Modeling Magma Intrusion-Induced Oxidation: Impact on the Paleomagnetic TRM Signal in Titanomagnetite

Low-temperature oxidation of titanomagnetite in oceanic basalts distorts the primary thermoremanent magnetization (TRM) signal essential for reconstructing Earth’s magnetic field history, though the specific impact of magma intrusion-induced oxidation on paleointensity preservation remains poorly constrained. This investigation simulates such oxidation processes through isothermal annealing (260 ◦C; 50 μT field; durations 12.5–1300 hours) of Red Sea rift basalts (P72/4), employing the Thellier-Coe method to quantify how chemical remanent magnetization (CRM) overprinting affects TRM fidelity under controlled field orientations aligned either parallel or perpendicular to the initial TRM. Results demonstrate bimodal Arai-Nagata plots with reliable TRM preservation below 360 ◦C but significant alteration artifacts above this threshold. Crucially, field orientation during oxidation critically influences accuracy: parallel configurations maintain fidelity (±3% deviation at Z = 0.48), while perpendicular fields introduce systematic biases (38% overestimation at Z = 0.15; 20% underestimation at Z > 0.48), attributable to magnetostatic interactions in core-shell grain structures. These findings establish that paleointensity reliability in oxidized basalts depends fundamentally on the alignment between oxidation-era magnetic fields and primary TRM direction, necessitating stringent sample selection and directional constraints in marine paleomagnetic research to mitigate CRM-TRM interference.