Hi all,
I do not think metamorphic rocks should always exhibit a lineation by
default. I couldn't find more than 20 or so mineral lineations in my old,
400 km2, granulite/upper amphibolite facies study area in the Superior
province. These were confined to a special, 3km2 unit. Instead,
mesostructures in the area are dominantly boudinage. These boudinage are
practically equidimensional in the xy plane (ie. nice chocolate
tablets).Check out the attached photo of Pierre Robin admiring a larger
wavelength boudin mold with internal casts of smaller wavelength boudins.
Furthermore, assymetric folds are absent. The only way I can envisage this
group of structures forming is by dominant pure shear. As with Juergen, I
admit that nothing in nature is ever pure except nature itself, so I suppose
there is some simple shear going on there. I just can't see it. Once again,
this all depends on scale. This area may just represent a patch dominated
by pure shear. Any comments from the photo?
Paul M. Evins W tele# +358 8 553 1481
University of Oulu FAX# +358 8 5531484
Dept. of Geology
PL 3000 email: [log in to unmask]
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