Japan Geoscience Union Meeting 2022

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[J] Oral

S (Solid Earth Sciences ) » S-EM Earth's Electromagnetism

[S-EM15] Geomagnetism, paleomagnetism and rock magnetism

Sun. May 22, 2022 10:45 AM - 12:15 PM International Conference Room (IC) (International Conference Hall, Makuhari Messe)

convener:Tetsuro Sato(Earthquake Research Institute, The University of Tokyo), convener:Yutaka Yoshimura(Faculty of Social and Cultural Studies, Kyushu University), Chairperson:Yutaka Yoshimura(Faculty of Social and Cultural Studies, Kyushu University), Chisato Anai(Center for Advanced marine Core Research, Kochi Univercity)

11:15 AM - 11:30 AM

[SEM15-08] High sensitivity and high spacial resolution detection of magnetic material in tree rings using scanning SQUID magnetic microscope

*Hirokuni Oda1 (1.Institute of Geology and Geoinformation, Geological Survey of Japan, AIST)

Keywords:red pine, scanning SQUID magnetic microscope, low temperature magnetometry

We conducted magnetic imaging on a red pine tree using scanning SQUID microscope. Thin sections were prepared with a thickness of about 1 mm from a tree trunk of a red pine containing the part close to the bark. Magnetic field values measured on thin sections were very weak typically less than about 0.2 nT. After exposing to a vertical magnetic field of 2T, surface magnetic fields of a few nT were observed as stripes parallel to the annual growth rings. Areas with strong magnetic field correspond to spring layers with high growth rate composed of less dense material. Spring layer has reddish brown spots, which shows dipole magnetic anomalies. These might be isolated magnetic mineral grains contained in the tree. Low temperature magnetometry conducted on a sample from the tree trunk suggest that there are two mineral phases with distinct magnetic phase transition temperatures of 65K and 105K. The higher transition temperature might be Verwey transition of magnetite with some impurities or non-stoichiometry. In the presentation, we discuss possible origins of the magnetic minerals based on magnetic microscopy and rock magnetism as well as element mapping using X-ray Fluorescense.