The dominant magnetic carrier in the SEIR pillow basalts recovered during Leg 187 is titanomaghemite, which presumably formed via low-temperature oxidation (maghemitization) of primary titanomagnetite. Few massive basalt samples contain nearly unoxidized titanomagnetite, indicating that permeability of rocks is a primary controlling factor of maghemitization. The pillow basalts contain titanomaghemite ranging from SSD to PSD grains and are characterized by a single stable component of remanence. The massive basalts contain titanomagnetite that is larger PSD grains.
The NRM values for the SEIR basalts are on the same order as those for other oceanic basalts. They show a general decreasing trend of NRM with crust age from ~14 to ~28 Ma, which reflects an increasing degree of low-temperature oxidation. The magnetic properties, including NRM, of the cored samples recovered from very shallow levels of the pillow layers do not correlate either with tectonic zonations or with mantle provinces of the samples.