Russian Journal of Earth Sciences Russian Journal of Earth Sciences Russian Journal of Earth Sciences 1681-1208 47023 ОРИГИНАЛЬНЫЕ СТАТЬИ ORIGINAL ARTICLES ОРИГИНАЛЬНЫЕ СТАТЬИ Continuous record of geomagnetic field variations during cooling of the Monchegorsk, Kivakka and Bushveld Early Proterozoic layered intrusions Continuous record of geomagnetic field variations during cooling of the Monchegorsk, Kivakka and Bushveld Early Proterozoic layered intrusions Pechersky D M Pechersky D M Zakharov V S Zakharov V S Lyubushin A A Lyubushin A A Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ru Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ru Moscow State University, Moscow, Russia ru Moscow State University, Moscow, Russia ru Institute of Physics of the Earth, Russian Academy of Sciences,Moscow, Russia ru Institute of Physics of the Earth, Russian Academy of Sciences,Moscow, Russia ru 6 6 391 456 10 11 2021 https://ras.editorum.ru/en/nauka/article/47023/view

A continuous record of the geomagnetic field direction during of cooling of the Monchegorsk 2.5Ga, Kivakka 2.45Ga and Bushveld 2.06Ga layered intrusions was conducted for the first time. The low-Ti titanomagnetites Tc = 530-580o C are the main natural remanent magnetization NRM carriers. The high temperature NRM component according to petromagnetic characteristics is thermoremanent and was acquired at the cooling phase of the intrusion. The magnetic grains above 540o C are close to a single-domain state. The temperature versus time and cooling velocity versus temperature and time dependences during cooling of intrusions were calculated on the basis of solution of the Stefan problem and the nonstationary heat conduction problem. The geothermal gradient value was taken as 20okm-1. The unblocking temperatures in the course of thermal demagnetization of samples Td and the blocking temperatures during cooling from high temperatures Tb rate dependences were used for conversion of the Td to Tb Dodson and McClelland, 1980. A detailed thermal demagnetization at 2o-3o interval from 530oC up to 580oC was made and a pattern of behavior of the geomagnetic field direction was obtained afor the time of "running'' the Curie points over the section and bfor the cooling time of the intrusion at each sampling point from Tb = 580oC. A wavelet analysis has been used to study the field variation etc. The main rhythms of the direction variation spectrum are 3-4.5, 5-7, 8-10, 12, 15-17, 19-20, 30-40, 50-60, and 90-100kyr and they change in time. The length of rhythms is different and ranges from 1-2 oscillations "splashes'' up to 10-12. The Monchegorsk intrusion. The pole 265.3o E, 1.3o N. The length of record is ~70kyr. The geomagnetic excursion of the reversal polarity lasting for less than 2000 years and the R-subchron of ~60kyr were recorded. Kivakka intrusion. The A1 prefolded and A2 synfolded components which occurred at the stage of cooling of the intrusion are isolated. The body started to tilt approximately 85kyr after intrusion emplacement and it lasted for 20-25kyr. The pole of the A1 is 17.8oS and 247oE. Duration of the record is 35kyr and only one R-polarity existed during this period. Bushveld intrusion. Orientation of the horizontal plane of the samples has been restored from viscous magnetization and a paleomagnetic pole 12oN, 35.4oE has been determined from a high-temperature N-component of the NRM. A paleomagnetic record for ~500kyr was obtained; polarity of the field has changed only once during this period.

