Open AccessThe detection of single‐domain greigite (Fe 3 S 4 ) using rotational remanent magnetization (RRM) and the effective gyro field (Bg): mineral magnetic and palaeomagnetic applications
Author(s) -
Snowball Ian F.
Publication year - 1997
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1997.tb01865.x
Subject(s) - greigite , magnetite , remanence , natural remanent magnetization , ferrimagnetism , geology , mineralogy , single domain , magnetization , nuclear magnetic resonance , analytical chemistry (journal) , magnetic domain , magnetic field , chemistry , physics , quantum mechanics , paleontology , chromatography
SUMMARY The intensity of rotational remanent magnetization (RRM) acquired by single‐domain greigite at a rotation frequency of 5 rps was combined with measurements of anhysteretic remanent magnetization (ARM) to calculate the effective biasing field ( Bg ) that produced the RRM. Samples of single‐domain greigite had Bg values between ‐137 and ‐84 μT, and a MDF RRM of c. 80 mT. By contrast, a suite of natural and synthetic ferrimagnetic iron oxide samples, including single‐domain magnetite and y Fe 3 O 4 tape particles, acquired Bg values between ‐3 and ‐14 μT, and MDF RRM ranged between 43 and 68 mT (when RRM was acquired). Multidomain magnetite did not acquire a RRM. Bg values at 5 rps were calculated from previously published data for magnetite particles of different grain sizes, which revealed a minimum Bg value of ‐24 μT and a MDF RRM of 57 mT for the finest fraction (0.2‐0.8 μm in diameter). In a geological example, measurements of Bg and MDF RRM were used to detect the presence of greigite in a 4 m long Late Weichselian sediment core. Variations in inclination, declination and the intensity of the natural remanent magnetization (NRM) correlate with changes in magnetic mineralogy.