TY - JOUR

T1 - Typical characteristics of the earth’s magnetic and gravity fields related to global and regional tectonics

AU - Dobretsov, N. L.

AU - Metelkin, D. V.

AU - Vasilevskiy, A. N.

N1 - Funding Information: We are sincerely grateful to corresponding members of the RAS A.N. Didenko and I.Yu. Koulakov for constructive criticism of the manuscript. This work was financially supported by the Russian Science Foundation (project no. 19-17-00091), the Russian Foundation for Basic Research (projects nos. 18-05-70035 and 18-05-00234) and the Ministry of Science and Higher Education of the RF (project no. FSUS-2020-0039). Publisher Copyright: © 2021, V.S. Sobolev IGM, Siberian Branch of the RAS.

PY - 2021

Y1 - 2021

N2 - We present a summary and analysis of current views on the magnetic and gravity fields of the Earth as a reflection of global and regional tectonic processes. The discussion concerns the probable interconnection between the distribution of the geomagnetic field characteristics, gravity anomalies and the manifestations of mantle plume magmatism as the most remarkable geologic indicator of deep geodynamics. We demonstrate that the distribution of the characteristics of the main geomagnetic field has a qualitative similarity to anomalies of the gravity field. Brief variations of the geomagnetic field are due to high-frequency oscillations in the ionosphere, do not affect the general state of the field, and are useless when considering issues of global tectonics. On the contrary, variations with long periodicities, first of all geomagnetic reversals, can be among the main indicators of the evolution of the geodynamo – the heat mechanism controlling the entire series of global tectonic processes. The frequency of reversals is determined by the intensity of mantle plumes that cause the cooling of the core, increase the convection rate in the asthenosphere, and respectively, the periodic changes in the tectonosphere. We assume the existence of three modes of behavior for this system. The first one corresponds to steady convection, in which reversals are extremely rare or do not happen at all. These episodes – superchrons – compose no more than 20% of the duration of the Phanerozoic. The second mode occurs significantly more often in the geologic history and is characterized by active convection with frequent reversals happening at least once every 5 Myr. Finally, the third mode, which is rare for the Phanerozoic but was probably more prevalent in the early Precambrian, corresponds to hyperactive turbulent convection, when the frequency of reversals reached 20 and possibly more during one million years. Although the demonstrated qualitative similarity in the position of extreme values of the main geomagnetic field, the centers of free air gravity anomalies, and manifestations of large igneous provinces does not yet have a credible explanation, we consider it to be fundamental and requiring special study and detailed elaboration.

AB - We present a summary and analysis of current views on the magnetic and gravity fields of the Earth as a reflection of global and regional tectonic processes. The discussion concerns the probable interconnection between the distribution of the geomagnetic field characteristics, gravity anomalies and the manifestations of mantle plume magmatism as the most remarkable geologic indicator of deep geodynamics. We demonstrate that the distribution of the characteristics of the main geomagnetic field has a qualitative similarity to anomalies of the gravity field. Brief variations of the geomagnetic field are due to high-frequency oscillations in the ionosphere, do not affect the general state of the field, and are useless when considering issues of global tectonics. On the contrary, variations with long periodicities, first of all geomagnetic reversals, can be among the main indicators of the evolution of the geodynamo – the heat mechanism controlling the entire series of global tectonic processes. The frequency of reversals is determined by the intensity of mantle plumes that cause the cooling of the core, increase the convection rate in the asthenosphere, and respectively, the periodic changes in the tectonosphere. We assume the existence of three modes of behavior for this system. The first one corresponds to steady convection, in which reversals are extremely rare or do not happen at all. These episodes – superchrons – compose no more than 20% of the duration of the Phanerozoic. The second mode occurs significantly more often in the geologic history and is characterized by active convection with frequent reversals happening at least once every 5 Myr. Finally, the third mode, which is rare for the Phanerozoic but was probably more prevalent in the early Precambrian, corresponds to hyperactive turbulent convection, when the frequency of reversals reached 20 and possibly more during one million years. Although the demonstrated qualitative similarity in the position of extreme values of the main geomagnetic field, the centers of free air gravity anomalies, and manifestations of large igneous provinces does not yet have a credible explanation, we consider it to be fundamental and requiring special study and detailed elaboration.

KW - Geodynamo

KW - Geomagnetic field

KW - Geomagnetic reversals

KW - Global tectonic

KW - Gravity anomalies

KW - Mantle plumes

UR - http://www.scopus.com/inward/record.url?scp=85106254943&partnerID=8YFLogxK

UR - https://www.elibrary.ru/item.asp?id=46071509

U2 - 10.2113/RGG20204261

DO - 10.2113/RGG20204261

M3 - Article

AN - SCOPUS:85106254943

VL - 62

SP - 6

EP - 24

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

IS - 1

M1 - 2

ER -