HR: 1340h
AN: GP13A-0029    [Abstracts]
TI: Characterization of Titanomagnetites and Titanomaghemites From Lavas of the Southern Volcanics, Chatham Islands, New Zealand
AU: * Brown, H
EM: holly@earth.rochester.edu
AF: University of Rochester, Department of Earth & Environmental Sciences 227 Hutchison Hall, Rochester, NY 14627 United States
AU: Mason, S
EM: steph@earth.rochester.edu
AF: University of Rochester, Department of Earth & Environmental Sciences 227 Hutchison Hall, Rochester, NY 14627 United States
AU: Ebsary, W
EM: bill@earth.rochester.edu
AF: University of Rochester, Department of Earth & Environmental Sciences 227 Hutchison Hall, Rochester, NY 14627 United States
AU: Bauch, D
EM: bauch@earth.rochester.edu
AF: University of Rochester, Department of Earth & Environmental Sciences 227 Hutchison Hall, Rochester, NY 14627 United States
AU: Cottrell, R D
EM: rory@earth.rochester.edu
AF: University of Rochester, Department of Earth & Environmental Sciences 227 Hutchison Hall, Rochester, NY 14627 United States
AU: Tarduno, J A
EM: john@earth.rochester.edu
AF: University of Rochester, Department of Earth & Environmental Sciences 227 Hutchison Hall, Rochester, NY 14627 United States
AU: Sutherland, R
EM: r.sutherland@gns.cri.nz
AF: Institute of Geological & Nuclear Sciences, PO Box 30-368 Lower Hutt, Wellington, 6315 New Zealand
AU: Campbell, H
EM: h.campbell@gns.cri.nz
AF: Institute of Geological & Nuclear Sciences, PO Box 30-368 Lower Hutt, Wellington, 6315 New Zealand
AB: As we seek increasingly better resolution of the paleomagnetic record, it is clear that a more thorough rock magnetic characterization is needed of many rock units. Many analytical techniques, once thought exceptional, are now standard, and we have new insights into the nature of magnetic domains available through years of careful experimental and theoretical work. In particular, David Dunlop has made seminal contributions that have advanced the discipline of rock magnetism; we are all fortunate to have the text Rock Magnetism: Fundamentals and frontiers by David and Özden Özdemir to serve as a guide. One rock unit that merits rock magnetic characterization is the Late Cretaceous Southern Volcanics of the Chatham Islands (New Zealand). These islands are the subaerial part of the much larger Chatham Rise which is a far southern portion of the Pacific plate. Paleomagnetic data from the Southern Volcanics hold the potential to investigate topical tectonic issues, including the motion of hotspots. In a classic study, Grindley et al. (1979) reported on the age and paleomagnetism of these rocks, but only low peak alternating demagnetization fields were employed. Here we report new rock magnetic data from these lavas. Magnetic susceptibility data versus temperature were collected with a KLY-4S Kappabridge. Some lavas are dominated by magnetic populations with very low Curie points (< 200 ^oC), whereas other samples have higher values (400-500 ^oC). Only a few samples show evidence for the Verwey transition. Some flows and dikes exhibit increases in magnetic susceptibility with heating, which probably reflect maghemitization; others show no evidence for inversion. These analyses, together with preliminary SEM data yield little evidence for high temperature oxidation. We will report SEM-EDS and XRD data to constrain the oxidation parameters typical of the Southern Volcanics. We will also report rock magnetic data (low temperature and FORC results) collected on plagioclase crystals separated from the lavas.
DE: 1519 Magnetic mineralogy and petrology
DE: 1520 Magnetostratigraphy
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005