HR: 1340h
AN: GP43A-0886    [Abstracts]
TI: Magnetic Paleofield of Avanhandava H4 Chondrite's Matrix and Chondrules - Implications on Magnetic Fields in Early Solar System.
AU: * Kohout, T
EM: tomas.kohout@helsinki.fi
AF: Division of Geophysics, Faculty of Science, University of Helsinki, P.O. Box 64, Helsinki, 00014 Finland
AU: * Kohout, T
EM: tomas.kohout@helsinki.fi
AF: Department of Applied Geophysics, Faculty of Science, Charles University in Prague, Albertov 6, Prague, 12843 Czech Republic
AU: * Kohout, T
EM: tomas.kohout@helsinki.fi
AF: Institute of Geology, Academy of Sciences of the Czech Republic, Rozvojova 135, Prague, 16500 Czech Republic
AU: Pesonen, L J
EM: lauri.pesonen@helsinki.fi
AF: Division of Geophysics, Faculty of Science, University of Helsinki, P.O. Box 64, Helsinki, 00014 Finland
AB: The Avanhandava (H4) fall occurred in 1952 in Brazil. A total of 9.33 kg had been preserved after the meteorite brake up during the impact [1]. The meteorite contains large (0.1 - 2.0 mm) chon-drules that have clearly delineated boundaries with matrix. This characteristic allows us to pick up oriented individual chondrules and study their magnetic properties. The chondrules of the Avanhandava meteorite show a low and randomly oriented NRM (10-2 - 10-1 mAm2/kg). In contrast the matrix is strongly (100 - 101 mAm2/kg) and uniformly magnet-ized [2]. Various methods for paleofield determination have been applied on matrix and individual chondrules in order to determine possi-ble magnetizing processes and paleofields in early solar systems.. The laboratory experiments reveal approximate paleofields for matrix similar to present geomagnetic field. The paleofield de-termined for chondrules is approximately one order of magnitude lower comparing to values obtained for matrix. That suggests that chondrules are not magnetically contaminated by geomagnetic or artificial fields and they acquired their NRM prior their aggregation to Avanhandava parent body (random NRM directions). The matrix shows remarkable traces of terres-trial weathering and is uniformly magnetized. The paleofield re-sult for matrix indicates possible remagnetization caused by ter-restrial weathering. The terrestrial weathering of ordinary chon-drites is observed even on falls stored in museums and can sig-nificantly influence meteorite magnetic records [3, 4]. References: [1] Paar W. et al. 1976. Revista Brasileira de Geo-ciencias 6: 201-210. [2] Kohout T. and Pesonen L. J. 2005. 68th Annual Meteoritical Society Meeting: 5202. [3] Kohout T. et al. 2004. Physics and Chemistry of the Earth 29: 885-897. [4] Lee M. R. and Bland P. A. 2004. Geochimica et Cosmochimica Acta 68: 893-916.
UR: http://www.volny.cz/tomkohout/meteo/
DE: 1521 Paleointensity
DE: 1533 Remagnetization
DE: 1540 Rock and mineral magnetism
DE: 6205 Asteroids
DE: 6240 Meteorites and tektites (1028, 3662)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005