A New Original Conception in Rock Magnetism, Paleomagnetism and Geomagnetism: An Origin of the Reversed Magnetization of Rocks on Earth

• Published in: Contributions to geophysics & geodesy 2018-03, Vol.48 (1), p.75-112
• Main Author: Orlickỳ, Oto
• Format: Article
• Language: English
• Subjects: exchange interactions; The Fe-Ti FriM-AFM cubic and tetragonal spinels; the fe-ti frim-afm cubic and tetragonal spinels, exchange interactions, weiss molecular field, the reversed magnetization of rocks; the reversed magnetization of rocks; Weiss molecular field
• ISSN: 1338-0540; 1338-0540
• DOI: 10.2478/congeo-2018-0003

So far the field-reversal theory has been accepted to account for the reversed remanent magnetization (RM) of rocks on the Earth. Orlickỳ (2014) revealed a frequent occurrence of the antiferromagnetic (AFM) Fe-Ti oxides in the rocks. Now I have renamed these minerals as the Fe-Ti ferrimagnetic-antiferromagnetic chemical phases (Fe- Ti FriM-AFM ChPs). They may have either cubic spinel, or tetragonal spinel symmetry, respectively. They behave as the Fe-Ti polycrystalline materials. These Fe-Ti FriMAFM ChPs are the two sublattice A and B ChPs, with some specific magnetic behaviour. The titanomagnetite (Ti-Mt, Curie temperature, TC = 230 C; FriM alignment) and the titanomaghemite (Ti-Mgh, Néel temperature, TN = 450 C; AFM alignment) containing rocks have been identified as the representants of the the Fe-Ti FriM-AFM cubic spinel ChPs. The interactions with the magnetizing field, with the Weis molecular fields (Weiss-Heisenberg forces) have generated the reversally oriented internal field. The reversally oriented spontaneous magnetization has arosen in the rock. This internal field has been identified as the most important phenomenon leading to the production of the reversally oriented magnetization in the Fe-Ti FriM-AFM ChPs containing rocks. The equations expressing the magnetic behaviour of the magnetic susceptibility (κ) of rocks versus temperature have been derived. The Fe-Ti FriM-AFM cubic spinel can undergone the transition in favour of the Fe-Ti FriM-AFM tetragonal spinel in the rocks, due to a change of the thermodynamic conditions in nature. The reversed RM has supposed been inparted from the Fe-Ti FriM-AFM cubic spinel during this alteration-transition processess. Such tetragonal spinel is more stable and it is able to survive in the rocks in nature. The results of laboratory magnetization of the selected groupings of rocks have been presented below. The basic laboratory methods for the detection of the magnetic behaviour of the Fe-Ti FriM-AFM ChPs containing rocks are described as well. The presented results have shown that we do not need to apply the field reversal theory, because I have revealed the realistic mechanism which is able to generate the reversed RM of rocks under a presence of the normal geomagnetic field.