A continuous record of the geomagnetic field direction during of cooling of the Monchegorsk 2.5Ga, Kivakka 2.45Ga and Bushveld 2.06Ga layered intrusions was conducted for the first time. The low-Ti titanomagnetites Tc = 530-580o C are the main natural remanent magnetization NRM carriers. The high temperature NRM component according to petromagnetic characteristics is thermoremanent and was acquired at the cooling phase of the intrusion. The magnetic grains above 540o C are close to a single-domain state. The temperature versus time and cooling velocity versus temperature and time dependences during cooling of intrusions were calculated on the basis of solution of the Stefan problem and the nonstationary heat conduction problem. The geothermal gradient value was taken as 20okm-1. The unblocking temperatures in the course of thermal demagnetization of samples Td and the blocking temperatures during cooling from high temperatures Tb rate dependences were used for conversion of the Td to Tb Dodson and McClelland, 1980. A detailed thermal demagnetization at 2o-3o interval from 530oC up to 580oC was made and a pattern of behavior of the geomagnetic field direction was obtained afor the time of "running'' the Curie points over the section and bfor the cooling time of the intrusion at each sampling point from Tb = 580oC. A wavelet analysis has been used to study the field variation etc. The main rhythms of the direction variation spectrum are 3-4.5, 5-7, 8-10, 12, 15-17, 19-20, 30-40, 50-60, and 90-100kyr and they change in time. The length of rhythms is different and ranges from 1-2 oscillations "splashes'' up to 10-12. The Monchegorsk intrusion. The pole 265.3o E, 1.3o N. The length of record is ~70kyr. The geomagnetic excursion of the reversal polarity lasting for less than 2000 years and the R-subchron of ~60kyr were recorded. Kivakka intrusion. The A1 prefolded and A2 synfolded components which occurred at the stage of cooling of the intrusion are isolated. The body started to tilt approximately 85kyr after intrusion emplacement and it lasted for 20-25kyr. The pole of the A1 is 17.8oS and 247oE. Duration of the record is 35kyr and only one R-polarity existed during this period. Bushveld intrusion. Orientation of the horizontal plane of the samples has been restored from viscous magnetization and a paleomagnetic pole 12oN, 35.4oE has been determined from a high-temperature N-component of the NRM. A paleomagnetic record for ~500kyr was obtained; polarity of the field has changed only once during this period.

 geomagnetic field variations layered intrusions titanomagnetites petromagnetic characteristics Monchegorsk. geomagnetic field variations layered intrusions titanomagnetites petromagnetic characteristics Monchegorsk.

Amelin, Precambrian Res., v. 75, 1995., doi: 10.1016/0301-92689500015-W Amelin, Precambrian Res., v. 75, 1995., doi: 10.1016/0301-92689500015-W Amelin, Contrib. Mineral. Petrol., v. 124, 1996., doi: 10.1007/s004100050190 Amelin, Contrib. Mineral. Petrol., v. 124, 1996., doi: 10.1007/s004100050190 Balashov, Precambrian Res., v. 64, 1993., doi: 10.1016/0301-92689390076-E Balashov, Precambrian Res., v. 64, 1993., doi: 10.1016/0301-92689390076-E Berk, Recent history of the Earth, 1980. Berk, Recent history of the Earth, 1980. Buchanan, Earth Planet. Sci. Lett., v. 155, 1998., doi: 10.1016/S0012-821X9700216-1 Buchanan, Earth Planet. Sci. Lett., v. 155, 1998., doi: 10.1016/S0012-821X9700216-1 Buick, J. Geol. Soc. London, v. 158, no. 1, 2001. Buick, J. Geol. Soc. London, v. 158, no. 1, 