Magnetic properties of biogenic soil greigite (Fe₃S₄)

Abstract

Magnetic measurements were performed on soil samples, which contained bacterial greigite. The greigite‐containing soil horizon is characterized by SIRM/χ > 70 kA m −1 and by Q‐factors >5. Alternating field (AF) demagnetization curves of the NRM gave stable directions. According to IRM acquisition and alternating field demagnetization of the IRM and ARM, the greigite in bulk soil samples shows single domain behaviour. This SD behaviour is also confirmed by hysteresis and by frequency‐dependent susceptibility measurements. The thermomagnetic behaviour was checked on extracted greigite. The magnetic parameters of soil greigite are compared with parameters of sedimentary greigite and of bacterial magnetite.