FOLCO, LUIGI

Gattacceca J

PERCHIAZZI, NATALE

Rochette P

English

Archivio della Ricerca - Università di Pisa

A NEW MICROMETEORITE COLLECTION FROM ANTARCTICA AND ITS PRELIMINARY CHARACTERI-ZATION BY MAGNETIC METHODS. P. Rochette1, J. Gattacceca1, L. Folco2 and N. Perchiazzi.3 1CEREGE, Aix-en-Provence, France (rochette@cerege.fr). 2Museo Nazionale Antartide, Siena, Italy., 3University of Pisa, Italy.  Introduction: In December 2003, the meteorite recovery party of the XIX PNRA expedition collected by magnetic extrac-tion thousands of micrometeorites in the 100-800 µm size range in an aeolian deposit at the top of Frontier Mountain (northern Victoria Land, Antartica), a few Myr old glacially eroded surface. This discovery, located by the use of a magnetic gradiometer, offered a good opportunity to test and develop a magnetic classi-fication procedure for these objects, in parallel to "classical" min-eralogical and geochemical characterization. After SEM imaging (see figure), magnetic measurements were performed on individual particles with diameter above 400 µm. EDAX detectable Ni and Cr contents of the particles confirm their extraterrestrial origin. Hysteresis loop parameters, magnetic susceptibility and demagnetization of isothermal remanence at saturation were obtained on single particles.   Backscattered SEM images of four micrometeorites collected at Frontier Mountain. Scale bar is 200 µm, 100 µm for lower left picture.  Preliminary results: The magnetic measurements allow the discrimination of at least four distinct populations of particles. The largest population contain about 10 wt. % magnetite. An-other population contains around 2 w% magnetite in much smaller grains, likely concentrated in the external crust. The lower left particle in figure is  dominantly made of Fe,Ni metal and a C-bearing phase.  Perspectives: Microprobe and noble gas analyses will be performed on these micrometeorites. The results will be com-pared to the magnetic classification in order to evaluate its accu-racy and usefulness. If validated, the non-destructive and rapid magnetic classification will be applied to a large number of mi-crometeorites in order to compare the Frontier Mountain collec-tion with other micrometeorite collections (e.g. the South Pole [1] or the Cap Prudhomme [2] collections). References: [1] Taylor S. et al. 2000. Meteoritics & Plane-tary Science 35:651-666. [2] Maurette M. et al. 1991. Nature 351:44-47.  67th Annual Meteoritical Society Meeting (2004) 5026.pdf

A new micrometeorite collection from Antarctica and its preliminary characterization by magnetic methods

https://arpi.unipi.it/bitstream/11568/90476/1/Rochette_5026_2004.pdf

A new micrometeorite collection from Antarctica and its preliminary characterization by magnetic methods

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