New Data on the Age (SHRIMP II) of Protolith and Paleoproterozoic Transformations of the Archean Keivy Terrain (Kola Peninsula)

摘要

The Keivy terrain is a unique structure principally different from adjacent territories. It comprises four complexes of magmatic and supracrustal rocks: the supposed basement composed of the tonalite-trondhjemite association (TTG), the Lebyazhinskaya Series of acid and intermediate metavolcanic rocks, the Keivy Series of high-aluminum schists [ 1 ], and the complex of alkaline granites, sometimes associating with ultrabasic and alkaline rocks [2]. The tectonic boundaries of the terrain control the location of basic and utrabasic intrusions including the layered plutons of the Panskaya and Fedorovskaya tundra. Of special importance for the solution of the problems of peri-odization of endogenous problems are the studies in which the U-Pb study of zircons provided the Neoarchean age of metavolcanic rocks of the Lebyazhinskaya Series (2750 Ma) [3], alkaline granites and granosyenites of the western part of the Keivy terrain (2630-2674 Ma) [4, 5], and plutons of the Panskaya and Fedorovskaya tundra (2500 Ma) [6]. This demonstrates that the considered structure is not only entirely composed of Archean formations, but its separation took place at the end of the Neoarchean. This study was aimed at local U-Pb (SHRIMP) dating of the processes of Paleoproterozoic tectonic and meta-morphic transformation of Archean structures within the considered terrain.