Wyniki wyszukiwania - BazTech

1

Electromagnetic study of lithospheric structure in the marginal zone of East European Craton in NW Poland

Jóźwiak W.

Acta Geophysica

|

2013

|

Vol. 61, no. 5

1101-1129

EN

The marginal zone of the East European Platform, an area of key importance for our understanding of the geotectonic history of Europe, has been a challenge for geophysicists for many years. The basic research method is seismic survey, but many important data on physical properties and structure of the lithosphere may also be provided by the electromagnetic methods. In this paper, results of deep basement study by electromagnetic methods performed in Poland since the mid-1960s are presented. Over this time, several hundred long-period soundings have been executed providing an assessment of the electric conductivity distribution in the crust and upper mantle. Numerous 1D, 2D, and pseudo-3D electric conductivity models were constructed, and a new interpretation method based on Horizontal Magnetic Tensor analysis has been applied recently. The results show that the contact zone is of lithospheric discontinuity character and there are distinct differences in geoelectric structures between the Precambrian Platform, transitional zone (TESZ), and the Paleozoic Platform. The wide-spread conducting complexes in the crust with integral conductivity values reaching 10 000 S at 20–30 km depths are most spectacular. They are most likely consequences of geological processes related to Caledonian and Variscan orogenesis. The upper mantle conductivity is also variable, the thickness of high-resistive lithospheric plates ranging from 120–140 km under the Paleozoic Platform to 220–240 km under the East European Platform.

2

Badania struktury skorupy ziemskiej na obszarze Europy Centralnej, ze szczególnym uwzględnieniem Transeuropejskiej Strefy Szwu, metodami głębokich profilowań sejsmicznych

Guterch A.

Wiadomości Naftowe i Gazownicze

|

2012

|

R. 15, Nr 9 (173)

4--9

EN

The complex tectonic history of Central Europe (Fig. 1a) reflects the break-up of a Neoproterozoic supercontinet(s) (Rodinia/Pannotia) to form the fragment Baltica and the subsequent growth of continental Europe beginning with the Caledonian orogeny. Caledonian and younger Variscan orogenesis involved accretion of Laurentian and Gondwanan terranes to the riftet margin of Baltica. (East European craton, EEC) during the Paleozoic. From Central Poland northward, the region also experienced volcanic activity during the Permian and tectonic inversion during the Alpine orogeny, which in the south continues today. The Trans-European Suture Zone (TESZ) is a term used to refer to the suite of sutures and terranes that formed adjacent to the rifted margin of Baltica, and these features extend from the British Isles to the Black Sea region (Fig. 1a and 2). Understanding the structure and evolution of the TESZ region is one of the key tectonic challenges in Europe north of the Alps. The TESZ is far more complex than a single suture but in a broad sense is the boundary between the accreted terranes and Baltica. The TESZ includes the Teisseyre-Tornquist Zone (TTZ), which has several definitions. Here, we will use the term TTZ to refer to a structural zone associated with the southwestern edge of the EEC. Beginning in 1997, Central Europe, between the Baltic and Adriatic Seas, has been covered by an unprecedented network of seismic refraction experiments (Fig. 1b). These experiments - POLONAISE’97, CELEBRATION 2000, ALP 2002, and SUDETES 2003 - have only be possible due to a massive international cooperative effort. International Consortium consisted of 35 institutions from 16 countries in Europe and North America - Austria, Belarus, Canada, Croatia, Czech Republic, Denmark, Finland, Germany, Hungary, Lithuania, Poland, Russia, Slovakia, Slovenia, Turkey and the United States. The majority of the recording instruments was provided by the IRIS/ PASCAL Instrument Center and the University of Texas at El Paso (USA), the Geological Survey of Canada and other countries. For example, in the CELEBRATION experiment, the total number was 1230 stations ands 147 shot points located along seismic lines of a total length of about 9000 km. A large number of seismic sources and stations in all experiments means that besides 2 - D approach along profiles (Fig. 3 and 4), also 3 - D approach (Fig. 5 and 6) could be implemented in data interpretation. Total length of seismic profiles in all experiments is about 20 000 km (Fig. 1b).

