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Nanopaleomagnetism of meteoritic Fe-Ni studied using X-ray photoemission electron microscopy

DOI: 10.1016/j.epsl.2014.04.016 DOI Help

Authors: James Bryson (University of Cambridge) , Julia Herrero-Albillos (Fundación ARAID; Centro Universitario de la Defensa; CSIC – Universidad de Zaragoza) , Florian Kronast (Helmholtz Zentrum Berlin) , Massimo Ghidini (University of Cambridge; DiFeST, University of Parma) , Simon A. T. Redfern (Department of Earth Sciences, University of Cambridge) , Gerrit Van Der Laan (Diamond Light Source) , Richard J. Harrison (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Earth And Planetary Science Letters , VOL 396 , PAGES 125 - 133

State: Published (Approved)
Published: June 2014

Open Access Open Access

Abstract: X-ray photoemission electron microscopy (XPEEM) enables natural remanent magnetisation to be imaged with resolution across a field of view of 5–20 μm. The method is applied to structural features typical of the Widmanstätten microstructure (kamacite – tetrataenite rim – cloudy zone – plessite) in the Tazewell IIICD iron meteorite. Kamacite lamellae and the tetrataenite rim are multidomain, whereas plessite consists of laths of different phases displaying a range of stable magnetisation directions. The cloudy zone (CZ) displays a complex interlocking domain pattern resulting from nanoscale islands of tetrataenite with easy axes distributed along three possible crystallographic directions. Quantitative analysis of the coarse and intermediate CZ was achieved using a combination of image simulations and histogram profile matching. Remanence information was extracted from individual regions of interest wide, demonstrating for the first time the capability of XPEEM to perform quantitative paleomagnetic analysis at sub-micron length scales. The three tetrataenite easy axis orientations occur with equal probability in the coarse and intermediate CZ, suggesting that spinodal decomposition in these regions was not strongly influenced by internal interaction fields, and that they are suitable candidates for future paleomagnetic studies. The fine CZ shows a strong dominance of one easy axis. This effect is attributed to island–island exchange interactions that render the fine CZ unsuitable for paleomagnetic study. Variations in the relative strength (proportion of dominant easy axis) and direction (direction of dominant easy axis) of a paleomagnetic field can be resolved from different regions of the CZ using XPEEM, raising the prospect of obtaining a time-resolved measurement of the active dynamo period in meteorites originating from the upper unmelted regions of differentiated asteroids (e.g. chondrites, pallasites, mesosiderites).

Journal Keywords: extraterrestrial magnetism; tetrataenite; cloudy zone; high-resolution magnetic microscopy; X-ray photoemission electron microscopy; meteorites

Diamond Keywords: Meteorites

Subject Areas: Earth Science, Physics, Technique Development

Facility: BESSY II

Added On: 27/09/2014 15:08


Discipline Tags:

Technique Development - Earth Sciences & Environment Earth Sciences & Environment Physics Magnetism Geology Planetary Geology

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