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Accurately modeling the anisotropic dielectric properties of shales is important for the interpretation of dielectric data acquired from shales as source rocks and unconventional reservoirs. We have developed a multiphase incremental model for the frequency dependent anisotropic dielectric properties of sedimentary rocks and presented an approach based on the developed model to simulate the measured anisotropic dielectric behaviors of artificial shales. The new model was built based on the theoretical basis of differential effective medium models for any number of mineral grain components aligned in any direction and was shown to be independent of the mixing order. The model incorporates the measured orientation distribution function of the clay particles to determine the shale dielectric anisotropy, and the frequency dependent dielectric behaviors of the wet clay minerals are obtained by inverting the dielectric properties of the artificial sample composed of clay and the same brine as in other artificial shales. The modeling technique combined important polarization mechanisms in the intermediate frequency range and was shown to give satisfactory fit to the measured frequency dependent anisotropic relative permittivity and conductivity of the artificial shales with varying silt contents by using a reasonable aspect ratio and constant dielectric parameters for the silt grains.

To understand the tectonic–magmatic history, crustal structure and crustal accretion mode of the Eurasian Basin in the Arctic, we calculated the crustal thickness, residual bathymetry (RB) and non-isostatic topography of the Eurasian Basin by using the latest bathymetry, free-air gravity anomaly, crustal age and sediment thickness data. The tectonic–magmatic process of the Eurasian Basin can be divided into two stages. During magnetic isochrons 24-13 (C24-C13), the crustal structure of the basin was characterized by regional variations, while the crustal structure of the basin was characterized by local variations during magnetic isochrons 13-0 (C13-0). On the whole, the western part of the basin had a thicker crustal thickness and higher RB than the eastern part of the basin during C24-C13, which should result from the northward movement of Greenland. During magnetic isochrons 24-20 (C24-C20), the crustal structure of the eastern part of the basin had abnormally strong asymmetry. We speculate that there may be mantle upwelling beneath the Kara Sea Shelf in the south of the Eastern Eurasian Basin, which provides a large amount of melt for the crustal accretion of the southern part of the Eastern Eurasian Basin. The melt focusing supply could generate abnormally thick crust (>7 km) during magma enhancement period. The Western Eurasian Basin had stronger spatial variability and more frequency asymmetric polarity reversal than the Eastern Eurasian Basin during magnetic isochrons 6-0 (C6-0). We attribute this to the inflow of the North Atlantic mantle.

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