Posgay K.,Magyar Allami Eotvos Lorand Geofi Zikai Intezet |
Bodoky T.,Magyar Allami Eotvos Lorand Geofi Zikai Intezet |
Falus G.,Magyar Allami Eotvos Lorand Geofi Zikai Intezet |
Kovacs I.J.,Magyar Allami Eotvos Lorand Geofi Zikai Intezet |
And 4 more authors.
Magyar Geofizika | Year: 2011
Comparing the deep refl ection seismic profi les (PGT-1, ÉK-2) measured along the Hungarian Geotraverse with geological, magnetotelluric and geochemical data we came to the conclusion that on the surface of the Pre-Cenozoic basement there is a sequence of rocks which is repeated several times along the Geotraverse. That sequence is composed of metamorphic rocks and of Triassic, Jurassic and Cretaceous beds superimposed on them with SSE line of dip and forming belts with SWW-NEE strike. Rows of characteristic refl ections can be observed which are started at the edges of the belts and run along zones of the section sloping towards the SSE part of the profi le. From those dislocation zones can be deduced, which divide the investigated part of Tisza unit into thick plate like blocks. This lithosphere structure might be formed when a branch of the Vardar Ocean (which joined to the Száva-Bükk unit) was pushed under the Tisza unit about during the Lower Cretaceous. The Pre-Cenozoic basement is intersected by the subduction surface along the Mid-Hungarian Line (at least nearby the Hungarian Geotravers). This idea is backed up by the followings: - Those refl ections which are parallel to the dislocation belt starting in the vicinity of the Mid-Hungarian Line and slope towards SSE indicate displacement surfaces. - On the Northern part of the Geotravers (ÉK-2 section) the continuations of these refl ections bend into horizontal direction. From that we may conclude a NNW directional decrease of the sloping of the plate, namely the nearly horizontal part of the plate subducting in SSE direction. - On that upper part of the subducting plate a low resistivity zone revealed by magnetotellurics can be followed to large depth. Presumably this zone sloping SSE indicates a higher water content of the plate which might be bound in chain silicates (amphiboles and micas). The results of our investigation show that on the studied part of the Tisza unit the structure of the thick plate under the flysch is similar to those of its other parts along the Hungarian Geotraverse, namely under the flysch from NNW to SSE crystalline rocks and Triassic, Jurassic and Cretaceous beds superimposed on them can be found. It is conceivable that those layers got into a depth of CH generation protected by flysch. © 2011 Magyar Geofi zikusok Egyesülete.
Kiss J.,Magyar Allami Eotvos Lorand Geofi Zikai Intezet |
Zilahi-Sebess L.,Magyar Allami Eotvos Lorand Geofi Zikai Intezet |
Szarka L.,MTA Geodeziai Es Geofi Zikai Kutatointezet
Magyar Geofizika | Year: 2011
The ability of rocks to be magnetized is caused primarily by the magnetic minerals found within them. In the case of transitional metals, such as Fe, Co, and Ni (potential ferromagnets), the magnetic momentums related to the spin of the empty 3d or 4f electron shell have a value other than zero. The reason for the observable spontaneous magnetic orderliness in these ferromagnets is the mutual effect of exchange between the uncompensated magnetic momentums, related to the electron spin of the neighbouring atoms, the magnitude of which can be characterized by the size of the overlapping of the wave functions of the appropriate orbits. Thus, ferromagnetism arises only alongside certain parameters of the crystal structure: when the atom diameter is at least 1.5 times that of the empty 3d or 4f electron shells. This ratio of diameters depends on the constants of the lattice that is on the chemical environment of the magnetizable transitional metal atom. Because the lattice constants depend upon temperature, pressure, and lattice symmetry, so does the ability to be magnetized. In the case of sulphides for example, the maximum magnetization is not with the FeS composition, rather with the Fe1-xS composition. In other words, it is apparently the excess sulphur which increases magnetizability, but it is the bond lengths which have a decisive role. For the same reason, the magnetizability of iron oxides decreases with the increase in the degree of oxidization. © 2011 Magyar Geofi zikusok Egyesülete.