Fig. 8

a Log–log plot of magnetic susceptibility (K; SI) and natural remanent magnetization (NRM; A/m) of basaltic lava samples collected near the Kairei and Yokoniwa hydrothermal fields of the Central Indian Ridge. The broken lines show constant Q values (Koenigsberger ratio) calculated for a magnetic field of 45,000 nT. The red circles show averaged values with standard deviations in each lava sample and the gray circles show each measured value for all cubic specimens. b Comparison between reliable magnetic-anomaly-derived absolute magnetization (MADAM) with high coherency (> 0.5 and > 0.3 for 918R06) and NRM measured on rock samples. The applied MADAM corresponding to each rock NRM intensity was the average value near each rock sampling location (within 100 m). The error bars along the x- and y-axes show standard deviations of the NRM intensities and MADAM estimates for each point, respectively. The red circles show the data of the Central Indian Ridge (CIR) presented in this study. The green squares and blue triangles show previously reported data from the southern Mariana Trough (Fujii et al. 2015) and Mid-Atlantic Ridge (Honsho et al. 2009), respectively