HR: 1340h
AN: MR33A-0147    [Abstracts]
TI: Magnetic Field Visualization of Magnetie From Skarns and Serpentinites Using Magneto-Optical Imaging
AU: * Bobyl, A
EM: bobyl.theory@mail.ioffe.ru
AF: Physics of Geological Processes (PGP), University of Oslo, P. O. Box 1048 Blindern, 0316 Oslo, Norway, Oslo, 0316 Norway
AU: * Bobyl, A
EM: bobyl.theory@mail.ioffe.ru
AF: A.F.Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, St.Petersburg 194021, Russia, St.Petersburg, 194021 Russian Federation
AU: Podladchikov, Y
EM: iouri.podladtchikov@fys.uio.no
AF: Physics of Geological Processes (PGP), University of Oslo, P. O. Box 1048 Blindern, 0316 Oslo, Norway, Oslo, 0316 Norway
AU: Austrheim, H
EM: hakon.austrheim@geo.uio.no
AF: Physics of Geological Processes (PGP), University of Oslo, P. O. Box 1048 Blindern, 0316 Oslo, Norway, Oslo, 0316 Norway
AU: Jamtveit, B
EM: bjorn.jamtveit@geo.uio.no
AF: Physics of Geological Processes (PGP), University of Oslo, P. O. Box 1048 Blindern, 0316 Oslo, Norway, Oslo, 0316 Norway
AU: Johansen, T
EM: t.h.johansen@fys.uio.no
AF: Department of Physics, University of Oslo, P. O. Box 1048 Blindern, 0316 Oslo, Norway, Oslo, 0316 Norway
AU: Shantsev, D
EM: daniil.shantsev@fys.uio.no
AF: Department of Physics, University of Oslo, P. O. Box 1048 Blindern, 0316 Oslo, Norway, Oslo, 0316 Norway
AB: Magneto-optical imaging based on the Faraday-effect has been used to characterize magnetic minerals embedded in a nonmagnetic matrix. We have studied magnetite grains and magnetite-magnetite grain boundary regions in samples of skarns and serpentinites. The spatial distributions of the perpendicular component of the remanent magnetic field were measured at the surfaces of polished thin sections with 1 μm spatial resolution, after applying a magnetic field of 50-160 mT at room temperature. The magneto-optical images directly reveal the shape and arrangement of magnetite grains in a simple way. The sensitivity and resolution of the imaging technique is maximized when images captured for two opposite directions of grain magnetizations are subtracted to produce a new `difference image'. The method potentially can resolve grain arrangement, intra-grain heterogeneities in magnetic properties, and grain boundaries down to a scale of about 200 nm. The measured distributions allow us to identify magnetite grains, particles and stripes as well as complex intracrystalline spatial arrangement of magnetic domains within individual magnetite grains. Quantitative analysis of the coercive field dependencies on the magnetite grain sizes or stripe width shows that they cannot be understood without proper account of the internal domain structure, chemical contents or thinsection fabrication procedure.
DE: 1519 Magnetic mineralogy and petrology
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
DE: 8030 Microstructures
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005