Age and formation conditions of granitoids of the Maldinsky massif in relation to the typification of granitoids of the Lyapinsky anticlinorium (Subpolar and Northern Urals)

This paper substantiates the proposition that granite formation processes in the Subpolar-Northern Urals segment of the Earth’s crust, represented in its modern structure by the Lyapinsky anticlinorium, occurred over a long period, beginning at least from the end of the Early Proterozoic to the Early Paleozoic, but developed discretely with a long hiatus spanning a significant portion of the Riphean period. It is shown that the Salnero-Manhambo Complex (SMC), which, according to some researchers, encompasses all manifestations of granitoid magmatism in the Lyapinsky anticlinorium, should include only Late Vendian-Early Cambrian granitoids formed during the collisional and post-collisional stages of Timanian tectogenesis. The morphological features, composition, and U-Pb (LA-SF-ICP-MS) isotopic age of accessory zircon in granites of the Maldinsky massif, identified as a petrotype of the SMC first-phase granitoids, have been established. The age of zircon grains from the main population is 555±2 Ma, interpreted as the time of rock formation. The presence of ancient cores (over a billion years old) in zircon crystals is associated with contamination of the host rocks during the early stage of melt crystallisation.