[meteorite-list] Geophysics, meteorites, and Electron microscopy

[Carl Agee]

A scanning electron microscope (SEM) is great for high magnification
images that also contain information about the chemical composition of
the different minerals in meteorites. SEM is also a quick way to do a
qualitative analysis of a sample, say for example, detecting nickel in
iron meteorites with energy dispersive spectroscopy (EDS).

My instrument of choice for definitive ID of stony meteorites is the
electron microprobe. This also has SEM imaging capability. In less the
hour, on a calibrated electron microprobe, I can make a definitive ID,
although unequilbrated chondrites can take more time to narrow down
the possibilities. Some of the key geochemical quantities that help in
categorizing are, Fe/Mn of olivines and pyroxenes, the fayalite and
ferrosilite content of the olivines and pyroxenes, the
anorthite-albite content of plagioclse, and a few other parameters,
plus the percent mineralogy and other textural characteristics.

So for a simple example lunar olivines usually have higher Fe/Mn than
terrestrial basalt olivines. Check out this page's second figure for
an overview of Fe/Mn versus plagioclase content of planetary basalts:
http://www.imca.cc/mars/martian-meteorites.htm

Carl Agee

--
Carl B. Agee
Director and Curator, Institute of Meteoritics
Professor, Earth and Planetary Sciences
MSC03 2050
University of New Mexico
Albuquerque NM 87131-1126

Tel: (505) 750-7172
Fax: (505) 277-3577
Email: agee at unm.edu
http://epswww.unm.edu/iom/pers/agee.html

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Geophysics, meteorites, and Electron microscopy

Barb and Jake Baker bakers5acres at frontiernet.net
Tue Sep 6 10:50:46 EDT 2011

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________________________________
Could someone tell me, in Microscopy 101 language: How is an electron
microscope used in the study of meteorites? Using electron microscopy -
what differences are apparent between meteorites and terrestrial rocks? For
instance what are the microscopy differences between lunar basalt and
terrestrial basalt?

Thanks