Fig. 3: Magnetic hysteresis.
Magnetic hysteresis results for a seafloor white pumice b Havre white raft pumice and c pink raft pumice with d–f close ups of the origin of the magnetic hysteresis results highlighting subtle differences in magnetic remanence (MR) and coercivity (HC) between the different pumice types. A combination of magnetic parameters (Supplementary Table S3) and frequency dependence of magnetic susceptibility (χfd) are utilized to determine that the white and pink raft pumice hysteresis loops represent a mixture of superparamagnetic (SP) < 10 nm and MD magnetite grains, and that seafloor white pumice contains purely MD magnetite. In addition, c, f Havre pink raft pumice displays a classic wasp-waisted hysteresis signature closing past 0.6T suggesting that both magnetite and hematite are present51. Duplicates for white and pink raft pumice sample type show similar results as displayed here, while limited material of white seafloor pumice allowed for only one analysis.