2001. Buiko, Stratigraphy, Geologic correlation, v. 3, no. 4, 1995. Buiko, Stratigraphy, Geologic correlation, v. 3, no. 4, 1995. Cawthorn, J. Petrol., v. 39, no. 9, 1998., doi: 10.1093/petrology/39.9.1669 Cawthorn, J. Petrol., v. 39, no. 9, 1998., doi: 10.1093/petrology/39.9.1669 Chui, An Introduction to Wavelets, 1992. Chui, An Introduction to Wavelets, 1992. Coe, Earth Planet. Sci. Lett., v. 92, 1989., doi: 10.1016/0012-821X8990053-8 Coe, Earth Planet. Sci. Lett., v. 92, 1989., doi: 10.1016/0012-821X8990053-8 Coe, Nature, v. 374, 1995., doi: 10.1038/374687a0 Coe, Nature, v. 374, 1995., doi: 10.1038/374687a0 Crouzet, Geophys. J. Int., v. 145, 2001., doi: 10.1046/j.0956-540x.2001.01423.x Crouzet, Geophys. J. Int., v. 145, 2001., doi: 10.1046/j.0956-540x.2001.01423.x Crouzet, Geophys. J. Int., v. 146, 2001., doi: 10.1046/j.0956-540x.2001.01478.x Crouzet, Geophys. J. Int., v. 146, 2001., doi: 10.1046/j.0956-540x.2001.01478.x Crouzet, Geophys. J. R. Astron. Soc., v. 53, 1978. Crouzet, Geophys. J. R. Astron. Soc., v. 53, 1978. Daubechies, no. 61 in CBMS-NSF Series in Applied Mathematics, 1992. Daubechies, no. 61 in CBMS-NSF Series in Applied Mathematics, 1992. Day, Phys. Earth Planet. Inter., v. 13, 1977., doi: 10.1016/0031-92017790108-X Day, Phys. Earth Planet. Inter., v. 13, 1977., doi: 10.1016/0031-92017790108-X Dodson, Geophys. J. R. Astron. Soc., v. 53, 1978. Dodson, Geophys. J. R. Astron. Soc., v. 53, 1978. Dodson, J. Geophys. Res., v. 85, 1980. Dodson, J. Geophys. Res., v. 85, 1980. Dudarev, Heat Exchange in Magmatogene Processes, 1972. Dudarev, Heat Exchange in Magmatogene Processes, 1972. Dunlop, J. Geophys. Res., v. 107, no. B3, 2002., doi: 10.1029/2001JB000487 Dunlop, J. Geophys. Res., v. 107, no. B3, 2002., doi: 10.1029/2001JB000487 Eales, Layered intrusions, edited by R. G. Cawthorn, 1996. Eales, Layered intrusions, edited by R. G. Cawthorn, 1996. Ein, Materials of the conference "Riftogenesis magmatism and metallogeny of Pre-Cambrian, Correlation of geological complexes of Fennoscandia'', 2000. Ein, Materials of the conference "Riftogenesis magmatism and metallogeny of Pre-Cambrian, Correlation of geological complexes of Fennoscandia'', 2000. Elming, Tectonophysics, v. 223, 1993., doi: 10.1016/0040-19519390137-9 Elming, Tectonophysics, v. 223, 1993., doi: 10.1016/0040-19519390137-9 Engelbrecht, S. Afr. J. Geol., v. 93, no. 2, 1990. Engelbrecht, S. Afr. J. Geol., v. 93, no. 2, 1990. Enkin, A computer program package for analysis and presentation of palaeomagnetic data, 1994. Enkin, A computer program package for analysis and presentation of palaeomagnetic data, 1994. Hardle, Applied nonparametric regression, 1989. Hardle, Applied nonparametric regression, 1989. Hattingh, Earth Planet. Sci. Lett., v. 79, 1986., doi: 10.1016/0012-821X8690199-8 Hattingh, Earth Planet. Sci. Lett., v. 79, 1986., doi: 10.1016/0012-821X8690199-8 Hattingh, Tectonophysics, v. 124, 1986., doi: 10.1016/0040-19518690205-2 Hattingh, Tectonophysics, v. 124, 1986., doi: 10.1016/0040-19518690205-2 Hattingh, Tectonophysics, v. 165, 1989., doi: 10.1016/0040-19518990042-5 Hattingh, Tectonophysics, v. 165, 1989., doi: 10.1016/0040-19518990042-5 Hattingh, Precambrian Res., v. 69, 1994., doi: 10.1016/0301-92689490088-4 Hattingh, Precambrian Res., v. 69, 1994., doi: 10.1016/0301-92689490088-4 Khramov, Fizika Zemli, no. 6, 1997. Khramov, Fizika Zemli, no. 6, 1997. Khvorov, Geokhimiya, no. 8, 2003. Khvorov, Geokhimiya, no. 8, 2003. Khvorov, Obschie problemy petrologii, no. 1, 2000. Khvorov, Obschie problemy petrologii, no. 1, 2000. Kogarko, Alkaline rocks