Sheeted Intrusions in the Svecokarelides of the Ladoga Region: Structural Control, Petrogenesis, Geochemical Analysis of Rocks, and Geodynamic Setting

The article characterizes in detail the specific morphological type of the system of metaintrusive sheeted bodies that constitute a single differentiated gabbro–diorite–granodiorite–granite series of the Serdobol Complex in the structure of the Svecokarelides of the southeastern Baltic Shield. It is shown that they belong to the transpressive nappe-thrust paragenesis of the Meyeri suture zone separating the metaterrigenous formations of the Karelides and Svecofennides at the pericratonic margin of the Archean Karelian Craton. These formations fill syndeformational near-fault fractures and, in addition, they may be feeding channels for syntectonic plutons of the early Svecofennian tectogenesis. Based on petrochemical analysis their formation attributed to the complexes of tonalite–trondhjemite–granodiorite series (TTG) and adakite-like rocks that formed in the accretionary–collisional system of the interaction zone of the Archean continental plate and Svecofennian juvenile oceanic crust is determined. The Sm‒Nd isotopic dates of this magmatic series and the host rocks of the Ladoga metaterrigenous complex are presented. The article discusses the peculiarities of their mineral and chemical composition, as well as relicts of xenogenic zircon close in age detected in the magmatic substrate. The study reveals the significant influence of partial melting processes in the Archean basement‒Paleoproterozoic cover system on the formation of rocks of the Serdobol Complex, presumably initiated by the influx of melts from the subducting slab. The processes of crustal contamination of initial magmas are considered.