Sample Ms Mr Bc Bcr Mr/Ms Bcr/Bc B2861 1.21 0.267 11.63 21.02 0.221 1.807 B4591 0.34 0.14 29.25 41.7 0.412 1.426 B5981 1.3 0.2 6.79 12.94 0.154 1.906 B7151 0.95 0.113 3.29 6.24 0.119 1.897 Image credit: IODP, Blastcube from wiki AF Thermal Can we use field dependence of susceptibility to identify the magnetic mineralogy of submarine basalts? Hong Yang (hyang777@Stanford.edu), Sonia M. Tikoo | Dept of Geophysics/Dept of Earth & Planetary sciences, Stanford University Dario Bilardello, Peat Solheid | Institute for Rock Magnetism, University of Minnesota IODP Expedition 391 scientists 30-second Summary Background & Motivation Sample Info χHd = (χ300 A/m -χ30 A/m)/χ30 A/m -100 x10 -3 -50 0 50 100 0.16 0.12 0.08 0.04 0.00 Bc (T) 600 400 200 0 -200 -400 -600 Am 2/T 2 Bu (T) -100 x10 -3 -50 0 50 100 0.12 0.08 0.04 0.00 Bc (T) 400 300 200 100 0 Am 2/T 2 Bu (T) -100 x10 -3 -50 0 50 100 0.12 0.08 0.04 0.00 Bc (T) 2500 2000 1500 1000 500 0 -500 Am 2/T 2 Bu (T) 𝜒= 1% 𝜒= 5% 𝜒= 51% 𝜒= 14% -100 x10 -3 -50 0 50 100 0.16 0.12 0.08 0.04 0.00 Bc (T) 600 400 200 0 -200 Am 2/T 2 Bu (T) T (℃) k (10-6 SI) k (10-6 SI) T (℃) k (10-6 SI) T (℃) k (10-6 SI) T (℃) Preliminary Conclusions Acknowledgement References heating cooling heating cooling heating cooling heating cooling To help guide the choice of demagnetization method of submarine basalts in shipboard/lab measurements, we test if room temperature field dependence can be used to infer the magnetic mineralogy of submarine basalts. We studied magnetic properties of basalts with different field dependences. We found the field dependence behavior is associated with Hopkinson peaks. High field-dependent basalts are characterized by reversible thermomagnetic curves and low Curie temperature and should be better treated with AF demagnetization. [1] Zhou W, Van der Voo R, Peacor D R, Zhang Y 2000 Earth Planet. Sci. Lett. 179 9 [2] Özdemir Ö 1987 Phys. Earth Planet. Inter. 46 184 [3] Furuta T 1993 Geophys. J. Int. 113 95 [4] Sager W, Hoernle K, Petronotis K 2020 [5] Jackson M, Moskowitz B, Rosenbaum J, Kissel C 1998 Earth Planet. Sci. Lett. 157 129 [6] Bilardello D 2023 IRM Q. 32-4 [7] Clark D A 2016 ASEG Extended Abstracts 2016 1 Field dependence data: Clark 2016 B2861 Deposit type: pillow lava Depth: 292.52m Location: (-32.32806, -0.643127) B5981 Deposit type: massive lava flow Depth: 391.32 m Location: (-32.32806, -0.643127) B4591 Deposit type: massive lava flow Depth: 174.09 m Location: (-25.202398, 7.4969) B7151 Deposit type: massive lava flow Depth: 181.92 m Location: (-25.202398, 7.4969) • Field-dependent behavior is associated with the Hopkinson peak, especially the rising part. • Real and Imaginary susceptibilities show different peak positions • The magnitude of room temperature field dependence depends on where the Hopkinson peak is, which is influenced by the Ti content of Titanomagnetite. • Samples with high field dependence is correlated with low Curie temperature and reversible k-T curve. They are better suited for AF demagnetization. • More to explore with field-frequency dependence? • We thank Institute for Rock Magnetism for awarding HY the visiting student fellowship to conduct this research. Additionally, we would like to extend our appreciation to Max Brown for his valuable assistance in arranging the visit. • The IRM is a US National Multi-user Facility supported through the Instrumentation and Facilities program of the National Science Foundation, Earth Sciences Division (NSF EAR -2153786), and by funding from the University of Minnesota.”