and carbonatites of the world, Pt 2: Former USSR, 1995. Kogarko, Alkaline rocks and carbonatites of the world, Pt 2: Former USSR, 1995. Koptev-Dvornikov, Petrologia, v. 9, 2001. Koptev-Dvornikov, Petrologia, v. 9, 2001. Kozlov, Natural Series of Nickel Bearing Intrusions and Their Metallogeny, 1973. Kozlov, Natural Series of Nickel Bearing Intrusions and Their Metallogeny, 1973. Krasnova, Precambrian Res., v. 74, 1995., doi: 10.1016/0301-92689500005-P Krasnova, Precambrian Res., v. 74, 1995., doi: 10.1016/0301-92689500005-P Lavrov, Pre-Cambrian ultrabasites and layered peridotite-gabbro-norite intrusions of the Northern Karelia, 1979. Lavrov, Pre-Cambrian ultrabasites and layered peridotite-gabbro-norite intrusions of the Northern Karelia, 1979. Levchenkov, Stratigrafia, Geologicheskaya korrelatsia, no. 1, 1994. Levchenkov, Stratigrafia, Geologicheskaya korrelatsia, no. 1, 1994. Mallat, A wavelet tour of signal processing, 1998. Mallat, A wavelet tour of signal processing, 1998. Mertanen, Geol. Surv. Finland, Espoo, 1995. Mertanen, Geol. Surv. Finland, Espoo, 1995. Mertanen, Geol. Surv. Finland, v. 347, 1989. Mertanen, Geol. Surv. Finland, v. 347, 1989. Mertanen, Precambrian Res., v. 98, 1999., doi: 10.1016/S0301-92689900050-9 Mertanen, Precambrian Res., v. 98, 1999., doi: 10.1016/S0301-92689900050-9 Nguen, Izv. AN SSSR, Fizika Zemli, no. 8, 1985. Nguen, Izv. AN SSSR, Fizika Zemli, no. 8, 1985. Nguen, Izv. AN SSSR, Fizika Zemli, no. 5, 1987. Nguen, Izv. AN SSSR, Fizika Zemli, no. 5, 1987. Pechersky, Fizika Zemli, no. 6, 2002. Pechersky, Fizika Zemli, no. 6, 2002. Pechersky, Fizika Zemli, no. 5, 2004. Pechersky, Fizika Zemli, no. 5, 2004. Pullaiah, Earth Planet. Sci. Lett., v. 28, 1975., doi: 10.1016/0012-821X7590221-6 Pullaiah, Earth Planet. Sci. Lett., v. 28, 1975., doi: 10.1016/0012-821X7590221-6 Rochette, Geophys. J. Int., v. 108, 1992., doi: 10.1111/j.1365-246X.1992.tb04630.x Rochette, Geophys. J. Int., v. 108, 1992., doi: 10.1111/j.1365-246X.1992.tb04630.x Saltikova, Deep fractures in the Paanajarvi--Kuusamo--Kuolajarvi area, Geological Survey of Finland, no. 13, edited by A. Silvennoinen, 1991. Saltikova, Deep fractures in the Paanajarvi--Kuusamo--Kuolajarvi area, Geological Survey of Finland, no. 13, edited by A. Silvennoinen, 1991. Scherbakov, Fizika Zemli, no. 5, 2002. Scherbakov, Fizika Zemli, no. 5, 2002. Schoenberg, Mineral. Mag, v. 62A, 1998. Schoenberg, Mineral. Mag, v. 62A, 1998. Sharkov, Petrology of the layered intrusions, 1980. Sharkov, Petrology of the layered intrusions, 1980. Sharkov, Petrologia, v. 5, 1997. Sharkov, Petrologia, v. 5, 1997. Sholpo, Use of the rock magnetism when solving geological problems, 1977. Sholpo, Use of the rock magnetism when solving geological problems, 1977. Silvennoinen, Deep fractures in the Paanaj#xE4;rvi--Kuusamo--Kuolaj#xE4;rvi area, Geol. Survey of Finland, no. 13, edited by A. Silvennoinen, 1991. Silvennoinen, Deep fractures in the Paanaj#xE4;rvi--Kuusamo--Kuolaj#xE4;rvi area, Geol. Survey of Finland, no. 13, edited by A. Silvennoinen, 1991. Thermal field..., Thermal field of the Europe, 1982. Thermal field..., Thermal field of the Europe, 1982. Tikhonov, Mathematical physics equations, 1966. Tikhonov, Mathematical physics equations, 1966. Turcotte, Geodynamics, 1985. Turcotte, Geodynamics, 1985. Valet, J. Geophys. Res., v. 103, 1998., doi: 10.1029/97JB03544 Valet, J. Geophys. Res., v. 103, 1998., doi: 10.1029/97JB03544 Wager, Igneous rocks, 1970. Wager, Igneous rocks, 1970. Williams, J. Geophys. Res., v. 87, 1982. Williams, J. Geophys. Res., v. 87, 1982.