As suggested by C. Stevenson, the combination of thermomagnetic
analyses + hysteresis properties should give you a good indication if
you have multiple magnetic phases (e.g. biotite + magnetite
subfabrics) contributing to your AMS (e.g. biotite + magnetite
subfabrics). You may want to consider, if you haven't already,
looking at representative thin sections of your samples for the
presence of inclusions in the mafic silicates or for the presence of
sulfides that could complicate the interpretation further. If your
samples are dominantly paramagnetic, inclusion of magnetite within
biotite can actually yield a net inverse AMS as discussed by
Borradaile and Werner.
Borradaile, G. J. and T. Werner (1994). "Magnetic anisotropy of some
phyllosilicates."
Tectonophysics 235: 223-248.
Cheers and best of luck! Seth
/*--------
Seth C Kruckenberg --> [log in to unmask]
Structure, Tectonics, & Metamorphic Petrology Research Group,
Department of Geology & Geophysics,
108 Pillsbury Hall, University of Minnesota, 310 Pillsbury Dr SE,
Minneapolis, MN, 55455
http://www.umn.edu/~kruc0030
---------*/
On Apr 5, 2009, at 7:46 AM, koushik sen wrote:
> Can anyone provide me some references regarding development of
> composite fabric in granitic rocks i.e. where the mesoscopic
> fabric(magmatic/gneissosity) and magnetic fabric (AMS) fabric are
> discordant? I am presently working on some Proterozoic and Paleozoic
> granitoids of Himalaya and there is discrepancy in their field and AMS
> fabric. This must have been caused by the Tertiary orogeny. Can anyone
> provide information about similar work from other parts of the world?
>
> Best Regards
> Koushik
>
> --
> Dr. Koushik Sen
> Scientist 'B'
> Wadia Institute of Himalayan Geology
> Dehra Dun- 248001
> India
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