[S-CG48] Ocean Floor Geoscience

[SCG48-P26] Paleomagnetic analysis of deep-sea pillow basalt oriented by a cross-line laser installed on the Shinkai 6500.

*Jun Shibuya¹, Tatsuo Kanamaru¹, Kuniyuki Furukawa², Kenichiro Tani³, Yuhji Yamamoto⁴ (1.Nihon University, 2.Aichi University, 3.National Museum of Nature and Science, 4.Kochi University)

Keywords:Shinkai 6500, Oriented rock sample, cross-line laser, paleomagnetism

Paleomagnetic studies using oriented rock samples play an important role in the development of Earth science, including the elucidation of plate tectonics, among other aspects. However, obtaining oriented rock samples from the deep-sea floor has been notably challenging due to technical difficulties, with few exceptions such as the work by Ueda et al., whereas obtaining an oriented terrestrial sample can be relatively easy using instruments such as a clino-compass. Although many researchers have investigated the sampling method (e.g., Yamazaki et al., 2021, EPS; Cogné et al 1995, EPSL; Hurst and Karson, 1994, Tectonics), a consistent method has not yet been established due to various constraints. We successfully collected oriented rock samples, including pillow basalt and pumice, from submarine volcanoes using a cross-line laser installed on the Shinkai 6500 during cruise YK23-16S. For a detailed description of the sampling process, see Furukawa et al. (2024, JpGU). By conducting stepwise thermal demagnetization experiments, we obtained the characteristic remanent magnetization (ChRM) of pillow basalts. The ChRMs exhibit multiple linear components that are consistent with the present-day north. The average declination of the low-temperature components of the ChRMs is weakly concentrated around geographic north or slightly east, and the average inclination is slightly shallower than the angle expected from the latitude, assuming a geocentric dipole magnetic field. The presence of multiple components of ChRM in the pillow basalt suggests that it may record tilting during the cooling of the basalts.