Paleomagnetic investigation of seamounts in the vicinity of Ogasawara Fracture Zone northwest of the Marshall Islands, western Pacific

Abstract

Nine seamounts located northwest of the Marshall Islands near the Ogasawara Fracture Zone were inverted for their uniform magnetization using total field magnetic anomaly and detailed bathymetric data. The paleomagnetic poles of most of the seamounts in our study area generally cluster around the Pacific Apparent Polar Wander Path (APWP). However, those that deviate significantly from the APWP are located south of the fracture zone. The seamounts in our study area can also be divided into two groups on the basis of complexity of the observed magnetic field anomaly. In general, simple conical seamounts exhibit a dipole-like field anomaly pattern with a paired anomaly low and high, and can be explained to a large extent by a uniformly magnetized source. On the other hand, those with complex morphology are larger in size, show multiple magnetic lows and highs and lie very close to or within the fracture zones, suggesting that they were formed by multi-stage volcanism.