46. MAGNETIC PROPERTIES OF BASALT SAMPLES FROM HOLES 504B AND 505B ON THE

More than 60 basalt samples from two Deep Sea Drilling Project holes on the Costa Rica Rift were studied for mag-netic properties and were found to have no properties significantly different from other DSDP basalts. Opaque min-eralogical and thermomagnetic properties of these samples, however, to some extent show differences from normal sub-marine basalts; a new type of thermomagnetic curve and wide range of chemical compositions were recognized. Oxi-dized samples possibly containing incipient ilmenite exsolution lamellae were reduced and re-equilibrated during heating. The Curie temperatures of the re-equilibrated titanomagnetites are interpreted to be those of the original crystallized phase before oxidation