Geophysical research: article

Hydration of the lithosphere and oceanic magnetic field
A. Gorodnitskiy
Y. Brusilovskiy
A. Ivanenko
K. Popov
N. Shishkina
I. Veklich
Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
Journal: Geophysical research
Tome: 18
Number: 4
Year: 2017
Pages: 32-49
UDK: 550.838.3
DOI: 10.21455/gr2017.4-3
Full text
Keywords: serpentinization, natural residual magnetization, magnetic anomalies, hydration, intraplate aseismic uplifts, magnetic layer model, effective magnetization, inverse problem, sources of anomalies
Аnnotation: A joint analysis of the results of geomagnetic surveys and the data of petromagnetic study of samples from different geotectonic zones of the World Ocean indicates that, along with the basaltic layer, deep sources, which are associated with serpentinite formations, make an important contribution to the anomalous magnetic field of the ocean. These formations are formed as a result of hydration by the oceanic water of hyperbasites of the upper mantle. The depth of penetration of oceanic water into the mantle is determined by the depth of the surface of the elastic-plastic transition, where the microcracks in the substance are melted, and its deformation begins to occur due to plastic flow. Numerous petromagnetic studies of oceanic serpentinites show that the main carrier of magnetism in them is magnetite, amounting to 5% or more. The magnetic parameters of magnetite in serpentinites are determined not only by its quantity, but also by the shape of its grains and by the nature of their distribution. According to different conditions of formation of serpentinite massifs in the main morphostructures of the ocean floor, four main morphogenetic types of such formations are distinguished: serpentinites of rift zones of mid-oceanic ridges, serpentinites of zones of transform faults, serpentinites of zones of intra-plate aseismic uplifts, and serpentinites of subduction zones. Based on the solution of the inverse magnetic problem, computer models of the sources of magnetic anomalies are constructed for the typical structures from all these zones. A complex petrophysical analysis of the available samples was also carried out. On the basis of a joint interpretation of these data with the results of other geophysical methods, convincing evidence for the existence of serpentinite formations in various geotectonic zones of the World Ocean has been obtained.