MANTLE ELECTROCONDUCTIVITY OF THE FENNOSCANDIAN SHIELD BY THE RESULTS OF COMBINED INTERPRETATION OF DEEP MTS AND GLOBAL MVS DATA

Abstract. The deep distribution of the mantle electroconductivity of the Fennoscandian Shield has been studied on the base of analysis of the international experiment BEAR data. For the analysis there where taken “longitudinal ” curves and maximal impedance phase curves which give good agreement with the global MVS curve. It was shown that till the depth 100 km “longitudinal ” and phase curves give different distributions but at the depths lower then 100 km these distributions practically coincide which makes it possible to build the common mean curve of the deep mantle conductivity distribution for all Fennoscandian Shield with exception of the regions with the anomalous mantle conductivity located in the northern part of the Bothnia Gulf and on the Belomorskiy block. The gradient of the electroconductivity has noticeable peculiarities only within the first 100-200 km of the mantle. Within the 200-600 km interval it does not noticeably change and increases again after 700 km depth. At the depth 1000 km the maximum of the conductivity can be seen. In order to rise the reliability of these results there is necessary to raise the quality of the MVS and MTS data within the interval of daily variations. For the analysis there were taken experiment BEAR data obtained in 45 sites of the Fennoscandian Shield within the period range from 10 s till 24 hours. Location of the sites is shown on the fig.1. On the figure there are shown also the main tectonic boundaries: between the Svecofennian geoblock at the South-West and the Karelian geoblock at the North-East, between the White Sea geoblock at the East and the Karelian geoblock and between the Caledonides at the West and the Svecofennian geoblock at the East