TRM Acquisition in Titanomagnetite Under Lower Crustal Pressures
Abstract
The geological sources of large-scale lithospheric magnetic field anomalies are poorly constrained. Understanding the magnetic behavior of rocks (and their magnetic minerals) under the pressures and temperatures encountered in the Earth's crust is particularly important in that task. While this behavior is rather well constrained for crustal temperatures, the impact of high crustal pressures is not so well known, and therefore is most of the time neglected in numerical models of the geological sources of magnetic anomalies. We present thermal remanent magnetization (TRM) acquisition, and stepwise thermal demagnetization on synthetic titanomagnetite [1] dispersed powder, under pressure up to 0.9 GPa. We used an amagnetic high-pressure cell capable of transforming an applied monoaxial pressure into a hydrostatic pressure up to 2 GPa measured within the cryogenic magnetometer after thermal cycling [2]. We observed pressure-dependent increase in the Curie temperature (initially in the 50-70°C range), mostly between 0.3 and 0.6 GPa, of the order of 20 K/GPa. TRM intensity also increases with pressure although the pressure variation with temperature inside the cell complicates the interpretation. [1] Lattard, D., et al. (2006) J. Geophys. Res., 111, B12S28, doi: 10.1029/2006JB004591; [2] Bezaeva N.S. et al. (2015) Geophys. Res. Lett. 42, doi:10.1002/2015GL066306.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMGP22A..05L
- Keywords:
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- 1518 Magnetic fabrics and anisotropy;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1519 Magnetic mineralogy and petrology;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1540 Rock and mineral magnetism;
- GEOMAGNETISM AND PALEOMAGNETISM