Zirconology of syenites of the Northern Timan

Northern Timan is an uplifted block of the Upper Precambrian basement of the Timan Ridge, where intrusive rocks of various compositions cut Neoproterozoic metaterrigenous rocks of the Barmin Group and are overlain by Lower Silurian limestone. Syenites are widespread in the Cape Bolshoy Rumyanichny pluton and compose the Krayny Kameshek and Malyi Kameshek plutons. To determine the age of the syenites, U—Pb dating of zircons was carried out using secondary ion mass spectrometry (SIMS). The age of zircons from syenite of the Cape Bolshoy Rumyanichny pluton is 613 ± 7 Ma, Krayny Kameshek pluton — 602 ± 5 Ma, and Malyi Kameshek pluton — 598 ± 17 Ma. Similar zircon ages are known for other alkaline igneous rocks that occur within the Cape Bolshoy Rumyanichny pluton: olivine-kersutite gabbro — 614 ± 2 Ma, granites — 614 ± 11 Ma. Zircons from subalkaline granites of the Bolshoy Kameshek pluton are of the same age — 613 ± 6 Ma. The location of the plutons in the area of the Late Riphean passive margin of Baltica, the close association of subalkaline and alkaline granites, syenites, and alkaline gabbros indicate the anorogenic nature of these magmatic rocks and possible relationship with mantle plume activity. Ediacaran magmatic rocks of 614—600 Ma located in the Northern Timan could be associated with the final stages of Rodinia breakup, accompanied by plume-related magmatism, the products of which are also known in the eastern part of Laurentia and in the Scandinavia.