An integrated paleomagnetic and magnetic anisotropy study of the Oligocene flysch from the Dukla nappe, Outer Western Carpathians, Poland

The Dukla Nappe belongs to the Outer Western Carpathians, which suffered considerable shortening due to the convergence and collision of the European and African plates. In this paper we present new paleomagnetic and magnetic anisotropy results from the Polish part of the Dukla Nappe, based on 102 individually oriented cores from nine geographically distributed localities. Susceptibility measurements and mineralogy investigations showed that paramagnetic minerals are important contributors to susceptibility anisotropy (AMS). The AMS fabrics are related to deposition/compression (foliation) and weak tectonic deformation (lineation). The AARM fabric, that of the ferrimagnetic minerals, seems to be a less sensitive indicator of tectonic deformation than the AMS fabric. The inclination-only test points to the pre-folding age of the remanent magnetizations. Seven localities exhibit CCW rotation, a single one shows CW rotation. The CCW rotated paleomagnetic directions form two groups, one showing large, the other moderate CCW rotation. Previously published paleomagentic directions from the Slovak part of the same nappe exhibit smeared distribution between them. The declination of the overall-mean paleomagnetic direction for the Dukla nappe is similar to those observed in the neighbouring Magura and Silesian nappes, but it is of poorer quality. The AMS lineations at several localities are deviating more to the west from the present north than that of the local tectonic strikes. A possible explanation for this is that the AMS lineations were imprinted first, probably still in the Oligocene, while the sediments were soft (ductile deformation) and the folding and tilting took place during the CCW rotation. © 2016 Geologica Carpathica

Reconstruction of early phase deformations by integrated magnetic and mesotectonic data evaluation

Markers of brittle faulting are widely used for recovering past deformation phases. Rocks often have oriented magnetic fabrics, which can be interpreted as connected to ductile deformation before cementation of the sediment. This paper reports a novel statistical procedure for simultaneous evaluation of AMS (Anisotropy of Magnetic Susceptibility) and fault-slip data. The new method analyzes the AMS data, without linearization techniques, so that weak AMS lineation and rotational AMS can be assessed that are beyond the scope of classical methods. This idea is extended to the evaluation of fault-slip data. While the traditional assumptions of stress inversion are not rejected, the method recovers the stress field via statistical hypothesis testing. In addition it provides statistical information needed for the combined evaluation of the AMS and the mesotectonic (0.1 to 10 m) data. In the combined evaluation a statistical test is carried out that helps to decide if the AMS lineation and the mesotectonic markers (in case of repeated deformation of the oldest set of markers) were formed in the same or different deformation phases. If this condition is met, the combined evaluation can improve the precision of the reconstruction. When the two data sets do not have a common solution for the direction of the extension, the deformational origin of the AMS is questionable. In this case the orientation of the stress field responsible for the AMS lineation might be different from that which caused the brittle deformation. Although most of the examples demonstrate the reconstruction of weak deformations in sediments, the new method is readily applicable to investigate the ductile-brittle transition of any rock formation as long as AMS and fault-slip data are available

Tracking magnetic pollutants by integrated mineralogical and magnetic analyses of airborne particles in urban environment

This complex magnetic and mineralogical study, which was carried out on settled dust and PM10 (particulate matter smaller than 10 μm) samples collected for several years in a Hungarian industrial town, Miskolc. The primary aim of the research was to estimate the contribution of different pollution sources which produce magnetic phases to the settled dust and to the PM10 fraction. In both types of the airborne dust, magnetite a spinel type iron oxide was identified as the dominant magnetic mineral with magnetic and mineralogical methods. The latter revealed that the magnetic mineral was either pure magnetite or contained minor amounts, usually few percent in total of other metals like Mn (up to 2.2 at%), Zn (up to 4.6 at%), Co (up to 8.1 at%), Cr (up to 1.3 at%) and Pb (up to 0.5 at%). Comparison between the total magnetic susceptibilities of settled dust samples collected before and after the closing down, respectively of the steel works (DAM) in the town, reveals a significant reduction (50–100%) in magnetic pollution. Such comparison was not possible for PM10 fraction, since systematic PM10 collection in Miskolc started after the closing of DAM. The analysis of the PM10 filters was, however, important from the viewpoint of magnetic pollution originating from other sources, like vehicle traffic, combustion. We found that roughly the half of the magnetic particles are in the superparamagnetic range (< 30 nm), therefore extremely dangerous for the health. The degree of magnetic pollution shows daily and seasonal variations. The former points to vehicle traffic as a general source of magnetic grains, since the total susceptibility is lowest on Sundays (15*10-6 SI, till on weekdays ca. 20*10-6 SI). The seasonal variation indicates that industrial and household combustion increases the total susceptibility in winter time (from 5 to 8*10-6 SI in PM10). The mass of the PM10, however, increases much more (ca. 3 times) in wintertime than total susceptibility due to emission of large amount of non-magnetic particles, such as carbonaceous phases and sulphates from combustion sources. Thus, we think that restriction of vehicle traffic during wintertime is not an efficient measure to reduce the concentration of PM10 during smog alarm. Comparison between the concentrations of heavy metals (like Pb and Cd) and mass susceptibility lead to the conclusion that the magnetic pollutants and the metals are coming from different sources. The concentration of the latter depends on the direction and intensity of the wind, which may bring them form industrial sources, located North of Miskolc