Jana Dérerová

Calculation of temperature distribution and rheological properties of the lithosphere along geotransect in the Red Sea region

Abstract The temperature model of the lithosphere along profile passing through the Red Sea region has been derived using 2D integrated geophysical modelling method. Using the extrapolation of failure criteria, lithology and calculated temperature distribution, we have constructed the rheological model of the lithosphere in the area. We have calculated the strength distribution in the lithosphere and constructed the strength envelopes for both compressional and extensional regimes. The obtained results indicate that the strength steadily decreases from the Western desert through the Eastern desert towards the Red Sea where it reaches its minimum for both compressional and extensional regime. Maximum strength can be observed in the Western desert where the largest strength reaches values of about 250–300 MPa within the upper crust on the boundary between upper and lower crust. In the Eastern desert we observe slightly decreased strength with max values about 200–250 MPa within upper crust within 15 km with compression being dominant. These results suggest mostly rigid deformation in the region or Western and Eastern desert. In the Red Sea, the strength rapidly decreases to its minimum suggesting ductile processes as a result of higher temperatures.

Calculation of temperature distribution and rheological properties of the lithosphere along Profile 1 passing through Aswan

Abstract The 2D integrated geophysical modelling approach has been used to determine the temperature distribution in the lithosphere along the profile passing through Aswan. Based on the temperature model and the rheological parameters, we have calculated strength distribution in the lithosphere for the studied profile. The strength envelopes have been calculated for both compressional and extensional regimes. Our results indicate that the strength is constant along the whole length of the profile passing through the Nubia plain. The largest strength can be observed within the upper crust which allows us to assume rigid deformation in this part of the lithosphere, with compressional processes predominant. Towards the lower crust and upper mantle, strength values rapidly decrease for both regimes, suggesting ductile deformations in the lower part of the lithosphere.

A new lithospheric model in the eastern part of the Western Carpatians: 2D integrated modelling

Abstract Using 2D integrated geophysical modelling we recalculated lithospheric model along transect KP-X in the eastern part of the Western Carpathians. Our model takes into account the joint interpretation of the heat flow, free air anomalies, topography and geoid data. A more accurate model of lithospheric structure has been created, especially the lithosphere-astenosphere boundary. Lithosphere thickness in the study region increases from the area of the Pannonian Basin where we modelled it at the depth of 80 km towards the oldest and coolest area of the European Platform where it reaches about 150 km. In the Pannonian Basin the modelled Moho depths reach about of 25 km and it decreases towards theWestern Carpathians. The Western Carpathian’s crustal thickness varies from about 30 km to 45 km. The largest crustal thickness (45 km) has been located beneath the Externides (Carpathian Foredeep) of the Western Carpathians. In the direction of the European platform a Moho depth gradually increases until the end of the profile, where the crustal thickness reaches of about 42 km. Our modelling has confirmed the existence of an anomalous body with average density of 2850 kgm−3 seated mostly in the lower crust. Its uppermost boundary reaches a depth of about 12 km. The lower crust beneath the Western Carpathian Externides is much thicker (20 km) in comparison beneath the Pannonian Basin, where it is only 8 km on average.

2D density model of the Chinese continental lithosphere along a NW-SE transect

Abstract This paper presents a 2D density model along a transect from NW to SE China. The model was first constructed by the transformation of seismic velocity to density, revealed by previous deep seismic soundings (DSS) investigations in China. Then, the 2D density model was updated using the GM-SYS software by fitting the computed to the observed gravity data. Based on the density distribution of anomalous layers we divided the Chinese continental crust along the transect into three regions: north-western, central and south-eastern. The first one includes the Junggar Basin, Tianshan and Tarim Basin. The second part consists of the Qilian Orogen, the Qaidam Basin and the Songpan Ganzi Basin. The third region is represented by the Yangtze and the Cathaysia blocks. The low velocity body (vp =5.2 – 6.2 km/s) at the junction of the North-western and Central parts at a depth between 21 – 31 km, which was discovered out by DSS, was also confirmed by our 2D density modelling.

Calculation of temperature distribution and rheological properties of the lithosphere along transect II in the Western Carpathian-Pannonian Basin region

Abstract The temperature model of the lithosphere along transect II passing through the Western Carpathians and the Pannonian Basin has been calculated using 2D integrated geophysical modelling methodology. Based on the extrapolation of failure criteria, lithology and calculated temperature distribution, we derived the rheology model of the lithosphere in the area. Our results indicate a decrease of the lithospheric strength from the European platform and the Western Carpathians towards the Pannonian Basin. The largest strength can be observed within the upper crust which suggests rigid deformation in this part of the lithosphere. In the lithospheric mantle, strength almost disappears which allows us to assume that the ductile deformation dominates in this part of the lithosphere

Geophysical survey of Neovolcanic complexes in the first protection zone of the Sliač Spa and the Baková jama

Abstract The main purpose of the survey in the 1st protection zone area of the Sliač Spa and the Baková jama was to clarify the geological-tectonical structure. The vertical electric sounding (VES) technique was selected as the main geophysical survey method. Additionally, the soil radon emanometry was carried out to verify tectonic lines’ presence. The outcrop of Pre-Tertiary basement was discovered in the form of small isolated island. No tectonic line was identified based on the evaluation of profile radon concentration. The results of geoelectrical measurements are presented in 8 geological-geophysical crosssections. The results and the tectonic lines’ courses interpreted by the VES method are drawn in the map of new indications. The isoline maps and 3D model of Pre-Tertiary basement were constructed.

Calculation of temperature distribution and rheological properties of the lithosphere along transect I in the Western Carpathians

Abstract Using the 2D integrated modelling method, we calculated the temperature model of the lithosphere along transect I passing through theWestern Carpathians. Based on the extrapolation of failure criteria, lithology and calculated temperature distribution, we derived the rheology model of the lithosphere in the area. Our results indicate clearly that the strength decreases from the Bohemian Massif via the Western Carpathians to the Pannonian Basin. The largest strength can be observed within the upper crust on the boundary between the upper and lower crust. This phenomenon is typical for all studied tectonic units: the Bohemian Massif, the Western Carpathians and the Pannonian Basin. These results suggest mostly rigid deformation in the upper crust of the units. By contrast, the lower crust in the Bohemian Massif and the Western Carpathians reflects significantly lower strength, while in the Pannonian Basin the strength is the smallest. In all tectonic units the strength within the uppermost mantle (lower lithosphere) disappears. It can be suggested that the ductile deformation dominates in this part of the lithosphere.

Robustness analysis in forward modelling gravity data in crustal/lithospheric studies

Robustness analysis in forward modelling gravity data in crustal/lithospheric studies The robustness of the gravimetric forward modelling is investigated by applying the harmonic inversion procedure at the input which is the difference of the calculated and measured surface gravity. The gravity data are taken from two profiles in the Carpathian-Pannonian Basin region. The result of the inversion are density models obtained from the original two-layer models with various horizontal boundary depth and density contrast. The deformation of the originally planar boundary is the measure of the mismatch between calculated and measured data. The calculated deformation has reached up to tens of kilometers and thus the uncertainties in determining the geometry of disturbing bodies by the forward modelling are substantial.