Вестник МГТУ. 2020, Т. 23, № 1.

In addition to the volcano-sedimentary rock units, alkaline granites are also common in the domain. The emplacement age of these granites is estimated to vary within 2,630-2,760 Ma (Батиева, 1976; Bayanova et al., 1998). The zircon age for the porphyroblastic granites of the Kolovaysky massif cutting through the rocks of the Lebyazhinskaya Series is found to be 2,620±30 Ma (Пушкарев, 1990). The syntectonic grabbro-anorthosites intruded near the contact zone between the Upper-Ponoy block and Keivy domain 2,760±80 ( Composition..., 2008) or 2,659±3 million years ago (Bayanova et al., 1998). The geodynamic and petrogeochemical studies executed within the Keivy microcontinent have demonstrated that it was buried at some depth in Late Archean by the adjacent overthrusted continental-crust domains of the Kola region. As a result, the Keivy microcontinent may be considered as the oldest median massif of the continental crust within the worldwide Late Archean collision areas (Fig. 2). Fig. 2. Peculiar features of the Keivy median massif formation in the late Archean: 1 - water basin; 2 - sedimentary cover of the Keivy median massif; 3 - sedimentary cover of adjacent terrains and microcontinents; 4 - continental crust; 5 - folds of the greenstone type; 6 - synorogenic tonalite-trondhjemites, granodiorites, migmatite granites, and remobilized crust of the Keivy median massif; 7 - subcrustal mantle; 8 - direction of collisional thrusting of microcontinents and terrains over the Keivy median massif; 9 - section line; 10 - contemporary level of the erosional truncation (Козлов и др., 2019) Рис. 2. Закономерности формирования Кейвского срединного массива в позднем архее: 1 - водный бассейн; 2 - осадочный чехол Кейвского срединного массива; 3 - осадочный чехол сопредельных террейнов и микроконтинентов; 4 - континентальная кора; 5 - складчатые образования зеленокаменного типа; 6 - синорогенные тоналит-трондьемиты, гранодиориты, мигматит граниты и ремобилизованная кора Кейвского срединного массива; 7 - подкоровая мантия; 8 - направление коллизионного надвигания микроконтинентов и террейнов на Кейвский срединный массив; 9 - линия разреза; 10 - современный уровень эрозионного среза (Козлов и др., 2019) For example, the South-Chinese and Chinese-Korean lithospheric plates may be regarded as younger analogues to this type of geological structures. In accordance with available geological and geophysical data, the dip azimuths of all domain borders are oriented towards its junction with other crust areas; the domain itself has a shape of a truncated pyramid. Materials and methods This research attempts to find compositional features of supracrustal rock units that argue for or against the above geodynamic reconstructions at a substance level. It is based on an assumption that, within a proposed emplacement model for the Keivy rock units, its various areas should have been compositionally similar to the substance of adjacent domains to a different extent. Its northern part should have demonstrated a more significant similarity with the Murmansk domain rocks than the southern one. The latter, on the contrary, should have been closer to the Tersky domain and White Sea mobile belt rock assemblages than the northern one. The resemblance between the western and eastern parts of the Keivy and Kola-Norwegian blocks should have manifested in a similar way (Fig. 1-3). Due to the absence of necessary data on the rock composition of the Chapoma and East-Kola terrains, possible similarity or difference from the rocks of the eastern and southeastern frame of the Keivy domain has not been studied. This task was solved using a method for the identification of affinity between the study objects on the basis of selecting homogenous groups (Kozlov et al., 2018), and namely, between the rock assemblages of the