Rotational remanent magnetization as a magnetic mineral diagnostic tool at low rotation rates

SUMMARY Prior work on rotational remanent magnetization (RRM) and anhysteretic (ARMROT) has demonstrated promise for magnetic mineral identification in earth materials. One challenge been to calibrate the measurements types microstructural controls, since previous studies have used differing spin rates, alternating field (AF) intensities decay times, which hinders a comparison of data sets. Using RAPID magnetometer we show that range usable practical rotation rates is 0.25–3 Hz [rps] allows wide RRM ARMROT characteristics be utilized (at 100 mT AF field, μT bias field). Sets extracts from sediments, well characterized rock samples contain key minerals magnetite, pyrrhotite greigite are calibration RRM-ARMROT behaviour. Detrital pyrrhotite-bearing phyllites largely small positive effective (Bg) values (up 6 μT), with differences Bg ratios at 0.5 2.5 allowing grain size discrimination. The values, changes allow distinction magnetite diagenetic greigite. Diagenetic –83 –109 [rps]) unusual variation low caused by anisotropy affects. In contrast work, based crushed sized natural high single domain intact bacterial magnetofossils Upper Cretaceous Chalk some lowest (0–1 μT) displays steep decline increasing rates. A simple tool particle characterization may ratio [rps]. Stability better studied using acquisition intensity, static demagnetization imparts nuisance gyroremanence along axis. Mineral microstructure, dislocations interactions likely additional effects behaviour need more investigation.