3

Density and magnetic models of the lithosphere along CELEBRATION 2000 profile CEL01

Grabowska T., Bojdys G., Bielik M., Csicsay K.

Acta Geophysica

|

2011

|

Vol. 59, no. 3

526-560

EN

The paper presents 2D density and magnetic models of the crust and upper mantle along the DSS line profile of the CELEBRATION 2000 project that crosses the most important geological units in Central Europe. These are the Alps-Carpathians-Pannonian (ALCAPA) region, the SE part of the Paleozoic Platform (PLZ), the Trans-European Suture Zone (TESZ) and a fragment of the SW portion of the East European Craton (EEC). The density and magnetic models were constructed on the basis of a 2D model of P-wave velocity converted into density model, geological data as well as geothermal data and the results of integrated geophysical modelling for the lithosphere-asthenosphere boundary. This allowed us to construct a comprehensive geophysical 2D model of the crust and enlargement the geophysical-geological characteristics of the lithosphere in the Pannonian basins, the Carpathian orogen, and in the transitional zone between the ALCAPA plate and the East European Craton (passing through the Paleozoic Platform). As a result, we have provided evidence for the heterogeneity of the density in the lithospheric mantle, terrane concept of the East European Craton foreland, and confirmed the possibility of rift events along the SW boundary of the Precambrian craton in SE Poland.

4

Seismic structure of the lithosphere between the East European Craton and the Carpathians from the net of CELEBRATION 2000 profiles in SE Poland

Janik T., Grad M., Guterch A.

Geological Quarterly

|

2009

|

Vol. 53, No 1

141-158

EN

During the CELEBRATION 2000 experiment, the area of SE Poland was investigated by relatively dense system of deep seismic sounding profiles. Apart from five main profiles CEL01–CEL05, eight additional profiles were executed between the edge of the East European Craton and the Carphatians: CEL06, CEL11, CEL12, CEL13, CEL14, CEL21, CEL22 and CEL23. In this paper, we present results of modelling of refracted and reflected waves with use of a 2D ray tracing technique. All 13 profiles were jointly inter reted with verification of models at crossing points, and a quasi 3D model of the crust and upper mantle was developed. The obtained P-wave velocity models of the crust and uppermost mantle are very complex and show a differentiation of the seismic structure for tectonic units in SE Poland. The depth of the Moho discontinuity in the investigated area changes from about 30 to about 52 km. As a summary of all seismic models, the Moho depth map for SE Poland is presented, as well as a map of the extent of the most characteristic crustal elements in the area: a high velocity body in the upper crust, division into two- and three-layer consolidated crust, ranges of very deep layers with low velocities in the upper and middle crust, aproximate ranges of detected velocity anisotropy in the upper/middle crust, ranges of the high-velocity lower crust and high-velocity uppermost mantle. Both maps are com pared with the main struc tural el e ments from tec tonic map. This could form the base for a new geotectonic in ter pre ta tion of this com plex area.

5

Lithospheric structure across the Trans-European Suture Zone in NW Poland based on gravity data interpretation

Królikowski C., Petecki Z.

Geological Quarterly

|

2002

|

Vol. 46, No 3

235-246

EN

We provide an analysis of geophysical and geological data from the Baltic segment of the Trans-European Suture Zone (TESZ). The construction of structural and density maps of the Zechstein-Mesozoic-Cenozoic complex has allowed identification of anomalies of basement orgin. As a result of interpretation of these anomalies, major structural elements of the lithosphere have been characterised. According to gravity modelling the crustal structure is more complicated than shown on velocity model along refraction and wide-angle reflection profile LT-7. Long-wavelength anomalies have been modelled in terms of lateral heterogeneity within the lower crust and upper mantle. In order to achieve a match between the observed and calculated gravity effects, it was necessary to assume dense upper mantle beneath the TESZ. Gravity data also indicate the presence of high-density bodies in the upper crust, and a complex transitional zone between crust and upper mantle in the TESZ.