Page 197 - Microtectonics

186 6 · Dilatation Sites – Veins, Strain Shadows, Fringes and Boudins

Fig. 6.32. Microboudinage of tourmaline (dark) in a quartzite. Notice boudinage both perpendicular and parallel to the elongate tourmaline
crystals (chocolate tablet boudinage). Quartz recrystallised into large grains overgrowing the necks of the boudins, and was deformed again
as testified by undulose extinction. Fortaleza, NE Brazil. Width of view 4.5 mm. Polars at 45°. (Specimen courtesy Michel Arthaud)

Fig. 6.33. Microboudinage of blue amphibole in a garnet bearing metachert. Notice how, after the boudinage of the light-coloured cores, darker
amphibole overgrew the cores and tended to mend the separated boudins. Metamorphic conditions during boudinage can be estimated from
the changing blue amphibole composition (cf. Fig. 6.34). Sesia Lanzo Zone, Italian Alps. Width of view 4 mm. PPL. (Sample courtesy Leo Minnigh)