The role of secondary magnetization for determining the characteristic component and paleointensity in basaltic rocks in which the carrier of remanent magnetization is titanomagnetite of varying oxidation states is assessed. For this purpose, laboratory experiments were performed on basalt from the Reykjanes underwater ridge (North Atlantic) to create the “primary” total thermoremanent magnetization TRM (formed after holding the samples at 600°C for some time with subsequent cooling in a magnetic field of 50 µT) and the «secondary» chemical remanent magnetization CRM perpendicular to it (imposed during subsequent 200-hour exposure at 350°C in the field of the same size). The time monitoring of changes in the TRM and CRM components was carried out directly at the temperature of 350°C. The liler experiments were performed on samples with laboratory-generated total remanent magnetizations, and the results were used to construct Arai–Nagata and Zijderveld diagrams. It was shown that CRM is formed on new ferrimagnetic phases resulting from the oxidation of the unstable titanomagnetite fraction, and its intensity critically depends on the oxidation state of the original material. In all the obtained diagrams, differently inclined linear segments are distinguished in the following intervals: low-temperature (LT) from 20–350°C to 450°C, medium-temperature (MT) from 450–475°C to 500–530°C, and high-temperature (HT) from 500–530°C to 560–600°C. It is shown that the presence of a secondary component leads to errors in determining both paleodirection and paleointensity based on the primary component, and these errors are the greater, the larger the secondary CRM is in relation to the primary TRM. A new criterion for the reliability of paleomagnetic data is proposed, which applies to both paleointensity and paleodirections: the secondary component should be several times smaller in magnitude than the primary one.
S. K. Gribov (Wed,) studied this question.