CHARACTERISTICS OF MAGNETITE IN SUBMARINE BASALTIC GLASS

We have compared the rock-magnetic characteristics of Cretaceous subma rine basaltic glass (SBG) from DSDP/ODP Holes 417D, 418A, 807C and 543 A to data from Holocene glasses from the East Pacific Rise. Both group s are very similar in that they contain single-domain, low-Ti magnetit e as the carrier of a strong and stable remanent magnetization. The be haviour of magnetic hysteresis in SBG is, however, dominated by superp aramagnetic grain-size populations. Transmission electron microscopy r evealed spherically shaped grains of 10-20 nm diameter with crystal la ttice properties consistent with magnetite. These grains could be resp onsible for the magnetic behaviour of SBG.