HR: 0830h
AN: GP11C-0270    [PDF]
TI: New Paleomagnetic and Rock Magnetic Data From 10-12 Ma Basaltic Cores in ODP Site 1243, Eastern Equatorial Pacific
AU: * Lippert, P C
EM: plippert@es.ucsc.edu
AF: Institute of Geophysics and Planetary Geophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 United States
AU: Zhao, X
EM: xzhao@es.ucsc.edu
AF: Institute of Geophysics and Planetary Geophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 United States
AU: Carlut, J
EM: jcarlut@geologie.ens.fr
AF: Laboratoire de Geologie, Ecole Normale Superieure, 24, rue Lhomond, Paris, 75231 France
AB: We present paleomagnetic and rock magnetic results from samples recovered during ODP Leg 203. Eighty-seven meters of basement rocks were drilled at Site 1243, which is located near a proposed fossil spreading center that became inactive 10-12 Ma. Petrological and geochemical observations distinguish 6 different units within the basement rocks. All units consist of fresh pillow basalts, sometimes with glasses present. Paleomagnetic results indicate that the basaltic cores record a stable component of magnetization with both normal and reversed inclinations after a pervasive drilling-induced remagnetization is removed. The lava sequence recovered at Site 1243 may record a reversal sequence (normal-reversed-normal). Two general types of behavior were found in the rock magnetic measurements of Leg 203 cores. One group has a single phase of Ti-poor titanomagnetite. Basalt samples of this titanomagnetite group exhibit a Verwey transition in the vicinity of 110 K, which is in good agreement with the thermomagnetic characteristics of titanomagnetites with Curie temperatures of ~580§C that were identified. The second group is characterized by more than one Curie temperature, which suggests the presence of multiple magnetic phases. Low temperature curves do not clearly show the Verwey transition. Thermomagnetic signatures indicate the inversion of titanomaghemite to a strongly magnetized magnetite. Variations of Curie temperatures, oxidation state, titanium content, and domain range suggest that a stratigraphically distinct change in magnetic minerals may exist at Site 1243.
DE: 1519 Magnetic mineralogy and petrology
DE: 1533 Remagnetization
DE: 1535 Reversals (process, timescale, magnetostratigraphy)
DE: 3005 Geomagnetism (1550)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting