Search

Results:

Vol. 28 (2025 year), No. 1, DOI: 10.21443/1560-9278-2025-28-1

Kozlov N. E., Sorokhtin N. O., Mudruk S. V.
Correlation of the supracrustal complexes of the Small and Large Keivy, North-East of the Baltic Shield

The issue of correlation between the Small and Large Keivy sections is considered using a technique that includes searching for trends in partially ordered sets of random variables and assessing the degree of similarity/difference between rock compositions. The lower part of the section (Chervurt formations) of the Keivy structure was formed as a result of rewashing and redeposition of the substance of the structure itself. The formation of the Large Keivy section continued in the same regime with the formation of the Vykhchurt subsuites. With the activation of the tectonic regime, the Pestsovtundra suite, which completes the Large Keivy section, was formed due to the substance of the underlying Chervurt complexes and framing rocks (primarily the rocks of the Murmansk block). The formation of the Small Keivy section at the same stage occurred in a different way. With the activation of the tectonic regime, less than that which accompanied the formation of the Pestsovtundra complexes of the Large Keivy, the deposition of the Snezhnoborsky complexes began. The Upper Chervurt formations participated to a significant extent in their formation, but the products of the destruction of the framing rocks (primarily the Murmansk domain) were a noticeable addition. At this point, the formation of the Keivy sections was completed. The described difference in the processes that accompanied the accumulation of sediments in the Large and Small Keivy sections is explained by the differences in the position of these areas within the paleobasin of the Keivy time.

(in Russian, стр.7, fig. 2, tables. 4, ref 11, AdobePDF, AdobePDF 0 Kb)

Vol. 29 (2026 year), No. 1, DOI: 10.21443/1560-9278-2026-29-1

Kozlov N. E., Mudruk S. V., Sorokhtin N. O.
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.

(in Russian, стр.12, fig. 4, tables. 3, ref 20, AdobePDF, AdobePDF 0 Kb)