ИСТИНА

Experiments on creation of the thermochemical remanent magnetization TCRM on Red Sea basalt samples containing titanomagnetite (TM) with Curie temperature Tc about 200 °C were performed by quick heating to a temperature T* = (450–530) °C followed by a slow cooling in a laboratory magnetic field Blab. A complex of magneto-mineralogical studies was carried out, including electron-microscopic observations, X-ray and thermomagnetic analyzes, measurements of magnetic hysteresis loops at various stages of thermal treatment of the initial samples. It is shown that all samples demonstrate an “explosive” growth of TCRM already at the very beginning of the cooling process, which corresponds to the stage of rapid single-phase oxidation of the initial TM fraction of a basalt so that the process of TCRM acquisition is going due to increase of both Tc and volume of single-phase oxidized regions of TM grains combined with the increase in the volume of titanium depleted (relative to the original TM) of microcells appearing during the subsequent oxidation decomposition. Arai-Nagata diagrams for samples bearing TCRM form a broken line consisting of two rectilinear segments, while the low-temperature interval T<T* corresponds to a mixture of thermochemical and thermoremanent (TRM) magnetizations and gives a slightly overestimated Blab value due to the effect of a low cooling rate, when creating TCRM and TRM. The high-temperature interval is a pure TCRM, and determinations of the intensity Blab for this interval leads to its underestimation by 20-27%. A recommendation is made to reject samples for which two or more straight segments are observed on the Arai-Nagata diagram on background of a one-component NRM.