[S-CG48] 海洋底地球科学

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

*澁谷 純¹、金丸 龍夫¹、古川 邦之²、谷 健一郎³、山本 裕二⁴ (1.日本大学、2.愛知大学、3.国立科学博物館、4.高知大学)

キーワード：しんかい6500、定方位岩石試料、クロスラインレーザー、古地磁気学

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.