Mantle gravitational anomalies in the regions of Eurasia, North America and the Atlantic

Abstract

The construction of density models of the Earth's crust and upper mantle along the system of profiles crossing Eurasia and North America, the Atlantic Ocean, and transition zones between continents and oceans, begun by the works of the authors of recent years, is continued. In the crust, they are plotted by velocity sections along DSS profiles. The calculated effect of the section in anomalous densities in relation to the normal platform mantle (minus 870 mGl) corresponds to the zero observed field (Bouguer anomalies on land and Fay anomalies on sea). This value is established experimentally on the East European platform, where the geological and geophysical knowledge is the maximum. In the upper mantle, the authors' ideas about deep processes are used. They are associated with variants of heat and mass transfer under various endogenous regimes. Based on the results of these processes, temperature distribution that distinguish the densities of mantle rocks in each region from platform ones was determined. The gravitational effects calculated for such anomalous models are summarized with the crustal ones. Regions with all types of endogenous regimes were studied: platforms, zones of recent activation, geosynclines and rifts of different ages, mid-ocean ridge, oceanic depressions, marginal trench, island arc, back-arc depression. The total has compared with the observed fields. In all previously studied regions, the obtained differences do not exceed those explained by the errors of observations and calculations. Thus, the construction of density models of the tectonosphere becomes one of the methods for verifying the used schemes of deep processes. In the regions covered by recent activation and in the transition zones between continents and oceans, the differences between the experimental and calculated data turned out to be the maximum. Therefore, the work was continued using other DSS profiles, mainly on the continental platforms. The result generally confirmed the previous one, revealing additional modeling problems associated with velocity cross sections of the earth's crust.