Large-Scale Crustal Conductivity Pattern in Central Europe and Its Correlation to Deep Tectonic Structures

Abstract

Abstract-The results of magnetovariational (MV) soundings are usually presented in the form of induction arrows. However, many examples show that the horizontal magnetic tensor (HMT) is more informative. The distribution of some HMT invariants directly traces the location of well-conducting rocks in the crust and upper mantle. The HMT determination requires simultaneous observations in an entire region, which is a substantial disadvantage. Yet, it is possible to apply techniques capable of restoring all the magnetic field components necessary for HMT estimation from tipper data arrays alone. These techniques exploit the spatial relationships between electromagnetic field components in a nonconducting atmosphere. For Central Europe, a large data set of induction arrows has been collected by the effort of many groups during the last 50 years. Based on these data, HMT values were calculated, and the results are very significant. The spatial behavior of certain HMT invariants demonstrates the presence of deeply seated, well-conducting rocks in the crust. Anomaly maximums display an arc-shaped trend that may be genetically linked with the Caledonian and/or Variscan margin thrust belts, which developed following the collision between Baltica and Avalonia and/or Gondwana-derived terranes, respectively. This is an important finding because the position of these deformation fronts in relation to the edge of the East European Platform is still controversial.

Basement structure of the Paleozoic Platform in Poland

“…The data have been re processed in or der to better visu al ise ma jor re gional fea tures of the base ment struc ture. Lastly, re sults of magnetotelluric in ves ti gations have been also taken into ac count (Ernst et al, 2002;Jozwiak, 2012).…”

“…3a). The lat ter struc ture has been at trib uted by Jozwiak (2012) to the Variscan De for ma tion Front. The sub-Zechstein tec tonic discon ti nu ities in ter preted by Krzywiec (2006) and Krzywiec et al (2006) in NW Po land partly con form with the course of the Pomer a nian Su ture in ter preted in this study.…”

Conductivity Anomalies in Central Europe

“…Since P14 is based on inversion of all local transfer functions (TE mode, TM mode, and induction arrows) and MVB only on the latter, the first model should be regarded as more reliable in terms of this feature. (b) The anomalous horizontal magnetic field shown in Jozwiak (2012), that reflects the results of Wybraniec et al (1999), but with better resolution, suggests that the continuous mid-crustal conductor in the centre of the LT7 model (Fig. 2) should consist of two laterally distinguishable parts.…”

“…According to Hoffmann et al (2008) and Jozwiak (2012), the results of these magnetotelluric and geomagnetic studies suggest a correction of the hitherto assumed position of both the Caledonian Deformation Front and the Trans-European Fault (the proper suture between Baltica and Avalonia) more to the south. The nature of these conductors is assumed by all authors, i.e.…”

“…The images presented in their paper are definitely impressive and highly informative, and it represents the latest endeavour to give a qualitative overview of European conductivity structures, even if no attempt was made to interpret them. The approach of working with the anomalous horizontal magnetic field has been readopted and refined in a number of recent works (Habibian et al 2010;Nowo_ zyński 2012;Jozwiak 2012).…”