The crustal structure of Onega-Kandalaksha paleorift identified by complex analysis of the anomalous magnetic field of the White Sea

Geological and geophysical studies recently conducted in the White Sea and the adjacent territory have provided new data on the deep structure of this region. Our study aims to conduct complex analysis of the anomalous magnetic field and the geological and geophysical data on the Onega-Kandalaksha paleorift located in the White Sea basin and the adjacent southeastern land area, and to develop a model showing its deep structure. The basis for analysing the magnetic field is the anomalous magnetic field (AMF) map constructed by the authors using the magnetic survey data consolidated by the Marine Arctic Geological Expedition (MAGE) in 2003–2008 and supplemented by the survey data of the Institute of Oceanology RAS in 2001–2004. The parameters of the magnetically active layer are estimated by the independent complementary methods of quantitative interpretation developed by the Laboratory of Geophysical Fields, P.P. Shirshov Institute of Oceanology RAS. This article describes a model showing the structure and formation of the magnetically active layer of the White Sea paleorift. Our study shows that the magnetically active layer of the paleorift system has a complex structure reflecting all the main stages in the evolution of tectonic activity in the White Sea region, from the Middle and Late Riphean to the last glaciation of the Quaternary period. The model includes three structural layers, each corresponding to a certain stage. The bottom structural layer is the base of the magnetically active layer, which reflects the continental rifting stage in the evolution of the White Sea mobile belt in the Middle and Late Riphean. The middle structural layer reflects the Middle Paleozoic (Late Devonian) stage of rifting reactivation, which is characterized by alkaline-ultrabasic magmatism and represented by swarms of alkaline dykes and diatremes, including kimberlite pipes. The top structural layer reflecting a high-frequency component of the AMF is related to the highly magnetic sources of anomalies located in the upper part of this structural layer. The characteristics of the top structural layer suggest that it formed in the Late Pleistocene – Holocene and developed during the final stage the tectonic activation of this region. The deep crustal structure of the White Sea basin is specified in our model showing the magnetically active layer for the low-frequency component of the AMF. In the southeastern part of the basin, magmatism products of the basic (Riphean – Vendian) and alkaline-ultrabasic (Middle Paleozoic) composition are abundant in the crust and provide for a strong magnetic source of anomalies, the lower edges of which are traced at the depths to 30 km. This probably reflects the most active plume-lithospheric interaction. Wedging and uplifting of the magnetically active layer northwestward along the Onega-Kandalaksha rift is related to the White Sea (Belomorsky) deep fault. This fault is a long-lived conduit that channels magma from the central portion of the plume, as evidenced by the igneous bodies of the basic composition in the basement and central parts of the sedimentary wedge in the Kandalaksha graben. The complex analysis of the AMF in the White Sea region suggests the presence of morphologically different igneous bodies in the upper crust in the study region.

1. Aplonov S.V., Fedorov D.L. (Eds.), 2006. Geodynamics and Possible Oil and Gas Potential of the Mezensk Sedimentary Basin. Nauka, Saint Petersburg, 319 p. (in Russian)

2. Baluev A.S. (Ed.), 2012. Tectonic Map of the White Sea and Adjacent Territories. Scale 1:500000. IPP Kuna, Moscow (in Russian)

3. Baluev A.S., Przhiyalgovskii E.S., Terekhov E.N., 2009a. New data on tectonics of Onega-Kandalaksha paleorift (the White Sea). Doklady Earth Sciences 425 (2), 249–252. https://doi.org/10.1134/S1028334X09020160.

4. Baluev A.S., Zhuravlev V.A., Przhiyalgovskii E.S., 2009b. New data on structure of the central part of the White Sea paleorift system. Doklady Earth Sciences 427A (6), 891–896. https://doi.org/10.1134/S1028334X09060014.

