15:45h
AN: GP33A-07
TI: NEW INSIGHT INTO THE ORIGIN OF ANOMALOUS MAGNETISM OF TITANOHEMATITE LAMELLAE IN RHOMBOHEDRAL OXIDE ASSEMBLAGES - CONSEQUENCE FOR MARS MAGNETISM
AU: * Kletetschka, G
EM: kletetschka@nasa.gov
AF: Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
AU: * Kletetschka, G
EM: kletetschka@nasa.gov
AF: Department of Physics, Catholic University, 200 Hannan Hall, Washington, DC 20064, United States
AU: * Kletetschka, G
EM: kletetschka@nasa.gov
AF: Institute of Geology, Academy of Sciences, Prague, Czech Republic
AU: Zboril, R
EM: zboril@prfnw.upol.cz
AF: Nanomaterials Research Centre, Palacky Univeristy, Olomouc, Czech Republic
AU: Adachi, T
EM: tomoko.adachi@ssedmail.gsfc.nasa.gov
AF: Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
AU: Adachi, T
EM: tomoko.adachi@ssedmail.gsfc.nasa.gov
AF: Department of Physics, Catholic University, 200 Hannan Hall, Washington, DC 20064, United States
AU: Mikula, V
EM: mikula.vilem@ssedmail.gsfc.nasa.gov
AF: Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
AU: Mikula, V
EM: mikula.vilem@ssedmail.gsfc.nasa.gov
AF: Department of Physics, Catholic University, 200 Hannan Hall, Washington, DC 20064, United States
AU: Hermanek, M
EM: zboril@prfnw.upol.cz
AF: Nanomaterials Research Centre, Palacky Univeristy, Olomouc, Czech Republic
AU: Wasilewski, P J
EM: peter.j.wasilewski@nasa.gov
AF: Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
AB: Remanent magnetization of titanohematite lamellae within oxide assemblages in crustal rocks has been proposed to be a source for intense magnetic anomalies both on Earth as well as Mars. In an attempt to explain the origin of such strong magnetization in titanohematite bearing rocks, two hypotheses have been proposed. First hypothesis (Robinson et al., 2002) proposes a new type of magnetization (lamellar magnetization) associated with the contact zone between the ferrian ilmenite and titanohematite. Second hypothesis proposes that the intense magnetization is a consequence of an "empirical law" related to the low saturation magnetization of titanohematite (Kletetschka et al., 2006). We evaluate these two hypotheses in light of temperature dependent Mossbauer spectra and magnetic measurements. Resulting measurements determine that strong magnetization of titanohematite is due to large canting angle (32 degree from the anti-parallel arrangement) causing ferromagnetic contribution of the titanohematite to the overall magnetization. We also show that the smallest titanohematite lamellae demonstrate blocking temperature near 300C and do not enhance but diminish the overall remanent magnetization. High and low temperature Mossbauer spectra show that titanohematite and ferrian ilmenite are magnetically independent phases and contradict the lamellar magnetism hypothesis coined by Robinson et al., (2002).
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 1519 Magnetic mineralogy and petrology
DE: 1521 Paleointensity
DE: 1540 Rock and mineral magnetism
DE: 1599 General or miscellaneous
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly