solving lithological-stratigraphic tasks in complexly structured Early Precambrian complexes, where traditional methods often prove insufficiently effective. In the present work, the method has been tested on supracrustal formations of the Keivy Domain. At the first stage, it was used for the correlation of Paleoproterozoic strata. The results confirmed existing stratigraphic schemes: Serpovidny complex Formation (Pestsovokeivskaya Formation, Serpovidny Ridge area) demonstrates the greatest similarity with formations of the Umba (Imandra-Varzuga Belt) and Kuetsyarvi Formations (Pechenga Structure). At the next stage, the method was applied to older complexes, the correlation of which had previously been problematic. The research has established that the deposits of the upper part of the Lebyazhinskaya Formation and the Chervurta Subformations were formed throughout the entire Keivy structure primarily due to the reworking and redeposition of underlying rocks. The analysis has also revealed differences in the geological history of the two main regional structures – the Bolshie and Malye Keivy. The formation of strata within them occurred in different settings. In the Bolshie Keivy, stable sedimentation conditions persisted until the accumulation of the Vykhchurta Formation. Active tectonic reorganization began later, during the formation of the Peschtsovotundrovsky complexes, when clastic material from the surrounding areas, primarily from the Murmansk Domain, began to enter the sedimentary basin. In the Malye Keivy, this activation occurred earlier, as recorded in the composition of the rocks of the Snezhnoborskaya Formation. The reconstruction of the geological history of the Keivy Domain, proposed based on petrogeochemical correlation, offers a solution to previously existing contradictions in correlating the supracrustal complexes of the Bolshie and Malye Keivy.