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To follow Seth Kruckenburg's suggestion, if you can do thermomag, the original reference (as far as I know) is: Orlicky, O., 1990, Detection of Magnetic Carriers in Rocks - Results of Susceptibility Changes in Powdered Rock Samples Induced by Temperature: Physics of the Earth and Planetary Interiors, v. 63, p. 66-70. Related is: Trindade, R. I. F., T. M. M. Nguema, and J. L. Bouchez, 2001, Thermally enhanced mimetic fabric of magnetite in a biotite granite: Geophysical Research Letters, v. 28, p. 2687-2690. And then in relation to the above we did some heating and high field experiments - we didn't get inverse AMS: Stevenson, C. T. E., W. H. Owens, and D. H. W. Hutton, 2007, Flow lobes in granite: the determination of magma flow direction in the Trawenagh Bay Granite, N. W. Ireland, using anisotropy of magnetic susceptibility: Geological Society of America Bulletin, v 119, p. 1368-1386. Cheers Carl -----Original Message----- From: Tectonics & structural geology discussion list [mailto:[log in to unmask]] On Behalf Of koushik sen Sent: 06 April 2009 05:04 To: [log in to unmask] Subject: Re: on composite fabric in granitoids Thank you everyone. the suggestions and references will be of great help. I dont have MFK here but will definitely do thermal demag to have a idea about the magnetominerology. SEM of biotite (for inclusions) may also be a good idea. Thank you again. Best Regards Koushik On Mon, Apr 6, 2009 at 4:35 AM, Seth Kruckenberg <[log in to unmask]> wrote: > 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 > -- Dr. Koushik Sen Scientist 'B' Wadia Institute of Himalayan Geology Dehra Dun- 248001 India