Maria Jeleńska

Dependence of anisotropy of magnetic susceptibility of rocks on temperature

Abstract The influence of heating on the low-field magnetic susceptibility K and its anisotropy, AMS, has been studied in some sedimentary, igneous and metamorphic rocks. The results show that heating causes a better grouping of the anisotropy ellipsoid axes, especially in sediments. In all the rocks studied, the AMS is mainly due to the matrix, i.e. paramagnetic and diamagnetic minerals, rather than the ferromagnetic minerals. The AMS of the diamagnetic components is removed during heating. An experiment involving thermal remagnetization of one sediment sample indicates that the processes of thermal magnetization do not influence the directions of anisotropy axes in this rock.

Paleomagnetic investigations of mesozoic and paleozoic rocks from Svalbard

Abstract A paleomagnetic study of Late Mesozoic dolente dykes and sills and Paleozoic sediments from Spitsbergen, the main island of the Svalbard Archipelago, gives the position of the pole in the Late Mesozoic and Paleozoic as distinct from the corresponding poles of Europe and North America. The Paleozoic pole is to the south of corresponding poles for Europe and North America. The data suggest that Svalbard has moved independently of Europe and North America at least in the Late Mesozoic, and thus might behave as a microplate or block.

Dependence of air pollution on meteorological conditions based on magnetic susceptibility measurements: a case study from Warsaw

This study reports systematic analysis of air pollution concentration by particulate matter (PM) in relation to annual changes of metrological conditions. The concentration of PM collected on filters was evaluated by magnetic properties. Long series of filters collected during 1977, 1980, 1981 and 1985 in Warsaw have been used for measurement. Such long time series allowed a better determination of correlation between seasonal susceptibility changes and meteorological conditions and to verify the repeatability of annual behavior. The magnetic susceptibility normalized by mass (χ) has been used as a proxy of pollution. Monthly variations of χ (χm) demonstrated slow and small seasonal changes disturbed by quick, high peaks. The filters with high susceptibilities contain a mixture of magnetic single and multidomain grains which is characteristic for anthropogenic pollution, with the frequency-dependent susceptibility χfd being less than 4%. The low susceptibility samples are characterized by admixture of small amount of pseudo-single domain (PSD) and possible small amount of superparamagnetic (SP) grains. Detailed analysis of reduced mean monthly susceptibility χR revealed that temperature and absolute humidity correlate positively in cold period of year and negatively in warm months. The linear correlation coefficients range from 0.7 to 0.9 and from 0.3 to 0.4 for negative and positive linear correlation, respectively. The dispersion of pollutants in a city depends on the way of ventilation. The big cities like Warsaw are urban heat islands which act the most effective way for the warm period and for the cold time. The correlation of χR with absolute humidity is similar to that for temperature but for different reasons. The presence of big amount of water vapor particles in the atmosphere can favor the adhesion of smaller ferromagnetic grains to their surface which can accelerate the process of falling down of such agglomerates. Such a process can take place during wintertime. We do not observe clear correlation between χR and precipitation.

Palaeomagnetism of the Upper Carboniferous Strzegom and Karkonosze Granites and the Kudowa Granitoid from the Sudet Mountains, Poland

Abstract Carboniferous granites and granitoids, varying in age from 305 to 281 Ma, from the Sudet mountains (latitude 51N, longitude 16E), Poland, carry dual-polarity magnetic components consisting of an inferred primary high-temperature A-component found in the Strzegom Granite, the Karkonosze Granite with the bordering Karpacz Hornfels and the Kudowa Granitoid and scattered low-stability components of Mesozoic-Tertiary age present in all rocks except the Strzegom Granite. The group-A component defines a palaeomagnetic pole position ( D = 202, I = − 12, α 95 = 13.0, N = 4, calculated palaeomagnetic pole position 42°S, 346°E) which is in good agreement with palaeomagnetic results from rocks of similar age in western Europe, thus implying that no major tectonic movement has taken place in the Sudets relative to stable Europe since Upper Carboniferous times.

Aspects of pre-Tertiary paleomagnetism of Spitsbergen and their tectonic implications

Abstract Paleomagnetic investigations were carried out on Cretaceous dolente dykes and sills, Permian limestones, Permo-Carboniferous limestones and Lower Devonian sandstones from different parts of Spitsbergen. Detailed rock magnetic studies showed that the main magnetic minerals in dolentes, limestones and sandstones are titanomagnetite, magnetite and hematite respectively. The rocks were demagnetized thermally and in alternating fields. Vector analysis of the demagnetization path separates the different components of NRM and establishes a characteristic remanence. The paleomagnetic poles for Cretaceous dolentes, Permo-Carboniferous limestones and Lower Devonian sandstones from Spitsbergen, are respectively: λ ′ = 65°N, φ ′ = 222°E, λ ′ = 34°N, φ ′ = 140°E and λ ′=12°N, φ ′ = 135°E. When compared with the European and North American apparent polar wander paths, all Spitsbergen poles he at a distance from both APWPs suggesting that Spitsbergen has been rotated and even translated in relation to Europe during the opening of the Labrador Sea and Greenland-Norwegian Sea.

