Vendian – Early Cambrian granites of the Krutorechensky complex (Northern Urals, Russia): protolith age, geodynamic conditions of generation and transformation

The Main Uralian fault (MUF) zone is a suture at the junction of the Urals and the East European platform (EEP). Its complex tectonic melange is still poorly studied. We obtained new data on compositions and ages of the Krutorechensky granites (KG) composing an intensely tectonized and boudinaged elongated body discovered in meta‐ terrigenous and meta‐volcanogenic rocks in the western part of the MUF zone. In chemical composition, these gra‐ nites are similar to the Vendian‐Cambrian collisional granitoids of the Isherim and Lyapin blocks. The LA‐ICP‐MS method was used to determine U‐Pb zircon ages for the KG samples. The zircons contain ancient xenogenic cores (1221–1034 Ma) and young rims (400±6 Ma). The Middle Riphean ages of zircons from the protolith suggest that the KG block (belonging to the Prisalatim zone and located west of the MUF zone) is a fragment of the EEP, because the complexes of the Ordovician‐Devonian Tagil paleo‐island arc (located further eastward) are mostly dated to the Ven‐ dian. The KG crystallization age (537±2 Ma) is practically the first (Vendian) early Cambrian dating for the granites sampled in the MUF zone. Considering this age and the petrogeochemical features, there are grounds to suggest that the Krutorechensky granites originated due to tectonic‐magmatic events (with possible pluming) that took place at the final stage of the Timan collision, similar to granites of the western slope of the Northern Urals (Moiva, Posmak and Velsov massifs). Subsequently, these granites were involved in the Paleozoic accretion‐collision processes that created the modern MUF zone (i.e. tectonic melange). Our study results are important for clarifying the structure of the Urals‐EEP junction zone and useful for geological mapping and metallogenic assessment of the region.

Main Uralian fault (MUF), accretion, granite, zircon, Vendian, Cambrian, Timan collision

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