Long-wavelength magnetic anomalies as a source of information about deep crustal structure
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Vols. 1-18 (1924-1944), ISSN 0044-2801
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Abstract
The nature of long-wavelength magnetic anomalies (λ = 60–300 km) computed for the Ukrainian Shield from the original field by a continuation upward to a height of 10 km is studied. The correlation betweeen the regional anomalies, the crustal thickness and the topography of the Curie isotherm of magnetite is examined. The strongest correlation is established between the regional anomalies and the crustal thickness. Similar results have been obtained by us for the Baltic Shield and by D.H. Hall for the Canadian Shield. It is concluded that the entire lower crust is magnetized, the average magnetization being almost the same for all the ancient shields. These results have been used for the construction of a magnetic model of the Earth's crust. With some exceptions, the magnetization of the lower crust is found to be inhomogeneous and 5-10 times higher than that of the upper crust. Theoretical modelling and experimental results show a high magnetization in the entire sequence of blocks for the case of a thickened crust and, vice versa, weakly magnetized rocks correspond to a smaller thickness of the crust. The present approach may be of potential use for distinguishing and studying crust-upper mantle interaction areas as well as for predicting the topography of the Moho discontinuity.
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References
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