Origin of magnetic minerals and natural remanent magnetization of basaltic rocks from Lower Silesia, Poland

SummaryTwo groups of basaltic rocks with normal and reversed NRM were examined. It was found that in both groups the primary NRM, synchronous with the period of rock formation, is preserved. Relations of the primary NRM to the origin and the degree of oxidation of magnetic minerals were considered in detail.

Thermomagnetic properties of some Late Mesozoic diabase dikes of South Spitsbergen

SummaryLaboratory investigations of thermomagnetic properties of specimens from seven diabase dikes of South Spitsbergen have been performed. Studies of temperature variation of isothermal saturation remanence combined with Hopkinson effect measurements and investigations of low temperature remanence give information on the mineral composition of the magnetic phases present in the magnetic fraction of the diabases. The experiments show that the ‘clean’ natural remanence of these dikes has been acquired at the time of their, consolidation in the Late Mesozoic, though three of them may have been partially remagnetized at the time of Tertiary orogeny. Since the dikes reveal several normal and reversed directions of ‘clean’ natural remanence, it is concluded that they were formed at different times in the Late Mesozoic, even though some of them may have been subjected to secondary influences at a later date.

Magnetic signature of indoor air pollution: Household dust study

The combination of magnetic and geochemical methods was used to determine the mineralogy, grain size and domain structure of magnetic particles in indoor dust collected in 195 sites in Warsaw, Poland. Data show an asymmetric distribution of magnetic susceptibility (χ) in the wide range of 20–1514 × 10−8 m3 kg−1. Comparison of magnetic parameters shows that the internal dust contains outside pollution characteristic for air and soil. More than 90% of indoor dust samples were characterized by roughly uniform magnetic mineralogy, typical for fine grained magnetite (diameter of 0.2–5 μm), and grain size between pseudo-single-domain and small multi-domain with small contribution of superpara-magnetic particles (∼10%). Samples with χ larger than 220 × 10−8 m3 kg−1 contain mainly magnetite and an anthropogenic metallic Fe with TC > 700°C. The indoor dust contains, characteristic for the urban areas, spherical magnetic particles originated from fossil fuel combustion processes and mixture of irregular angular iron-oxides grains containing other elements, including Na, Ca, Al, Si, K, S, Mn, Cl, and Mg.

Stress dependence of magnetization and magnetic properties of igneous rocks

SummaryThe effect of compression on the magnetization of rocks has been examined for the dependence of the structure on the magnetic fraction and on its composition. The change in magnetization under compression depends on such parameters as coercive force, saturation remanent magnetization, magnetic susceptibility and coercivity.The measurements were carried out for three groups of samples containing three sets of magnetic minerals. The stress dependence of magnetization varies for each group. The dependence of susceptibility and irreversible magnetization on compression was examined. It is revealed that these relations are also different for each group of samples, and depend on the composition of the magnetic fraction and the state of internal stresses.

Paleomagnetism and magnetic mineralogy of metabasites and granulites from Orlica-Śnieżnik Dome (Central Sudetes)

The results of palaeomagnetic, rock magnetic, and microscopic study of Early Paleozoic metabasites and granulites from the OrlicaŚnieżnik Dome (OSD, Sudetes) have been combined with geochronological data. In the eastern part of the OSD (Śnieżnik Massif, SM) ferrimagnetic pyrrhotite is prevalent, accompanied by various amounts of Fe-oxides. In the western part of the OSD (Orlica-Bystrzyca Massif, OBM) Fe-oxides dominate. All magnetic minerals originated during hydrothermal and weathering processes. The palaeomagnetic study revealed the presence of three secondary components of natural remanence: Late Carboniferous, Late Permian, and Mesozoic. Two Paleozoic components are related to volcanic activity in the Sudetes. They are carried by pyrrhotite and Fe-oxides and were isolated only in SM rocks. The Mesozoic component was determined in both parts of the OSD and is carried by Fe-oxides. It covers a time span, from ∼160 to ∼40 Ma, corresponding to a long period of alteration.