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