5. Baluev A.S., Zhuravlev V.A., Terekhov E.N., Prahiyalgovsky E.S., 2012. Tectonics of the White Sea and Adjacent Areas. The Explanatory Notes to “The Tectonic Map of the White Sea and Adjacent Areas”, at a Scale of 1:1500000. GEOS, Moscow, 104 p. (in Russian)

6. Brusilovskii Yu.V., Ivanenko A.N., Popov K.V., Filin A.M., 2003. Geomagnetic survey in the White Sea. Oceanology 43 (2), 258–262.

7. Brusilovsky Yu.V., Bush V.A., 2015. A model of the magnetically active layer of Western Mezen syneclise. Geophysical Research 16 (1), 69–76 (in Russian)

8. Bush V.A., Kalmykov B.A., 2015. New data on Pre-mezozoic intraplate magmatism in the East European platform. Geotectonics 49 (5), 395–410. https://doi.org/10.1134/S0016852115050027.

9. Cooper G.R.J., 1997. Forward modelling of magnetic data. Computers & Geosciences 23 (10), 1125–1129. https://doi.org/10.1016/S0098-3004(97)00099-X.

10. Dobrynina M.I., 1992. Riftogenesis in the Precambrian geological history of the northern regions of the USSR. In: F.P. Mitrofanov, V.I. Bolotov (Eds.), Deep structure and geodynamics of crystalline shields of the European part of the USSR. Publishing House of KSC RAS, Apatity, p. 71–78 (in Russian)

11. Gafarov R.A., 1963. The Structure of the Precambrian Basement of the Northern Region of the Russian Plate. Publishing House of the USSR Acad. Sci., Moscow, 212 p. (in Russian)

12. Ivanenko A.N., Brusilovskiy Yu.V., Filin A.M., Shishkina N.A., 2012. Methods of processing and interpretation of marine magnetic data in the works on oil and gas fields in shallow water. Geofizika (The Russian Geophysics Journal) (3), 60–70 (in Russian)

13. Kazanin G.S., Zhuravlev V.A., Pavlov S.P., 2006. Structure of the sedimentary cover and petroleum capacities of the White Sea. Burenie i Neft (Drilling and Oil) (2), 26–28 (in Russian)

14. Kharitonov L.Ya., 1955. The main features of the stratigraphy and tectonics of the eastern regions of the Baltic Shield. In: Proceedings of the 3rd session of the Commission for determining the absolute ages of geological formations. Publishing House of the USSR Acad. Sci., Moscow, p. 51–77 (in Russian)

15. Konstantinovsky A.A., 1977. Riphean Onega-Kandalaksha graben of the East European platform. Geotektonika (Geotectonics) (3), 38–45 (in Russian)

16. Last B.J., Kubik K., 1983. Compact gravity inversion. Geophysics 48 (6), 713–721. https://doi.org/10.1190/1.1441501.

17. Portniaguine O., Zhdanov M.S., 1999. Focusing geophysical inversion images. Geophysics 64 (3), 874–887. https://doi.org/10.1190/1.1444596.

18. Valeev R.N., 1978. Aulacogenes of the East European Platform. Nedra, Msocow, 152 p. (in Russian)

19. Zander V.N., 1972. Geological Structure and Ore-Bearing Capacities of the Basement of the Baltic Shield Slopes. Nedra, Leningrad, 152 p. (in Russian)

20. Zander V.N., Tomashunas Yu.I., Berkovsky A.N., Suvorova L.V., Dedeev V.A., Kratts K.O., 1967. Geological Structure of the Basement of the Russian Plate. Nedra, Leningrad, 124 p. (in Russian)

21. Zhuravlev V.A., 2007. The crustal structure of the White Sea region. Razvedka i Okhrana Nedr (Exploration and Protection of Mineral Resources) (9), 22–26 (in Russian).

22. Zhuravlev V.A., Pavlov S.P., Shipilov E.V., 2007. The structure of the basement and the sedimentary cover of the White Sea sector of the East European Platform. In: G.G. Matishov (Ed.), Complex studies of the processes, Characteristics and resources of the Russian seas of the North European basin (Project of the Studies of Nature of the World Ocean Sub-Programme in the World Ocean Federal Programme). Vol. 2. Publishing House of KSC RAS, Apatity, p. 302–310 (in Russian)