Potential Bias in Volcanic Paleomagnetic Records Due To Superimposed Chemical Remanent Magnetization

Shcherbakov, V. P.; Lhuillier, F.; Gribov, S. K.; Tselmovich, V. A.; Aphinogenova, N. A. (2024): Potential Bias in Volcanic Paleomagnetic Records Due To Superimposed Chemical Remanent Magnetization. Geophysical Research Letters, 51 (12). ISSN 0094-8276

Abstract

Volcanic rocks, preserving paleorecords of Earth's magnetic field, are essential to constrain the working of the geodynamo, provided their primary signal was not biased. Using a thermomagnetometer, we simulate a situation where a sample's primary record, carried by a thermoremanence (TRM, acquired by cooling in air from 600°C to room temperature), is partly overprinted by a chemical remanence (CRM, acquired by 200 hr of isothermal exposure at 400°C). This situation leads to two directional and intensity components (in the form of linear segments) in the Zijderveld and Arai-Nagata diagrams. In the case of unstable titanomagnetite grains prior to CRM acquisition, we show that both components can be strongly biased by up to ∼50° for paleodirections and ∼50% for paleointensities. In such a worst-case scenario, the secondary CRM strongly overprints the primary TRM, rendering the common interpretation of Zijderveld and Arai-Nagata diagrams in terms of characteristic components invalid.

• Doc-Type: Article (LMU)
• Organisational unit (Faculties): 20 Geosciences > Department of Earth and Environmental Sciences
• DFG subject classification of scientific disciplines: Natural sciences
• DFG: Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - 491502892